[PATCH v4 0/4] media: pisp-be: Split jobs creation and scheduling

[PATCH v4 0/4] media: pisp-be: Split jobs creation and scheduling

[Jacopo Mondi]

v3->v4:
- Expand commit message in 2/4 to explain why removing validation in schedule()
  is safe
- Drop ready_lock spinlock
- Use non _irqsave version of safe_guard(spinlock
- Support !CONFIG_PM in 4/4 by calling the enable/disable routines directly
  and adjust pm_runtime usage as suggested by Laurent

v2->v3:
- Mark pispbe_runtime_resume() as __maybe_unused
- Add fixes tags where appropriate

v1->v2:
- Add two patches to address Laurent's comments separately
- use scoped_guard() when possible
- Add patch to fix runtime_pm imbalance

Currently the 'pispbe_schedule()' function does two things:

1) Tries to assemble a job by inspecting all the video node queues
   to make sure all the required buffers are available
2) Submit the job to the hardware

The pispbe_schedule() function is called at:

- video device start_streaming() time
- video device qbuf() time
- irq handler

As assembling a job requires inspecting all queues, it is a rather
time consuming operation which is better not run in IRQ context.

To avoid executing the time consuming job creation in interrupt
context, split the job creation and job scheduling in two distinct
operations. When a well-formed job is created, append it to the
newly introduced 'pispbe->job_queue' where it will be dequeued from
by the scheduling routine.

At start_streaming() and qbuf() time immediately try to schedule a job
if one has been created as the irq handler routine is only called when
a job has completed, and we can't solely rely on it for scheduling new
jobs.

Jacopo Mondi (4):
  media: pisp_be: Drop reference to non-existing function
  media: pisp_be: Remove config validation from schedule()
  media: pisp-be: Split jobs creation and scheduling
  media: pisp_be: Fix pm_runtime underrun in probe

 .../platform/raspberrypi/pisp_be/pisp_be.c    | 190 +++++++++---------
 1 file changed, 93 insertions(+), 97 deletions(-)

--
2.45.2

[PATCH v4 1/4] media: pisp_be: Drop reference to non-existing function

[Jacopo Mondi]

A comment in the pisp_be driver references the
pispbe_schedule_internal() function which doesn't exist.

Drop it.

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
---
 drivers/media/platform/raspberrypi/pisp_be/pisp_be.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
index 65ff2382cffe..8ba1b9f43ba1 100644
--- a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
+++ b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
@@ -368,10 +368,7 @@ static void pispbe_xlate_addrs(struct pispbe_dev *pispbe,
 	ret = pispbe_get_planes_addr(addrs, buf[MAIN_INPUT_NODE],
 				     &pispbe->node[MAIN_INPUT_NODE]);
 	if (ret <= 0) {
-		/*
-		 * This shouldn't happen; pispbe_schedule_internal should insist
-		 * on an input.
-		 */
+		/* Shouldn't happen, we have validated an input is available. */
 		dev_warn(pispbe->dev, "ISP-BE missing input\n");
 		hw_en->bayer_enables = 0;
 		hw_en->rgb_enables = 0;
-- 
2.45.2

[PATCH v4 2/4] media: pisp_be: Remove config validation from schedule()

[Jacopo Mondi]

The config parameters buffer is already validated in
pisp_be_validate_config() at .buf_prepare() time.

However some of the same validations are also performed at
pispbe_schedule() time. In particular the function checks that:

1) config.num_tiles is valid
2) At least one of the BAYER or RGB input is enabled

The input config validation is already performed in
pisp_be_validate_config() and while job.hw_enables is modified by
pispbe_xlate_addrs(), the function only resets the input masks if

- there is no input buffer available, but pispbe_prepare_job() fails
  before calling pispbe_xlate_addrs() in this case
- bayer_enable is 0, but in this case rgb_enable is valid as guaranteed
  by pisp_be_validate_config()
- only outputs are reset in rgb_enable

For this reasons there is no need to repeat the check at
pispbe_schedule() time.

The num_tiles validation can be moved to pisp_be_validate_config() as
well. As num_tiles is a u32 it can'be be < 0, so change the sanity
check accordingly.

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
---
 .../platform/raspberrypi/pisp_be/pisp_be.c    | 25 ++++++-------------
 1 file changed, 7 insertions(+), 18 deletions(-)

diff --git a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
index 8ba1b9f43ba1..41fd68b7757b 100644
--- a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
+++ b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
@@ -588,24 +588,6 @@ static void pispbe_schedule(struct pispbe_dev *pispbe, bool clear_hw_busy)
 	pispbe->hw_busy = true;
 	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
 
-	if (job.config->num_tiles <= 0 ||
-	    job.config->num_tiles > PISP_BACK_END_NUM_TILES ||
-	    !((job.hw_enables.bayer_enables | job.hw_enables.rgb_enables) &
-	      PISP_BE_BAYER_ENABLE_INPUT)) {
-		/*
-		 * Bad job. We can't let it proceed as it could lock up
-		 * the hardware, or worse!
-		 *
-		 * For now, just force num_tiles to 0, which causes the
-		 * H/W to do something bizarre but survivable. It
-		 * increments (started,done) counters by more than 1,
-		 * but we seem to survive...
-		 */
-		dev_dbg(pispbe->dev, "Bad job: invalid number of tiles: %u\n",
-			job.config->num_tiles);
-		job.config->num_tiles = 0;
-	}
-
 	pispbe_queue_job(pispbe, &job);
 
 	return;
@@ -703,6 +685,13 @@ static int pisp_be_validate_config(struct pispbe_dev *pispbe,
 		return -EIO;
 	}
 
+	if (config->num_tiles == 0 ||
+	    config->num_tiles > PISP_BACK_END_NUM_TILES) {
+		dev_dbg(dev, "%s: Invalid number of tiles: %d\n", __func__,
+			config->num_tiles);
+		return -EINVAL;
+	}
+
 	/* Ensure output config strides and buffer sizes match the V4L2 formats. */
 	fmt = &pispbe->node[TDN_OUTPUT_NODE].format;
 	if (bayer_enables & PISP_BE_BAYER_ENABLE_TDN_OUTPUT) {
-- 
2.45.2

[PATCH v4 3/4] media: pisp-be: Split jobs creation and scheduling

[Jacopo Mondi]

Currently the 'pispbe_schedule()' function does two things:

1) Tries to assemble a job by inspecting all the video node queues
   to make sure all the required buffers are available
2) Submit the job to the hardware

The pispbe_schedule() function is called at:

- video device start_streaming() time
- video device qbuf() time
- irq handler

As assembling a job requires inspecting all queues, it is a rather
time consuming operation which is better not run in IRQ context.

To avoid the executing the time consuming job creation in interrupt
context split the job creation and job scheduling in two distinct
operations. When a well-formed job is created, append it to the
newly introduced 'pispbe->job_queue' where it will be dequeued from
by the scheduling routine.

At start_streaming() and qbuf() time immediately try to schedule a job
if one has been created as the irq handler routing is only called when
a job has completed, and we can't solely rely on it for scheduling new
jobs.

As now the per-node 'ready_queue' buffer list is only accessed in vb2
ops callbacks, protected by a mutex, it is not necessary to guard it
with a dedicated spinlock so drop it.

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
---
 .../platform/raspberrypi/pisp_be/pisp_be.c    | 134 ++++++++++--------
 1 file changed, 73 insertions(+), 61 deletions(-)

diff --git a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
index 41fd68b7757b..d614f53f0f68 100644
--- a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
+++ b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
@@ -161,8 +161,6 @@ struct pispbe_node {
 	struct mutex node_lock;
 	/* vb2_queue lock */
 	struct mutex queue_lock;
-	/* Protect pispbe_node->ready_queue and pispbe_buffer->ready_list */
-	spinlock_t ready_lock;
 	struct list_head ready_queue;
 	struct vb2_queue queue;
 	struct v4l2_format format;
@@ -190,6 +188,8 @@ struct pispbe_hw_enables {
 
 /* Records a job configuration and memory addresses. */
 struct pispbe_job_descriptor {
+	struct list_head queue;
+	struct pispbe_buffer *buffers[PISPBE_NUM_NODES];
 	dma_addr_t hw_dma_addrs[N_HW_ADDRESSES];
 	struct pisp_be_tiles_config *config;
 	struct pispbe_hw_enables hw_enables;
@@ -215,8 +215,10 @@ struct pispbe_dev {
 	unsigned int sequence;
 	u32 streaming_map;
 	struct pispbe_job queued_job, running_job;
-	spinlock_t hw_lock; /* protects "hw_busy" flag and streaming_map */
+	/* protects "hw_busy" flag, streaming_map and job_queue */
+	spinlock_t hw_lock;
 	bool hw_busy; /* non-zero if a job is queued or is being started */
+	struct list_head job_queue;
 	int irq;
 	u32 hw_version;
 	u8 done, started;
@@ -440,41 +442,47 @@ static void pispbe_xlate_addrs(struct pispbe_dev *pispbe,
  * For Output0, Output1, Tdn and Stitch, a buffer only needs to be
  * available if the blocks are enabled in the config.
  *
- * Needs to be called with hw_lock held.
+ * If all the buffers required to form a job are available, append the
+ * job descriptor to the job queue to be later queued to the HW.
  *
  * Returns 0 if a job has been successfully prepared, < 0 otherwise.
  */
-static int pispbe_prepare_job(struct pispbe_dev *pispbe,
-			      struct pispbe_job_descriptor *job)
+static int pispbe_prepare_job(struct pispbe_dev *pispbe)
 {
 	struct pispbe_buffer *buf[PISPBE_NUM_NODES] = {};
+	struct pispbe_job_descriptor *job;
+	unsigned int streaming_map;
 	unsigned int config_index;
 	struct pispbe_node *node;
-	unsigned long flags;
 
-	lockdep_assert_held(&pispbe->hw_lock);
+	scoped_guard(spinlock, &pispbe->hw_lock) {
+		static const u32 mask = BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE);
 
-	memset(job, 0, sizeof(struct pispbe_job_descriptor));
+		if ((pispbe->streaming_map & mask) != mask)
+			return -ENODEV;
 
-	if (((BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE)) &
-		pispbe->streaming_map) !=
-			(BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE)))
-		return -ENODEV;
+		/*
+		 * Take a copy of streaming_map: nodes activated after this
+		 * point are ignored when preparing this job.
+		 */
+		streaming_map = pispbe->streaming_map;
+	}
+
+	job = kzalloc(sizeof(*job), GFP_KERNEL);
+	if (!job)
+		return -ENOMEM;
 
 	node = &pispbe->node[CONFIG_NODE];
-	spin_lock_irqsave(&node->ready_lock, flags);
 	buf[CONFIG_NODE] = list_first_entry_or_null(&node->ready_queue,
 						    struct pispbe_buffer,
 						    ready_list);
-	if (buf[CONFIG_NODE]) {
-		list_del(&buf[CONFIG_NODE]->ready_list);
-		pispbe->queued_job.buf[CONFIG_NODE] = buf[CONFIG_NODE];
+	if (!buf[CONFIG_NODE]) {
+		kfree(job);
+		return -ENODEV;
 	}
-	spin_unlock_irqrestore(&node->ready_lock, flags);
 
-	/* Exit early if no config buffer has been queued. */
-	if (!buf[CONFIG_NODE])
-		return -ENODEV;
+	list_del(&buf[CONFIG_NODE]->ready_list);
+	job->buffers[CONFIG_NODE] = buf[CONFIG_NODE];
 
 	config_index = buf[CONFIG_NODE]->vb.vb2_buf.index;
 	job->config = &pispbe->config[config_index];
@@ -495,7 +503,7 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
 			continue;
 
 		buf[i] = NULL;
-		if (!(pispbe->streaming_map & BIT(i)))
+		if (!(streaming_map & BIT(i)))
 			continue;
 
 		if ((!(rgb_en & PISP_BE_RGB_ENABLE_OUTPUT0) &&
@@ -522,25 +530,25 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
 		node = &pispbe->node[i];
 
 		/* Pull a buffer from each V4L2 queue to form the queued job */
-		spin_lock_irqsave(&node->ready_lock, flags);
 		buf[i] = list_first_entry_or_null(&node->ready_queue,
 						  struct pispbe_buffer,
 						  ready_list);
 		if (buf[i]) {
 			list_del(&buf[i]->ready_list);
-			pispbe->queued_job.buf[i] = buf[i];
+			job->buffers[i] = buf[i];
 		}
-		spin_unlock_irqrestore(&node->ready_lock, flags);
 
 		if (!buf[i] && !ignore_buffers)
 			goto err_return_buffers;
 	}
 
-	pispbe->queued_job.valid = true;
-
 	/* Convert buffers to DMA addresses for the hardware */
 	pispbe_xlate_addrs(pispbe, job, buf);
 
+	spin_lock(&pispbe->hw_lock);
+	list_add_tail(&job->queue, &pispbe->job_queue);
+	spin_unlock(&pispbe->hw_lock);
+
 	return 0;
 
 err_return_buffers:
@@ -551,33 +559,39 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
 			continue;
 
 		/* Return the buffer to the ready_list queue */
-		spin_lock_irqsave(&n->ready_lock, flags);
 		list_add(&buf[i]->ready_list, &n->ready_queue);
-		spin_unlock_irqrestore(&n->ready_lock, flags);
 	}
 
-	memset(&pispbe->queued_job, 0, sizeof(pispbe->queued_job));
+	kfree(job);
 
 	return -ENODEV;
 }
 
 static void pispbe_schedule(struct pispbe_dev *pispbe, bool clear_hw_busy)
 {
-	struct pispbe_job_descriptor job;
-	unsigned long flags;
-	int ret;
+	struct pispbe_job_descriptor *job;
 
-	spin_lock_irqsave(&pispbe->hw_lock, flags);
+	scoped_guard(spinlock, &pispbe->hw_lock) {
+		if (clear_hw_busy)
+			pispbe->hw_busy = false;
+
+		if (pispbe->hw_busy)
+			return;
 
-	if (clear_hw_busy)
-		pispbe->hw_busy = false;
+		job = list_first_entry_or_null(&pispbe->job_queue,
+					       struct pispbe_job_descriptor,
+					       queue);
+		if (!job)
+			return;
 
-	if (pispbe->hw_busy)
-		goto unlock_and_return;
+		list_del(&job->queue);
 
-	ret = pispbe_prepare_job(pispbe, &job);
-	if (ret)
-		goto unlock_and_return;
+		for (unsigned int i = 0; i < PISPBE_NUM_NODES; i++)
+			pispbe->queued_job.buf[i] = job->buffers[i];
+		 pispbe->queued_job.valid = true;
+
+		pispbe->hw_busy = true;
+	}
 
 	/*
 	 * We can kick the job off without the hw_lock, as this can
@@ -585,16 +599,8 @@ static void pispbe_schedule(struct pispbe_dev *pispbe, bool clear_hw_busy)
 	 * only when the following job has been queued and an interrupt
 	 * is rised.
 	 */
-	pispbe->hw_busy = true;
-	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
-
-	pispbe_queue_job(pispbe, &job);
-
-	return;
-
-unlock_and_return:
-	/* No job has been queued, just release the lock and return. */
-	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
+	pispbe_queue_job(pispbe, job);
+	kfree(job);
 }
 
 static void pispbe_isr_jobdone(struct pispbe_dev *pispbe,
@@ -846,18 +852,16 @@ static void pispbe_node_buffer_queue(struct vb2_buffer *buf)
 		container_of(vbuf, struct pispbe_buffer, vb);
 	struct pispbe_node *node = vb2_get_drv_priv(buf->vb2_queue);
 	struct pispbe_dev *pispbe = node->pispbe;
-	unsigned long flags;
 
 	dev_dbg(pispbe->dev, "%s: for node %s\n", __func__, NODE_NAME(node));
-	spin_lock_irqsave(&node->ready_lock, flags);
 	list_add_tail(&buffer->ready_list, &node->ready_queue);
-	spin_unlock_irqrestore(&node->ready_lock, flags);
 
 	/*
 	 * Every time we add a buffer, check if there's now some work for the hw
 	 * to do.
 	 */
-	pispbe_schedule(pispbe, false);
+	if (!pispbe_prepare_job(pispbe))
+		pispbe_schedule(pispbe, false);
 }
 
 static int pispbe_node_start_streaming(struct vb2_queue *q, unsigned int count)
@@ -883,7 +887,8 @@ static int pispbe_node_start_streaming(struct vb2_queue *q, unsigned int count)
 		node->pispbe->streaming_map);
 
 	/* Maybe we're ready to run. */
-	pispbe_schedule(pispbe, false);
+	if (!pispbe_prepare_job(pispbe))
+		pispbe_schedule(pispbe, false);
 
 	return 0;
 
@@ -917,9 +922,6 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
 	dev_dbg(pispbe->dev, "%s: for node %s\n", __func__, NODE_NAME(node));
 	spin_lock_irqsave(&pispbe->hw_lock, flags);
 	do {
-		unsigned long flags1;
-
-		spin_lock_irqsave(&node->ready_lock, flags1);
 		buf = list_first_entry_or_null(&node->ready_queue,
 					       struct pispbe_buffer,
 					       ready_list);
@@ -927,7 +929,6 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
 			list_del(&buf->ready_list);
 			vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
 		}
-		spin_unlock_irqrestore(&node->ready_lock, flags1);
 	} while (buf);
 	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
 
@@ -935,6 +936,16 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
 
 	spin_lock_irqsave(&pispbe->hw_lock, flags);
 	pispbe->streaming_map &= ~BIT(node->id);
+
+	/* Release all jobs once all nodes have stopped streaming. */
+	if (pispbe->streaming_map == 0) {
+		struct pispbe_job_descriptor *job, *temp;
+
+		list_for_each_entry_safe(job, temp, &pispbe->job_queue, queue) {
+			list_del(&job->queue);
+			kfree(job);
+		}
+	}
 	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
 
 	pm_runtime_mark_last_busy(pispbe->dev);
@@ -1393,7 +1404,6 @@ static int pispbe_init_node(struct pispbe_dev *pispbe, unsigned int id)
 	mutex_init(&node->node_lock);
 	mutex_init(&node->queue_lock);
 	INIT_LIST_HEAD(&node->ready_queue);
-	spin_lock_init(&node->ready_lock);
 
 	node->format.type = node->buf_type;
 	pispbe_node_def_fmt(node);
@@ -1677,6 +1687,8 @@ static int pispbe_probe(struct platform_device *pdev)
 	if (!pispbe)
 		return -ENOMEM;
 
+	INIT_LIST_HEAD(&pispbe->job_queue);
+
 	dev_set_drvdata(&pdev->dev, pispbe);
 	pispbe->dev = &pdev->dev;
 	platform_set_drvdata(pdev, pispbe);
-- 
2.45.2

[PATCH v4 4/4] media: pisp_be: Fix pm_runtime underrun in probe

[Jacopo Mondi]

During the probe() routine, the driver needs to power up the interface
in order to identify and initialize the hardware and it later suspends
it at the end of probe().

The driver erroneously resumes the interface by calling the
pispbe_runtime_resume() function directly but suspends it by
calling pm_runtime_put_autosuspend().

This causes a PM usage count imbalance at probe time, notified by the
runtime_pm framework with the below message in the system log:

 pispbe 1000880000.pisp_be: Runtime PM usage count underflow!

Fix this by suspending the interface using pm_runtime_idle() which
doesn't decrease the pm_runtime usage count and inform the PM framework
that the device is active by calling pm_runtime_set_active().

Adjust the pispbe_remove() function as well to disable
the pm_runtime in the correct order,

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>

---
v3->v4:
- Instead of using pm_runtime for resuming, suspend using
  pm_runtime_idle() to support !CONFIG_PM

v2->v3:
- Mark pispbe_runtime_resume() as __maybe_unused as reported by
  the kernel test robot <lkp@intel.com>
---
 .../platform/raspberrypi/pisp_be/pisp_be.c    | 26 +++++++++----------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
index d614f53f0f68..1c19ca946bd4 100644
--- a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
+++ b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
@@ -1720,36 +1720,32 @@ static int pispbe_probe(struct platform_device *pdev)
 				     "Failed to get clock");
 
 	/* Hardware initialisation */
-	pm_runtime_set_autosuspend_delay(pispbe->dev, 200);
-	pm_runtime_use_autosuspend(pispbe->dev);
-	pm_runtime_enable(pispbe->dev);
-
 	ret = pispbe_runtime_resume(pispbe->dev);
 	if (ret)
-		goto pm_runtime_disable_err;
+		return ret;
 
 	pispbe->hw_busy = false;
 	spin_lock_init(&pispbe->hw_lock);
 	ret = pispbe_hw_init(pispbe);
 	if (ret)
-		goto pm_runtime_suspend_err;
+		goto runtime_suspend_err;
 
 	ret = pispbe_init_devices(pispbe);
 	if (ret)
 		goto disable_devs_err;
 
-	pm_runtime_mark_last_busy(pispbe->dev);
-	pm_runtime_put_autosuspend(pispbe->dev);
+	pm_runtime_set_autosuspend_delay(pispbe->dev, 200);
+	pm_runtime_use_autosuspend(pispbe->dev);
+	pm_runtime_set_active(pispbe->dev);
+	pm_runtime_enable(pispbe->dev);
+	pm_runtime_idle(pispbe->dev);
 
 	return 0;
 
 disable_devs_err:
 	pispbe_destroy_devices(pispbe);
-pm_runtime_suspend_err:
+runtime_suspend_err:
 	pispbe_runtime_suspend(pispbe->dev);
-pm_runtime_disable_err:
-	pm_runtime_dont_use_autosuspend(pispbe->dev);
-	pm_runtime_disable(pispbe->dev);
 
 	return ret;
 }
@@ -1760,9 +1756,11 @@ static void pispbe_remove(struct platform_device *pdev)
 
 	pispbe_destroy_devices(pispbe);
 
-	pispbe_runtime_suspend(pispbe->dev);
 	pm_runtime_dont_use_autosuspend(pispbe->dev);
-	pm_runtime_disable(pispbe->dev);
+        pm_runtime_disable(pispbe->dev);
+        if (!pm_runtime_status_suspended(pispbe->dev))
+                pispbe_runtime_suspend(pispbe->dev);
+        pm_runtime_set_suspended(pispbe->dev);
 }
 
 static const struct dev_pm_ops pispbe_pm_ops = {
-- 
2.45.2

Re: [PATCH v4 1/4] media: pisp_be: Drop reference to non-existing function

[Laurent Pinchart]

Hi Jacopo,

Thank you for the patch.

On Mon, Sep 02, 2024 at 01:24:03PM +0200, Jacopo Mondi wrote:
> A comment in the pisp_be driver references the
> pispbe_schedule_internal() function which doesn't exist.
> 
> Drop it.
> 
> Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> ---
>  drivers/media/platform/raspberrypi/pisp_be/pisp_be.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> index 65ff2382cffe..8ba1b9f43ba1 100644
> --- a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> +++ b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> @@ -368,10 +368,7 @@ static void pispbe_xlate_addrs(struct pispbe_dev *pispbe,
>  	ret = pispbe_get_planes_addr(addrs, buf[MAIN_INPUT_NODE],
>  				     &pispbe->node[MAIN_INPUT_NODE]);
>  	if (ret <= 0) {
> -		/*
> -		 * This shouldn't happen; pispbe_schedule_internal should insist
> -		 * on an input.
> -		 */
> +		/* Shouldn't happen, we have validated an input is available. */
>  		dev_warn(pispbe->dev, "ISP-BE missing input\n");
>  		hw_en->bayer_enables = 0;
>  		hw_en->rgb_enables = 0;

-- 
Regards,

Laurent Pinchart

Re: [PATCH v4 2/4] media: pisp_be: Remove config validation from schedule()

[Laurent Pinchart]

Hi Jacopo,

Thank you for the patch.

On Mon, Sep 02, 2024 at 01:24:04PM +0200, Jacopo Mondi wrote:
> The config parameters buffer is already validated in
> pisp_be_validate_config() at .buf_prepare() time.
> 
> However some of the same validations are also performed at
> pispbe_schedule() time. In particular the function checks that:
> 
> 1) config.num_tiles is valid
> 2) At least one of the BAYER or RGB input is enabled
> 
> The input config validation is already performed in
> pisp_be_validate_config() and while job.hw_enables is modified by
> pispbe_xlate_addrs(), the function only resets the input masks if
> 
> - there is no input buffer available, but pispbe_prepare_job() fails
>   before calling pispbe_xlate_addrs() in this case
> - bayer_enable is 0, but in this case rgb_enable is valid as guaranteed
>   by pisp_be_validate_config()
> - only outputs are reset in rgb_enable
> 
> For this reasons there is no need to repeat the check at
> pispbe_schedule() time.
> 
> The num_tiles validation can be moved to pisp_be_validate_config() as
> well. As num_tiles is a u32 it can'be be < 0, so change the sanity
> check accordingly.
> 
> Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> ---
>  .../platform/raspberrypi/pisp_be/pisp_be.c    | 25 ++++++-------------
>  1 file changed, 7 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> index 8ba1b9f43ba1..41fd68b7757b 100644
> --- a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> +++ b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> @@ -588,24 +588,6 @@ static void pispbe_schedule(struct pispbe_dev *pispbe, bool clear_hw_busy)
>  	pispbe->hw_busy = true;
>  	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
>  
> -	if (job.config->num_tiles <= 0 ||
> -	    job.config->num_tiles > PISP_BACK_END_NUM_TILES ||
> -	    !((job.hw_enables.bayer_enables | job.hw_enables.rgb_enables) &
> -	      PISP_BE_BAYER_ENABLE_INPUT)) {
> -		/*
> -		 * Bad job. We can't let it proceed as it could lock up
> -		 * the hardware, or worse!
> -		 *
> -		 * For now, just force num_tiles to 0, which causes the
> -		 * H/W to do something bizarre but survivable. It
> -		 * increments (started,done) counters by more than 1,
> -		 * but we seem to survive...
> -		 */
> -		dev_dbg(pispbe->dev, "Bad job: invalid number of tiles: %u\n",
> -			job.config->num_tiles);
> -		job.config->num_tiles = 0;
> -	}
> -
>  	pispbe_queue_job(pispbe, &job);
>  
>  	return;
> @@ -703,6 +685,13 @@ static int pisp_be_validate_config(struct pispbe_dev *pispbe,
>  		return -EIO;
>  	}
>  
> +	if (config->num_tiles == 0 ||
> +	    config->num_tiles > PISP_BACK_END_NUM_TILES) {
> +		dev_dbg(dev, "%s: Invalid number of tiles: %d\n", __func__,
> +			config->num_tiles);
> +		return -EINVAL;
> +	}
> +
>  	/* Ensure output config strides and buffer sizes match the V4L2 formats. */
>  	fmt = &pispbe->node[TDN_OUTPUT_NODE].format;
>  	if (bayer_enables & PISP_BE_BAYER_ENABLE_TDN_OUTPUT) {

-- 
Regards,

Laurent Pinchart

Re: [PATCH v4 4/4] media: pisp_be: Fix pm_runtime underrun in probe

[Laurent Pinchart]

Hi Jacopo,

Thank you for the patch.

On Mon, Sep 02, 2024 at 01:24:06PM +0200, Jacopo Mondi wrote:
> During the probe() routine, the driver needs to power up the interface
> in order to identify and initialize the hardware and it later suspends
> it at the end of probe().
> 
> The driver erroneously resumes the interface by calling the
> pispbe_runtime_resume() function directly but suspends it by
> calling pm_runtime_put_autosuspend().
> 
> This causes a PM usage count imbalance at probe time, notified by the
> runtime_pm framework with the below message in the system log:
> 
>  pispbe 1000880000.pisp_be: Runtime PM usage count underflow!
> 
> Fix this by suspending the interface using pm_runtime_idle() which
> doesn't decrease the pm_runtime usage count and inform the PM framework
> that the device is active by calling pm_runtime_set_active().
> 
> Adjust the pispbe_remove() function as well to disable
> the pm_runtime in the correct order,

s/,$/./

> Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
> 
> ---
> v3->v4:
> - Instead of using pm_runtime for resuming, suspend using
>   pm_runtime_idle() to support !CONFIG_PM
> 
> v2->v3:
> - Mark pispbe_runtime_resume() as __maybe_unused as reported by
>   the kernel test robot <lkp@intel.com>
> ---
>  .../platform/raspberrypi/pisp_be/pisp_be.c    | 26 +++++++++----------
>  1 file changed, 12 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> index d614f53f0f68..1c19ca946bd4 100644
> --- a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> +++ b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> @@ -1720,36 +1720,32 @@ static int pispbe_probe(struct platform_device *pdev)
>  				     "Failed to get clock");
>  
>  	/* Hardware initialisation */
> -	pm_runtime_set_autosuspend_delay(pispbe->dev, 200);
> -	pm_runtime_use_autosuspend(pispbe->dev);
> -	pm_runtime_enable(pispbe->dev);
> -
>  	ret = pispbe_runtime_resume(pispbe->dev);
>  	if (ret)
> -		goto pm_runtime_disable_err;
> +		return ret;
>  
>  	pispbe->hw_busy = false;
>  	spin_lock_init(&pispbe->hw_lock);
>  	ret = pispbe_hw_init(pispbe);
>  	if (ret)
> -		goto pm_runtime_suspend_err;
> +		goto runtime_suspend_err;
>  
>  	ret = pispbe_init_devices(pispbe);
>  	if (ret)
>  		goto disable_devs_err;
>  
> -	pm_runtime_mark_last_busy(pispbe->dev);
> -	pm_runtime_put_autosuspend(pispbe->dev);
> +	pm_runtime_set_autosuspend_delay(pispbe->dev, 200);
> +	pm_runtime_use_autosuspend(pispbe->dev);
> +	pm_runtime_set_active(pispbe->dev);
> +	pm_runtime_enable(pispbe->dev);
> +	pm_runtime_idle(pispbe->dev);
>  
>  	return 0;
>  
>  disable_devs_err:

It would be nice to rename the error labels to start with err_, like
commonly done (in another patch of course).

>  	pispbe_destroy_devices(pispbe);
> -pm_runtime_suspend_err:
> +runtime_suspend_err:
>  	pispbe_runtime_suspend(pispbe->dev);
> -pm_runtime_disable_err:
> -	pm_runtime_dont_use_autosuspend(pispbe->dev);
> -	pm_runtime_disable(pispbe->dev);
>  
>  	return ret;
>  }
> @@ -1760,9 +1756,11 @@ static void pispbe_remove(struct platform_device *pdev)
>  
>  	pispbe_destroy_devices(pispbe);
>  
> -	pispbe_runtime_suspend(pispbe->dev);
>  	pm_runtime_dont_use_autosuspend(pispbe->dev);
> -	pm_runtime_disable(pispbe->dev);
> +        pm_runtime_disable(pispbe->dev);
> +        if (!pm_runtime_status_suspended(pispbe->dev))
> +                pispbe_runtime_suspend(pispbe->dev);
> +        pm_runtime_set_suspended(pispbe->dev);

Wrong indentation, you're using spaces instead of tabs.

With those issues fixed,

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

>  }
>  
>  static const struct dev_pm_ops pispbe_pm_ops = {

-- 
Regards,

Laurent Pinchart

Re: [PATCH v4 4/4] media: pisp_be: Fix pm_runtime underrun in probe

[Jacopo Mondi]

Hi Laurent,

On Tue, Sep 03, 2024 at 02:13:16AM GMT, Laurent Pinchart wrote:
> Hi Jacopo,
>
> Thank you for the patch.
>
> On Mon, Sep 02, 2024 at 01:24:06PM +0200, Jacopo Mondi wrote:
> > During the probe() routine, the driver needs to power up the interface
> > in order to identify and initialize the hardware and it later suspends
> > it at the end of probe().
> >
> > The driver erroneously resumes the interface by calling the
> > pispbe_runtime_resume() function directly but suspends it by
> > calling pm_runtime_put_autosuspend().
> >
> > This causes a PM usage count imbalance at probe time, notified by the
> > runtime_pm framework with the below message in the system log:
> >
> >  pispbe 1000880000.pisp_be: Runtime PM usage count underflow!
> >
> > Fix this by suspending the interface using pm_runtime_idle() which
> > doesn't decrease the pm_runtime usage count and inform the PM framework
> > that the device is active by calling pm_runtime_set_active().
> >
> > Adjust the pispbe_remove() function as well to disable
> > the pm_runtime in the correct order,
>
> s/,$/./
>
> > Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
> >
> > ---
> > v3->v4:
> > - Instead of using pm_runtime for resuming, suspend using
> >   pm_runtime_idle() to support !CONFIG_PM
> >
> > v2->v3:
> > - Mark pispbe_runtime_resume() as __maybe_unused as reported by
> >   the kernel test robot <lkp@intel.com>
> > ---
> >  .../platform/raspberrypi/pisp_be/pisp_be.c    | 26 +++++++++----------
> >  1 file changed, 12 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> > index d614f53f0f68..1c19ca946bd4 100644
> > --- a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> > +++ b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> > @@ -1720,36 +1720,32 @@ static int pispbe_probe(struct platform_device *pdev)
> >  				     "Failed to get clock");
> >
> >  	/* Hardware initialisation */
> > -	pm_runtime_set_autosuspend_delay(pispbe->dev, 200);
> > -	pm_runtime_use_autosuspend(pispbe->dev);
> > -	pm_runtime_enable(pispbe->dev);
> > -
> >  	ret = pispbe_runtime_resume(pispbe->dev);
> >  	if (ret)
> > -		goto pm_runtime_disable_err;
> > +		return ret;
> >
> >  	pispbe->hw_busy = false;
> >  	spin_lock_init(&pispbe->hw_lock);
> >  	ret = pispbe_hw_init(pispbe);
> >  	if (ret)
> > -		goto pm_runtime_suspend_err;
> > +		goto runtime_suspend_err;
> >
> >  	ret = pispbe_init_devices(pispbe);
> >  	if (ret)
> >  		goto disable_devs_err;
> >
> > -	pm_runtime_mark_last_busy(pispbe->dev);
> > -	pm_runtime_put_autosuspend(pispbe->dev);
> > +	pm_runtime_set_autosuspend_delay(pispbe->dev, 200);
> > +	pm_runtime_use_autosuspend(pispbe->dev);
> > +	pm_runtime_set_active(pispbe->dev);
> > +	pm_runtime_enable(pispbe->dev);
> > +	pm_runtime_idle(pispbe->dev);
> >
> >  	return 0;
> >
> >  disable_devs_err:
>
> It would be nice to rename the error labels to start with err_, like
> commonly done (in another patch of course).
>
> >  	pispbe_destroy_devices(pispbe);
> > -pm_runtime_suspend_err:
> > +runtime_suspend_err:
> >  	pispbe_runtime_suspend(pispbe->dev);
> > -pm_runtime_disable_err:
> > -	pm_runtime_dont_use_autosuspend(pispbe->dev);
> > -	pm_runtime_disable(pispbe->dev);
> >
> >  	return ret;
> >  }
> > @@ -1760,9 +1756,11 @@ static void pispbe_remove(struct platform_device *pdev)
> >
> >  	pispbe_destroy_devices(pispbe);
> >
> > -	pispbe_runtime_suspend(pispbe->dev);
> >  	pm_runtime_dont_use_autosuspend(pispbe->dev);
> > -	pm_runtime_disable(pispbe->dev);
> > +        pm_runtime_disable(pispbe->dev);
> > +        if (!pm_runtime_status_suspended(pispbe->dev))
> > +                pispbe_runtime_suspend(pispbe->dev);
> > +        pm_runtime_set_suspended(pispbe->dev);
>
> Wrong indentation, you're using spaces instead of tabs.

Oh crabs, how did I missed that ?

>
> With those issues fixed,
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Thanks

>
> >  }
> >
> >  static const struct dev_pm_ops pispbe_pm_ops = {
>
> --
> Regards,
>
> Laurent Pinchart

Re: [PATCH v4 3/4] media: pisp-be: Split jobs creation and scheduling

[Laurent Pinchart]

Hi Jacopo,

Thank you for the patch.

I just noticed the subject line writes "pisp-be" while all other patches
in the series use "pisp_be".

On Mon, Sep 02, 2024 at 01:24:05PM +0200, Jacopo Mondi wrote:
> Currently the 'pispbe_schedule()' function does two things:
> 
> 1) Tries to assemble a job by inspecting all the video node queues
>    to make sure all the required buffers are available
> 2) Submit the job to the hardware
> 
> The pispbe_schedule() function is called at:
> 
> - video device start_streaming() time
> - video device qbuf() time
> - irq handler
> 
> As assembling a job requires inspecting all queues, it is a rather
> time consuming operation which is better not run in IRQ context.
> 
> To avoid the executing the time consuming job creation in interrupt
> context split the job creation and job scheduling in two distinct
> operations. When a well-formed job is created, append it to the
> newly introduced 'pispbe->job_queue' where it will be dequeued from
> by the scheduling routine.
> 
> At start_streaming() and qbuf() time immediately try to schedule a job
> if one has been created as the irq handler routing is only called when
> a job has completed, and we can't solely rely on it for scheduling new
> jobs.
> 
> As now the per-node 'ready_queue' buffer list is only accessed in vb2
> ops callbacks, protected by a mutex, it is not necessary to guard it
> with a dedicated spinlock so drop it.
> 
> Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
> ---
>  .../platform/raspberrypi/pisp_be/pisp_be.c    | 134 ++++++++++--------
>  1 file changed, 73 insertions(+), 61 deletions(-)
> 
> diff --git a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> index 41fd68b7757b..d614f53f0f68 100644
> --- a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> +++ b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> @@ -161,8 +161,6 @@ struct pispbe_node {
>  	struct mutex node_lock;
>  	/* vb2_queue lock */
>  	struct mutex queue_lock;
> -	/* Protect pispbe_node->ready_queue and pispbe_buffer->ready_list */
> -	spinlock_t ready_lock;
>  	struct list_head ready_queue;
>  	struct vb2_queue queue;
>  	struct v4l2_format format;
> @@ -190,6 +188,8 @@ struct pispbe_hw_enables {
>  
>  /* Records a job configuration and memory addresses. */
>  struct pispbe_job_descriptor {
> +	struct list_head queue;
> +	struct pispbe_buffer *buffers[PISPBE_NUM_NODES];
>  	dma_addr_t hw_dma_addrs[N_HW_ADDRESSES];
>  	struct pisp_be_tiles_config *config;
>  	struct pispbe_hw_enables hw_enables;
> @@ -215,8 +215,10 @@ struct pispbe_dev {
>  	unsigned int sequence;
>  	u32 streaming_map;
>  	struct pispbe_job queued_job, running_job;
> -	spinlock_t hw_lock; /* protects "hw_busy" flag and streaming_map */
> +	/* protects "hw_busy" flag, streaming_map and job_queue */
> +	spinlock_t hw_lock;
>  	bool hw_busy; /* non-zero if a job is queued or is being started */
> +	struct list_head job_queue;
>  	int irq;
>  	u32 hw_version;
>  	u8 done, started;
> @@ -440,41 +442,47 @@ static void pispbe_xlate_addrs(struct pispbe_dev *pispbe,
>   * For Output0, Output1, Tdn and Stitch, a buffer only needs to be
>   * available if the blocks are enabled in the config.
>   *
> - * Needs to be called with hw_lock held.
> + * If all the buffers required to form a job are available, append the
> + * job descriptor to the job queue to be later queued to the HW.
>   *
>   * Returns 0 if a job has been successfully prepared, < 0 otherwise.
>   */
> -static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> -			      struct pispbe_job_descriptor *job)
> +static int pispbe_prepare_job(struct pispbe_dev *pispbe)
>  {
>  	struct pispbe_buffer *buf[PISPBE_NUM_NODES] = {};
> +	struct pispbe_job_descriptor *job;
> +	unsigned int streaming_map;
>  	unsigned int config_index;
>  	struct pispbe_node *node;
> -	unsigned long flags;
>  
> -	lockdep_assert_held(&pispbe->hw_lock);
> +	scoped_guard(spinlock, &pispbe->hw_lock) {

I think I've mis-communicated the locking requirements. This spinlock is
taken in both non-IRQ contexts (here) and in mixed IRQ and non-IRQ
contexts (pispbe_schedule(), called from both IRQ context in
pispbe_isr() and non-IRQ context in pispbe_node_buffer_queue() and
pispbe_node_start_streaming()).

This means that the non-IRQ contexts should use spinlock_irq(), and the
mixed contexts should use spinlock_irqsave().

> +		static const u32 mask = BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE);
>  
> -	memset(job, 0, sizeof(struct pispbe_job_descriptor));
> +		if ((pispbe->streaming_map & mask) != mask)
> +			return -ENODEV;
>  
> -	if (((BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE)) &
> -		pispbe->streaming_map) !=
> -			(BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE)))
> -		return -ENODEV;
> +		/*
> +		 * Take a copy of streaming_map: nodes activated after this
> +		 * point are ignored when preparing this job.
> +		 */
> +		streaming_map = pispbe->streaming_map;
> +	}
> +
> +	job = kzalloc(sizeof(*job), GFP_KERNEL);
> +	if (!job)
> +		return -ENOMEM;
>  
>  	node = &pispbe->node[CONFIG_NODE];
> -	spin_lock_irqsave(&node->ready_lock, flags);
>  	buf[CONFIG_NODE] = list_first_entry_or_null(&node->ready_queue,
>  						    struct pispbe_buffer,
>  						    ready_list);
> -	if (buf[CONFIG_NODE]) {
> -		list_del(&buf[CONFIG_NODE]->ready_list);
> -		pispbe->queued_job.buf[CONFIG_NODE] = buf[CONFIG_NODE];
> +	if (!buf[CONFIG_NODE]) {
> +		kfree(job);
> +		return -ENODEV;
>  	}
> -	spin_unlock_irqrestore(&node->ready_lock, flags);
>  
> -	/* Exit early if no config buffer has been queued. */
> -	if (!buf[CONFIG_NODE])
> -		return -ENODEV;
> +	list_del(&buf[CONFIG_NODE]->ready_list);
> +	job->buffers[CONFIG_NODE] = buf[CONFIG_NODE];
>  
>  	config_index = buf[CONFIG_NODE]->vb.vb2_buf.index;
>  	job->config = &pispbe->config[config_index];
> @@ -495,7 +503,7 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
>  			continue;
>  
>  		buf[i] = NULL;
> -		if (!(pispbe->streaming_map & BIT(i)))
> +		if (!(streaming_map & BIT(i)))
>  			continue;
>  
>  		if ((!(rgb_en & PISP_BE_RGB_ENABLE_OUTPUT0) &&
> @@ -522,25 +530,25 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
>  		node = &pispbe->node[i];
>  
>  		/* Pull a buffer from each V4L2 queue to form the queued job */
> -		spin_lock_irqsave(&node->ready_lock, flags);
>  		buf[i] = list_first_entry_or_null(&node->ready_queue,
>  						  struct pispbe_buffer,
>  						  ready_list);
>  		if (buf[i]) {
>  			list_del(&buf[i]->ready_list);
> -			pispbe->queued_job.buf[i] = buf[i];
> +			job->buffers[i] = buf[i];
>  		}
> -		spin_unlock_irqrestore(&node->ready_lock, flags);
>  
>  		if (!buf[i] && !ignore_buffers)
>  			goto err_return_buffers;
>  	}
>  
> -	pispbe->queued_job.valid = true;
> -
>  	/* Convert buffers to DMA addresses for the hardware */
>  	pispbe_xlate_addrs(pispbe, job, buf);
>  
> +	spin_lock(&pispbe->hw_lock);
> +	list_add_tail(&job->queue, &pispbe->job_queue);
> +	spin_unlock(&pispbe->hw_lock);
> +
>  	return 0;
>  
>  err_return_buffers:
> @@ -551,33 +559,39 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
>  			continue;
>  
>  		/* Return the buffer to the ready_list queue */
> -		spin_lock_irqsave(&n->ready_lock, flags);
>  		list_add(&buf[i]->ready_list, &n->ready_queue);
> -		spin_unlock_irqrestore(&n->ready_lock, flags);
>  	}
>  
> -	memset(&pispbe->queued_job, 0, sizeof(pispbe->queued_job));
> +	kfree(job);
>  
>  	return -ENODEV;
>  }
>  
>  static void pispbe_schedule(struct pispbe_dev *pispbe, bool clear_hw_busy)
>  {
> -	struct pispbe_job_descriptor job;
> -	unsigned long flags;
> -	int ret;
> +	struct pispbe_job_descriptor *job;
>  
> -	spin_lock_irqsave(&pispbe->hw_lock, flags);
> +	scoped_guard(spinlock, &pispbe->hw_lock) {
> +		if (clear_hw_busy)
> +			pispbe->hw_busy = false;
> +
> +		if (pispbe->hw_busy)
> +			return;
>  
> -	if (clear_hw_busy)
> -		pispbe->hw_busy = false;
> +		job = list_first_entry_or_null(&pispbe->job_queue,
> +					       struct pispbe_job_descriptor,
> +					       queue);
> +		if (!job)
> +			return;
>  
> -	if (pispbe->hw_busy)
> -		goto unlock_and_return;
> +		list_del(&job->queue);
>  
> -	ret = pispbe_prepare_job(pispbe, &job);
> -	if (ret)
> -		goto unlock_and_return;
> +		for (unsigned int i = 0; i < PISPBE_NUM_NODES; i++)
> +			pispbe->queued_job.buf[i] = job->buffers[i];
> +		 pispbe->queued_job.valid = true;
> +
> +		pispbe->hw_busy = true;
> +	}
>  
>  	/*
>  	 * We can kick the job off without the hw_lock, as this can
> @@ -585,16 +599,8 @@ static void pispbe_schedule(struct pispbe_dev *pispbe, bool clear_hw_busy)
>  	 * only when the following job has been queued and an interrupt
>  	 * is rised.
>  	 */
> -	pispbe->hw_busy = true;
> -	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> -
> -	pispbe_queue_job(pispbe, &job);
> -
> -	return;
> -
> -unlock_and_return:
> -	/* No job has been queued, just release the lock and return. */
> -	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> +	pispbe_queue_job(pispbe, job);
> +	kfree(job);
>  }
>  
>  static void pispbe_isr_jobdone(struct pispbe_dev *pispbe,
> @@ -846,18 +852,16 @@ static void pispbe_node_buffer_queue(struct vb2_buffer *buf)
>  		container_of(vbuf, struct pispbe_buffer, vb);
>  	struct pispbe_node *node = vb2_get_drv_priv(buf->vb2_queue);
>  	struct pispbe_dev *pispbe = node->pispbe;
> -	unsigned long flags;
>  
>  	dev_dbg(pispbe->dev, "%s: for node %s\n", __func__, NODE_NAME(node));
> -	spin_lock_irqsave(&node->ready_lock, flags);
>  	list_add_tail(&buffer->ready_list, &node->ready_queue);
> -	spin_unlock_irqrestore(&node->ready_lock, flags);
>  
>  	/*
>  	 * Every time we add a buffer, check if there's now some work for the hw
>  	 * to do.
>  	 */
> -	pispbe_schedule(pispbe, false);
> +	if (!pispbe_prepare_job(pispbe))
> +		pispbe_schedule(pispbe, false);
>  }
>  
>  static int pispbe_node_start_streaming(struct vb2_queue *q, unsigned int count)
> @@ -883,7 +887,8 @@ static int pispbe_node_start_streaming(struct vb2_queue *q, unsigned int count)
>  		node->pispbe->streaming_map);
>  
>  	/* Maybe we're ready to run. */
> -	pispbe_schedule(pispbe, false);
> +	if (!pispbe_prepare_job(pispbe))
> +		pispbe_schedule(pispbe, false);
>  
>  	return 0;
>  
> @@ -917,9 +922,6 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
>  	dev_dbg(pispbe->dev, "%s: for node %s\n", __func__, NODE_NAME(node));
>  	spin_lock_irqsave(&pispbe->hw_lock, flags);

Is the lock needed here ? And in the err_return_buffers error path in
pispbe_node_start_streaming() ? Both seem to touch the ready_queue only,
which isn't protected by the hw_lock.

>  	do {
> -		unsigned long flags1;
> -
> -		spin_lock_irqsave(&node->ready_lock, flags1);
>  		buf = list_first_entry_or_null(&node->ready_queue,
>  					       struct pispbe_buffer,
>  					       ready_list);
> @@ -927,7 +929,6 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
>  			list_del(&buf->ready_list);
>  			vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
>  		}
> -		spin_unlock_irqrestore(&node->ready_lock, flags1);
>  	} while (buf);
>  	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
>  
> @@ -935,6 +936,16 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
>  
>  	spin_lock_irqsave(&pispbe->hw_lock, flags);
>  	pispbe->streaming_map &= ~BIT(node->id);
> +
> +	/* Release all jobs once all nodes have stopped streaming. */
> +	if (pispbe->streaming_map == 0) {
> +		struct pispbe_job_descriptor *job, *temp;
> +
> +		list_for_each_entry_safe(job, temp, &pispbe->job_queue, queue) {
> +			list_del(&job->queue);
> +			kfree(job);
> +		}

I think this can be done outside of the lock.

> +	}
>  	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
>  
>  	pm_runtime_mark_last_busy(pispbe->dev);
> @@ -1393,7 +1404,6 @@ static int pispbe_init_node(struct pispbe_dev *pispbe, unsigned int id)
>  	mutex_init(&node->node_lock);
>  	mutex_init(&node->queue_lock);
>  	INIT_LIST_HEAD(&node->ready_queue);
> -	spin_lock_init(&node->ready_lock);
>  
>  	node->format.type = node->buf_type;
>  	pispbe_node_def_fmt(node);
> @@ -1677,6 +1687,8 @@ static int pispbe_probe(struct platform_device *pdev)
>  	if (!pispbe)
>  		return -ENOMEM;
>  
> +	INIT_LIST_HEAD(&pispbe->job_queue);
> +
>  	dev_set_drvdata(&pdev->dev, pispbe);
>  	pispbe->dev = &pdev->dev;
>  	platform_set_drvdata(pdev, pispbe);

-- 
Regards,

Laurent Pinchart

Re: [PATCH v4 3/4] media: pisp-be: Split jobs creation and scheduling

[Jacopo Mondi]

Hi Laurent

On Tue, Sep 03, 2024 at 03:19:36PM GMT, Laurent Pinchart wrote:
> Hi Jacopo,
>
> Thank you for the patch.
>
> I just noticed the subject line writes "pisp-be" while all other patches
> in the series use "pisp_be".
>
> On Mon, Sep 02, 2024 at 01:24:05PM +0200, Jacopo Mondi wrote:
> > Currently the 'pispbe_schedule()' function does two things:
> >
> > 1) Tries to assemble a job by inspecting all the video node queues
> >    to make sure all the required buffers are available
> > 2) Submit the job to the hardware
> >
> > The pispbe_schedule() function is called at:
> >
> > - video device start_streaming() time
> > - video device qbuf() time
> > - irq handler
> >
> > As assembling a job requires inspecting all queues, it is a rather
> > time consuming operation which is better not run in IRQ context.
> >
> > To avoid the executing the time consuming job creation in interrupt
> > context split the job creation and job scheduling in two distinct
> > operations. When a well-formed job is created, append it to the
> > newly introduced 'pispbe->job_queue' where it will be dequeued from
> > by the scheduling routine.
> >
> > At start_streaming() and qbuf() time immediately try to schedule a job
> > if one has been created as the irq handler routing is only called when
> > a job has completed, and we can't solely rely on it for scheduling new
> > jobs.
> >
> > As now the per-node 'ready_queue' buffer list is only accessed in vb2
> > ops callbacks, protected by a mutex, it is not necessary to guard it
> > with a dedicated spinlock so drop it.
> >
> > Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
> > ---
> >  .../platform/raspberrypi/pisp_be/pisp_be.c    | 134 ++++++++++--------
> >  1 file changed, 73 insertions(+), 61 deletions(-)
> >
> > diff --git a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> > index 41fd68b7757b..d614f53f0f68 100644
> > --- a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> > +++ b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> > @@ -161,8 +161,6 @@ struct pispbe_node {
> >  	struct mutex node_lock;
> >  	/* vb2_queue lock */
> >  	struct mutex queue_lock;
> > -	/* Protect pispbe_node->ready_queue and pispbe_buffer->ready_list */
> > -	spinlock_t ready_lock;
> >  	struct list_head ready_queue;
> >  	struct vb2_queue queue;
> >  	struct v4l2_format format;
> > @@ -190,6 +188,8 @@ struct pispbe_hw_enables {
> >
> >  /* Records a job configuration and memory addresses. */
> >  struct pispbe_job_descriptor {
> > +	struct list_head queue;
> > +	struct pispbe_buffer *buffers[PISPBE_NUM_NODES];
> >  	dma_addr_t hw_dma_addrs[N_HW_ADDRESSES];
> >  	struct pisp_be_tiles_config *config;
> >  	struct pispbe_hw_enables hw_enables;
> > @@ -215,8 +215,10 @@ struct pispbe_dev {
> >  	unsigned int sequence;
> >  	u32 streaming_map;
> >  	struct pispbe_job queued_job, running_job;
> > -	spinlock_t hw_lock; /* protects "hw_busy" flag and streaming_map */
> > +	/* protects "hw_busy" flag, streaming_map and job_queue */
> > +	spinlock_t hw_lock;
> >  	bool hw_busy; /* non-zero if a job is queued or is being started */
> > +	struct list_head job_queue;
> >  	int irq;
> >  	u32 hw_version;
> >  	u8 done, started;
> > @@ -440,41 +442,47 @@ static void pispbe_xlate_addrs(struct pispbe_dev *pispbe,
> >   * For Output0, Output1, Tdn and Stitch, a buffer only needs to be
> >   * available if the blocks are enabled in the config.
> >   *
> > - * Needs to be called with hw_lock held.
> > + * If all the buffers required to form a job are available, append the
> > + * job descriptor to the job queue to be later queued to the HW.
> >   *
> >   * Returns 0 if a job has been successfully prepared, < 0 otherwise.
> >   */
> > -static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> > -			      struct pispbe_job_descriptor *job)
> > +static int pispbe_prepare_job(struct pispbe_dev *pispbe)
> >  {
> >  	struct pispbe_buffer *buf[PISPBE_NUM_NODES] = {};
> > +	struct pispbe_job_descriptor *job;
> > +	unsigned int streaming_map;
> >  	unsigned int config_index;
> >  	struct pispbe_node *node;
> > -	unsigned long flags;
> >
> > -	lockdep_assert_held(&pispbe->hw_lock);
> > +	scoped_guard(spinlock, &pispbe->hw_lock) {
>
> I think I've mis-communicated the locking requirements. This spinlock is
> taken in both non-IRQ contexts (here) and in mixed IRQ and non-IRQ
> contexts (pispbe_schedule(), called from both IRQ context in
> pispbe_isr() and non-IRQ context in pispbe_node_buffer_queue() and
> pispbe_node_start_streaming()).
>
> This means that the non-IRQ contexts should use spinlock_irq(), and the
> mixed contexts should use spinlock_irqsave().
>

Yeah sorry, I admit I hadn't put much attention to this

> > +		static const u32 mask = BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE);
> >
> > -	memset(job, 0, sizeof(struct pispbe_job_descriptor));
> > +		if ((pispbe->streaming_map & mask) != mask)
> > +			return -ENODEV;
> >
> > -	if (((BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE)) &
> > -		pispbe->streaming_map) !=
> > -			(BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE)))
> > -		return -ENODEV;
> > +		/*
> > +		 * Take a copy of streaming_map: nodes activated after this
> > +		 * point are ignored when preparing this job.
> > +		 */
> > +		streaming_map = pispbe->streaming_map;
> > +	}
> > +
> > +	job = kzalloc(sizeof(*job), GFP_KERNEL);
> > +	if (!job)
> > +		return -ENOMEM;
> >
> >  	node = &pispbe->node[CONFIG_NODE];
> > -	spin_lock_irqsave(&node->ready_lock, flags);
> >  	buf[CONFIG_NODE] = list_first_entry_or_null(&node->ready_queue,
> >  						    struct pispbe_buffer,
> >  						    ready_list);
> > -	if (buf[CONFIG_NODE]) {
> > -		list_del(&buf[CONFIG_NODE]->ready_list);
> > -		pispbe->queued_job.buf[CONFIG_NODE] = buf[CONFIG_NODE];
> > +	if (!buf[CONFIG_NODE]) {
> > +		kfree(job);
> > +		return -ENODEV;
> >  	}
> > -	spin_unlock_irqrestore(&node->ready_lock, flags);
> >
> > -	/* Exit early if no config buffer has been queued. */
> > -	if (!buf[CONFIG_NODE])
> > -		return -ENODEV;
> > +	list_del(&buf[CONFIG_NODE]->ready_list);
> > +	job->buffers[CONFIG_NODE] = buf[CONFIG_NODE];
> >
> >  	config_index = buf[CONFIG_NODE]->vb.vb2_buf.index;
> >  	job->config = &pispbe->config[config_index];
> > @@ -495,7 +503,7 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> >  			continue;
> >
> >  		buf[i] = NULL;
> > -		if (!(pispbe->streaming_map & BIT(i)))
> > +		if (!(streaming_map & BIT(i)))
> >  			continue;
> >
> >  		if ((!(rgb_en & PISP_BE_RGB_ENABLE_OUTPUT0) &&
> > @@ -522,25 +530,25 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> >  		node = &pispbe->node[i];
> >
> >  		/* Pull a buffer from each V4L2 queue to form the queued job */
> > -		spin_lock_irqsave(&node->ready_lock, flags);
> >  		buf[i] = list_first_entry_or_null(&node->ready_queue,
> >  						  struct pispbe_buffer,
> >  						  ready_list);
> >  		if (buf[i]) {
> >  			list_del(&buf[i]->ready_list);
> > -			pispbe->queued_job.buf[i] = buf[i];
> > +			job->buffers[i] = buf[i];
> >  		}
> > -		spin_unlock_irqrestore(&node->ready_lock, flags);
> >
> >  		if (!buf[i] && !ignore_buffers)
> >  			goto err_return_buffers;
> >  	}
> >
> > -	pispbe->queued_job.valid = true;
> > -
> >  	/* Convert buffers to DMA addresses for the hardware */
> >  	pispbe_xlate_addrs(pispbe, job, buf);
> >
> > +	spin_lock(&pispbe->hw_lock);
> > +	list_add_tail(&job->queue, &pispbe->job_queue);
> > +	spin_unlock(&pispbe->hw_lock);
> > +
> >  	return 0;
> >
> >  err_return_buffers:
> > @@ -551,33 +559,39 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> >  			continue;
> >
> >  		/* Return the buffer to the ready_list queue */
> > -		spin_lock_irqsave(&n->ready_lock, flags);
> >  		list_add(&buf[i]->ready_list, &n->ready_queue);
> > -		spin_unlock_irqrestore(&n->ready_lock, flags);
> >  	}
> >
> > -	memset(&pispbe->queued_job, 0, sizeof(pispbe->queued_job));
> > +	kfree(job);
> >
> >  	return -ENODEV;
> >  }
> >
> >  static void pispbe_schedule(struct pispbe_dev *pispbe, bool clear_hw_busy)
> >  {
> > -	struct pispbe_job_descriptor job;
> > -	unsigned long flags;
> > -	int ret;
> > +	struct pispbe_job_descriptor *job;
> >
> > -	spin_lock_irqsave(&pispbe->hw_lock, flags);
> > +	scoped_guard(spinlock, &pispbe->hw_lock) {
> > +		if (clear_hw_busy)
> > +			pispbe->hw_busy = false;
> > +
> > +		if (pispbe->hw_busy)
> > +			return;
> >
> > -	if (clear_hw_busy)
> > -		pispbe->hw_busy = false;
> > +		job = list_first_entry_or_null(&pispbe->job_queue,
> > +					       struct pispbe_job_descriptor,
> > +					       queue);
> > +		if (!job)
> > +			return;
> >
> > -	if (pispbe->hw_busy)
> > -		goto unlock_and_return;
> > +		list_del(&job->queue);
> >
> > -	ret = pispbe_prepare_job(pispbe, &job);
> > -	if (ret)
> > -		goto unlock_and_return;
> > +		for (unsigned int i = 0; i < PISPBE_NUM_NODES; i++)
> > +			pispbe->queued_job.buf[i] = job->buffers[i];
> > +		 pispbe->queued_job.valid = true;
> > +
> > +		pispbe->hw_busy = true;
> > +	}
> >
> >  	/*
> >  	 * We can kick the job off without the hw_lock, as this can
> > @@ -585,16 +599,8 @@ static void pispbe_schedule(struct pispbe_dev *pispbe, bool clear_hw_busy)
> >  	 * only when the following job has been queued and an interrupt
> >  	 * is rised.
> >  	 */
> > -	pispbe->hw_busy = true;
> > -	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> > -
> > -	pispbe_queue_job(pispbe, &job);
> > -
> > -	return;
> > -
> > -unlock_and_return:
> > -	/* No job has been queued, just release the lock and return. */
> > -	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> > +	pispbe_queue_job(pispbe, job);
> > +	kfree(job);
> >  }
> >
> >  static void pispbe_isr_jobdone(struct pispbe_dev *pispbe,
> > @@ -846,18 +852,16 @@ static void pispbe_node_buffer_queue(struct vb2_buffer *buf)
> >  		container_of(vbuf, struct pispbe_buffer, vb);
> >  	struct pispbe_node *node = vb2_get_drv_priv(buf->vb2_queue);
> >  	struct pispbe_dev *pispbe = node->pispbe;
> > -	unsigned long flags;
> >
> >  	dev_dbg(pispbe->dev, "%s: for node %s\n", __func__, NODE_NAME(node));
> > -	spin_lock_irqsave(&node->ready_lock, flags);
> >  	list_add_tail(&buffer->ready_list, &node->ready_queue);
> > -	spin_unlock_irqrestore(&node->ready_lock, flags);
> >
> >  	/*
> >  	 * Every time we add a buffer, check if there's now some work for the hw
> >  	 * to do.
> >  	 */
> > -	pispbe_schedule(pispbe, false);
> > +	if (!pispbe_prepare_job(pispbe))
> > +		pispbe_schedule(pispbe, false);
> >  }
> >
> >  static int pispbe_node_start_streaming(struct vb2_queue *q, unsigned int count)
> > @@ -883,7 +887,8 @@ static int pispbe_node_start_streaming(struct vb2_queue *q, unsigned int count)
> >  		node->pispbe->streaming_map);
> >
> >  	/* Maybe we're ready to run. */
> > -	pispbe_schedule(pispbe, false);
> > +	if (!pispbe_prepare_job(pispbe))
> > +		pispbe_schedule(pispbe, false);
> >
> >  	return 0;
> >
> > @@ -917,9 +922,6 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
> >  	dev_dbg(pispbe->dev, "%s: for node %s\n", __func__, NODE_NAME(node));
> >  	spin_lock_irqsave(&pispbe->hw_lock, flags);
>
> Is the lock needed here ? And in the err_return_buffers error path in
> pispbe_node_start_streaming() ? Both seem to touch the ready_queue only,
> which isn't protected by the hw_lock.
>

No the lock is not needed, and as this is not irq context I should
switch both stop_streaming() and start_streaming() to use
spink_lock_irq()

> >  	do {
> > -		unsigned long flags1;
> > -
> > -		spin_lock_irqsave(&node->ready_lock, flags1);
> >  		buf = list_first_entry_or_null(&node->ready_queue,
> >  					       struct pispbe_buffer,
> >  					       ready_list);
> > @@ -927,7 +929,6 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
> >  			list_del(&buf->ready_list);
> >  			vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
> >  		}
> > -		spin_unlock_irqrestore(&node->ready_lock, flags1);
> >  	} while (buf);
> >  	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> >
> > @@ -935,6 +936,16 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
> >
> >  	spin_lock_irqsave(&pispbe->hw_lock, flags);
> >  	pispbe->streaming_map &= ~BIT(node->id);
> > +
> > +	/* Release all jobs once all nodes have stopped streaming. */
> > +	if (pispbe->streaming_map == 0) {
> > +		struct pispbe_job_descriptor *job, *temp;
> > +
> > +		list_for_each_entry_safe(job, temp, &pispbe->job_queue, queue) {
> > +			list_del(&job->queue);
> > +			kfree(job);
> > +		}
>
> I think this can be done outside of the lock.
>

Does it ? The job queue is accessed by the irq handler. As we
stop the interface -after- having cleared the job queue here, I would
keep this sequence inside the lock to be honest.

> > +	}
> >  	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> >
> >  	pm_runtime_mark_last_busy(pispbe->dev);
> > @@ -1393,7 +1404,6 @@ static int pispbe_init_node(struct pispbe_dev *pispbe, unsigned int id)
> >  	mutex_init(&node->node_lock);
> >  	mutex_init(&node->queue_lock);
> >  	INIT_LIST_HEAD(&node->ready_queue);
> > -	spin_lock_init(&node->ready_lock);
> >
> >  	node->format.type = node->buf_type;
> >  	pispbe_node_def_fmt(node);
> > @@ -1677,6 +1687,8 @@ static int pispbe_probe(struct platform_device *pdev)
> >  	if (!pispbe)
> >  		return -ENOMEM;
> >
> > +	INIT_LIST_HEAD(&pispbe->job_queue);
> > +
> >  	dev_set_drvdata(&pdev->dev, pispbe);
> >  	pispbe->dev = &pdev->dev;
> >  	platform_set_drvdata(pdev, pispbe);
>
> --
> Regards,
>
> Laurent Pinchart

Re: [PATCH v4 3/4] media: pisp-be: Split jobs creation and scheduling

[Laurent Pinchart]

On Wed, Sep 04, 2024 at 09:21:45AM +0200, Jacopo Mondi wrote:
> Hi Laurent
> 
> On Tue, Sep 03, 2024 at 03:19:36PM GMT, Laurent Pinchart wrote:
> > Hi Jacopo,
> >
> > Thank you for the patch.
> >
> > I just noticed the subject line writes "pisp-be" while all other patches
> > in the series use "pisp_be".
> >
> > On Mon, Sep 02, 2024 at 01:24:05PM +0200, Jacopo Mondi wrote:
> > > Currently the 'pispbe_schedule()' function does two things:
> > >
> > > 1) Tries to assemble a job by inspecting all the video node queues
> > >    to make sure all the required buffers are available
> > > 2) Submit the job to the hardware
> > >
> > > The pispbe_schedule() function is called at:
> > >
> > > - video device start_streaming() time
> > > - video device qbuf() time
> > > - irq handler
> > >
> > > As assembling a job requires inspecting all queues, it is a rather
> > > time consuming operation which is better not run in IRQ context.
> > >
> > > To avoid the executing the time consuming job creation in interrupt
> > > context split the job creation and job scheduling in two distinct
> > > operations. When a well-formed job is created, append it to the
> > > newly introduced 'pispbe->job_queue' where it will be dequeued from
> > > by the scheduling routine.
> > >
> > > At start_streaming() and qbuf() time immediately try to schedule a job
> > > if one has been created as the irq handler routing is only called when
> > > a job has completed, and we can't solely rely on it for scheduling new
> > > jobs.
> > >
> > > As now the per-node 'ready_queue' buffer list is only accessed in vb2
> > > ops callbacks, protected by a mutex, it is not necessary to guard it
> > > with a dedicated spinlock so drop it.
> > >
> > > Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
> > > ---
> > >  .../platform/raspberrypi/pisp_be/pisp_be.c    | 134 ++++++++++--------
> > >  1 file changed, 73 insertions(+), 61 deletions(-)
> > >
> > > diff --git a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> > > index 41fd68b7757b..d614f53f0f68 100644
> > > --- a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> > > +++ b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> > > @@ -161,8 +161,6 @@ struct pispbe_node {
> > >  	struct mutex node_lock;
> > >  	/* vb2_queue lock */
> > >  	struct mutex queue_lock;
> > > -	/* Protect pispbe_node->ready_queue and pispbe_buffer->ready_list */
> > > -	spinlock_t ready_lock;
> > >  	struct list_head ready_queue;
> > >  	struct vb2_queue queue;
> > >  	struct v4l2_format format;
> > > @@ -190,6 +188,8 @@ struct pispbe_hw_enables {
> > >
> > >  /* Records a job configuration and memory addresses. */
> > >  struct pispbe_job_descriptor {
> > > +	struct list_head queue;
> > > +	struct pispbe_buffer *buffers[PISPBE_NUM_NODES];
> > >  	dma_addr_t hw_dma_addrs[N_HW_ADDRESSES];
> > >  	struct pisp_be_tiles_config *config;
> > >  	struct pispbe_hw_enables hw_enables;
> > > @@ -215,8 +215,10 @@ struct pispbe_dev {
> > >  	unsigned int sequence;
> > >  	u32 streaming_map;
> > >  	struct pispbe_job queued_job, running_job;
> > > -	spinlock_t hw_lock; /* protects "hw_busy" flag and streaming_map */
> > > +	/* protects "hw_busy" flag, streaming_map and job_queue */
> > > +	spinlock_t hw_lock;
> > >  	bool hw_busy; /* non-zero if a job is queued or is being started */
> > > +	struct list_head job_queue;
> > >  	int irq;
> > >  	u32 hw_version;
> > >  	u8 done, started;
> > > @@ -440,41 +442,47 @@ static void pispbe_xlate_addrs(struct pispbe_dev *pispbe,
> > >   * For Output0, Output1, Tdn and Stitch, a buffer only needs to be
> > >   * available if the blocks are enabled in the config.
> > >   *
> > > - * Needs to be called with hw_lock held.
> > > + * If all the buffers required to form a job are available, append the
> > > + * job descriptor to the job queue to be later queued to the HW.
> > >   *
> > >   * Returns 0 if a job has been successfully prepared, < 0 otherwise.
> > >   */
> > > -static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> > > -			      struct pispbe_job_descriptor *job)
> > > +static int pispbe_prepare_job(struct pispbe_dev *pispbe)
> > >  {
> > >  	struct pispbe_buffer *buf[PISPBE_NUM_NODES] = {};
> > > +	struct pispbe_job_descriptor *job;
> > > +	unsigned int streaming_map;
> > >  	unsigned int config_index;
> > >  	struct pispbe_node *node;
> > > -	unsigned long flags;
> > >
> > > -	lockdep_assert_held(&pispbe->hw_lock);
> > > +	scoped_guard(spinlock, &pispbe->hw_lock) {
> >
> > I think I've mis-communicated the locking requirements. This spinlock is
> > taken in both non-IRQ contexts (here) and in mixed IRQ and non-IRQ
> > contexts (pispbe_schedule(), called from both IRQ context in
> > pispbe_isr() and non-IRQ context in pispbe_node_buffer_queue() and
> > pispbe_node_start_streaming()).
> >
> > This means that the non-IRQ contexts should use spinlock_irq(), and the
> > mixed contexts should use spinlock_irqsave().
> >
> 
> Yeah sorry, I admit I hadn't put much attention to this
> 
> > > +		static const u32 mask = BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE);
> > >
> > > -	memset(job, 0, sizeof(struct pispbe_job_descriptor));
> > > +		if ((pispbe->streaming_map & mask) != mask)
> > > +			return -ENODEV;
> > >
> > > -	if (((BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE)) &
> > > -		pispbe->streaming_map) !=
> > > -			(BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE)))
> > > -		return -ENODEV;
> > > +		/*
> > > +		 * Take a copy of streaming_map: nodes activated after this
> > > +		 * point are ignored when preparing this job.
> > > +		 */
> > > +		streaming_map = pispbe->streaming_map;
> > > +	}
> > > +
> > > +	job = kzalloc(sizeof(*job), GFP_KERNEL);
> > > +	if (!job)
> > > +		return -ENOMEM;
> > >
> > >  	node = &pispbe->node[CONFIG_NODE];
> > > -	spin_lock_irqsave(&node->ready_lock, flags);
> > >  	buf[CONFIG_NODE] = list_first_entry_or_null(&node->ready_queue,
> > >  						    struct pispbe_buffer,
> > >  						    ready_list);
> > > -	if (buf[CONFIG_NODE]) {
> > > -		list_del(&buf[CONFIG_NODE]->ready_list);
> > > -		pispbe->queued_job.buf[CONFIG_NODE] = buf[CONFIG_NODE];
> > > +	if (!buf[CONFIG_NODE]) {
> > > +		kfree(job);
> > > +		return -ENODEV;
> > >  	}
> > > -	spin_unlock_irqrestore(&node->ready_lock, flags);
> > >
> > > -	/* Exit early if no config buffer has been queued. */
> > > -	if (!buf[CONFIG_NODE])
> > > -		return -ENODEV;
> > > +	list_del(&buf[CONFIG_NODE]->ready_list);
> > > +	job->buffers[CONFIG_NODE] = buf[CONFIG_NODE];
> > >
> > >  	config_index = buf[CONFIG_NODE]->vb.vb2_buf.index;
> > >  	job->config = &pispbe->config[config_index];
> > > @@ -495,7 +503,7 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> > >  			continue;
> > >
> > >  		buf[i] = NULL;
> > > -		if (!(pispbe->streaming_map & BIT(i)))
> > > +		if (!(streaming_map & BIT(i)))
> > >  			continue;
> > >
> > >  		if ((!(rgb_en & PISP_BE_RGB_ENABLE_OUTPUT0) &&
> > > @@ -522,25 +530,25 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> > >  		node = &pispbe->node[i];
> > >
> > >  		/* Pull a buffer from each V4L2 queue to form the queued job */
> > > -		spin_lock_irqsave(&node->ready_lock, flags);
> > >  		buf[i] = list_first_entry_or_null(&node->ready_queue,
> > >  						  struct pispbe_buffer,
> > >  						  ready_list);
> > >  		if (buf[i]) {
> > >  			list_del(&buf[i]->ready_list);
> > > -			pispbe->queued_job.buf[i] = buf[i];
> > > +			job->buffers[i] = buf[i];
> > >  		}
> > > -		spin_unlock_irqrestore(&node->ready_lock, flags);
> > >
> > >  		if (!buf[i] && !ignore_buffers)
> > >  			goto err_return_buffers;
> > >  	}
> > >
> > > -	pispbe->queued_job.valid = true;
> > > -
> > >  	/* Convert buffers to DMA addresses for the hardware */
> > >  	pispbe_xlate_addrs(pispbe, job, buf);
> > >
> > > +	spin_lock(&pispbe->hw_lock);
> > > +	list_add_tail(&job->queue, &pispbe->job_queue);
> > > +	spin_unlock(&pispbe->hw_lock);
> > > +
> > >  	return 0;
> > >
> > >  err_return_buffers:
> > > @@ -551,33 +559,39 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> > >  			continue;
> > >
> > >  		/* Return the buffer to the ready_list queue */
> > > -		spin_lock_irqsave(&n->ready_lock, flags);
> > >  		list_add(&buf[i]->ready_list, &n->ready_queue);
> > > -		spin_unlock_irqrestore(&n->ready_lock, flags);
> > >  	}
> > >
> > > -	memset(&pispbe->queued_job, 0, sizeof(pispbe->queued_job));
> > > +	kfree(job);
> > >
> > >  	return -ENODEV;
> > >  }
> > >
> > >  static void pispbe_schedule(struct pispbe_dev *pispbe, bool clear_hw_busy)
> > >  {
> > > -	struct pispbe_job_descriptor job;
> > > -	unsigned long flags;
> > > -	int ret;
> > > +	struct pispbe_job_descriptor *job;
> > >
> > > -	spin_lock_irqsave(&pispbe->hw_lock, flags);
> > > +	scoped_guard(spinlock, &pispbe->hw_lock) {
> > > +		if (clear_hw_busy)
> > > +			pispbe->hw_busy = false;
> > > +
> > > +		if (pispbe->hw_busy)
> > > +			return;
> > >
> > > -	if (clear_hw_busy)
> > > -		pispbe->hw_busy = false;
> > > +		job = list_first_entry_or_null(&pispbe->job_queue,
> > > +					       struct pispbe_job_descriptor,
> > > +					       queue);
> > > +		if (!job)
> > > +			return;
> > >
> > > -	if (pispbe->hw_busy)
> > > -		goto unlock_and_return;
> > > +		list_del(&job->queue);
> > >
> > > -	ret = pispbe_prepare_job(pispbe, &job);
> > > -	if (ret)
> > > -		goto unlock_and_return;
> > > +		for (unsigned int i = 0; i < PISPBE_NUM_NODES; i++)
> > > +			pispbe->queued_job.buf[i] = job->buffers[i];
> > > +		 pispbe->queued_job.valid = true;
> > > +
> > > +		pispbe->hw_busy = true;
> > > +	}
> > >
> > >  	/*
> > >  	 * We can kick the job off without the hw_lock, as this can
> > > @@ -585,16 +599,8 @@ static void pispbe_schedule(struct pispbe_dev *pispbe, bool clear_hw_busy)
> > >  	 * only when the following job has been queued and an interrupt
> > >  	 * is rised.
> > >  	 */
> > > -	pispbe->hw_busy = true;
> > > -	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> > > -
> > > -	pispbe_queue_job(pispbe, &job);
> > > -
> > > -	return;
> > > -
> > > -unlock_and_return:
> > > -	/* No job has been queued, just release the lock and return. */
> > > -	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> > > +	pispbe_queue_job(pispbe, job);
> > > +	kfree(job);
> > >  }
> > >
> > >  static void pispbe_isr_jobdone(struct pispbe_dev *pispbe,
> > > @@ -846,18 +852,16 @@ static void pispbe_node_buffer_queue(struct vb2_buffer *buf)
> > >  		container_of(vbuf, struct pispbe_buffer, vb);
> > >  	struct pispbe_node *node = vb2_get_drv_priv(buf->vb2_queue);
> > >  	struct pispbe_dev *pispbe = node->pispbe;
> > > -	unsigned long flags;
> > >
> > >  	dev_dbg(pispbe->dev, "%s: for node %s\n", __func__, NODE_NAME(node));
> > > -	spin_lock_irqsave(&node->ready_lock, flags);
> > >  	list_add_tail(&buffer->ready_list, &node->ready_queue);
> > > -	spin_unlock_irqrestore(&node->ready_lock, flags);
> > >
> > >  	/*
> > >  	 * Every time we add a buffer, check if there's now some work for the hw
> > >  	 * to do.
> > >  	 */
> > > -	pispbe_schedule(pispbe, false);
> > > +	if (!pispbe_prepare_job(pispbe))
> > > +		pispbe_schedule(pispbe, false);
> > >  }
> > >
> > >  static int pispbe_node_start_streaming(struct vb2_queue *q, unsigned int count)
> > > @@ -883,7 +887,8 @@ static int pispbe_node_start_streaming(struct vb2_queue *q, unsigned int count)
> > >  		node->pispbe->streaming_map);
> > >
> > >  	/* Maybe we're ready to run. */
> > > -	pispbe_schedule(pispbe, false);
> > > +	if (!pispbe_prepare_job(pispbe))
> > > +		pispbe_schedule(pispbe, false);
> > >
> > >  	return 0;
> > >
> > > @@ -917,9 +922,6 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
> > >  	dev_dbg(pispbe->dev, "%s: for node %s\n", __func__, NODE_NAME(node));
> > >  	spin_lock_irqsave(&pispbe->hw_lock, flags);
> >
> > Is the lock needed here ? And in the err_return_buffers error path in
> > pispbe_node_start_streaming() ? Both seem to touch the ready_queue only,
> > which isn't protected by the hw_lock.
> 
> No the lock is not needed, and as this is not irq context I should
> switch both stop_streaming() and start_streaming() to use
> spink_lock_irq()
> 
> > >  	do {
> > > -		unsigned long flags1;
> > > -
> > > -		spin_lock_irqsave(&node->ready_lock, flags1);
> > >  		buf = list_first_entry_or_null(&node->ready_queue,
> > >  					       struct pispbe_buffer,
> > >  					       ready_list);
> > > @@ -927,7 +929,6 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
> > >  			list_del(&buf->ready_list);
> > >  			vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
> > >  		}
> > > -		spin_unlock_irqrestore(&node->ready_lock, flags1);
> > >  	} while (buf);
> > >  	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> > >
> > > @@ -935,6 +936,16 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
> > >
> > >  	spin_lock_irqsave(&pispbe->hw_lock, flags);
> > >  	pispbe->streaming_map &= ~BIT(node->id);
> > > +
> > > +	/* Release all jobs once all nodes have stopped streaming. */
> > > +	if (pispbe->streaming_map == 0) {
> > > +		struct pispbe_job_descriptor *job, *temp;
> > > +
> > > +		list_for_each_entry_safe(job, temp, &pispbe->job_queue, queue) {
> > > +			list_del(&job->queue);
> > > +			kfree(job);
> > > +		}
> >
> > I think this can be done outside of the lock.
> >
> 
> Does it ? The job queue is accessed by the irq handler. As we
> stop the interface -after- having cleared the job queue here, I would
> keep this sequence inside the lock to be honest.

Ah yes you right. I'm not sure what I missed.

What you can do here, though, is to splice the job_queue to a local list
with the lock, and then iterate over the local list and free the jobs
without the lock.

> > > +	}
> > >  	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> > >
> > >  	pm_runtime_mark_last_busy(pispbe->dev);
> > > @@ -1393,7 +1404,6 @@ static int pispbe_init_node(struct pispbe_dev *pispbe, unsigned int id)
> > >  	mutex_init(&node->node_lock);
> > >  	mutex_init(&node->queue_lock);
> > >  	INIT_LIST_HEAD(&node->ready_queue);
> > > -	spin_lock_init(&node->ready_lock);
> > >
> > >  	node->format.type = node->buf_type;
> > >  	pispbe_node_def_fmt(node);
> > > @@ -1677,6 +1687,8 @@ static int pispbe_probe(struct platform_device *pdev)
> > >  	if (!pispbe)
> > >  		return -ENOMEM;
> > >
> > > +	INIT_LIST_HEAD(&pispbe->job_queue);
> > > +
> > >  	dev_set_drvdata(&pdev->dev, pispbe);
> > >  	pispbe->dev = &pdev->dev;
> > >  	platform_set_drvdata(pdev, pispbe);

-- 
Regards,

Laurent Pinchart

Re: [PATCH v4 3/4] media: pisp-be: Split jobs creation and scheduling

[Jacopo Mondi]

Hi Laurent

On Wed, Sep 04, 2024 at 10:53:02AM GMT, Laurent Pinchart wrote:
> On Wed, Sep 04, 2024 at 09:21:45AM +0200, Jacopo Mondi wrote:
> > Hi Laurent
> >
> > On Tue, Sep 03, 2024 at 03:19:36PM GMT, Laurent Pinchart wrote:
> > > Hi Jacopo,
> > >
> > > Thank you for the patch.
> > >
> > > I just noticed the subject line writes "pisp-be" while all other patches
> > > in the series use "pisp_be".
> > >
> > > On Mon, Sep 02, 2024 at 01:24:05PM +0200, Jacopo Mondi wrote:
> > > > Currently the 'pispbe_schedule()' function does two things:
> > > >
> > > > 1) Tries to assemble a job by inspecting all the video node queues
> > > >    to make sure all the required buffers are available
> > > > 2) Submit the job to the hardware
> > > >
> > > > The pispbe_schedule() function is called at:
> > > >
> > > > - video device start_streaming() time
> > > > - video device qbuf() time
> > > > - irq handler
> > > >
> > > > As assembling a job requires inspecting all queues, it is a rather
> > > > time consuming operation which is better not run in IRQ context.
> > > >
> > > > To avoid the executing the time consuming job creation in interrupt
> > > > context split the job creation and job scheduling in two distinct
> > > > operations. When a well-formed job is created, append it to the
> > > > newly introduced 'pispbe->job_queue' where it will be dequeued from
> > > > by the scheduling routine.
> > > >
> > > > At start_streaming() and qbuf() time immediately try to schedule a job
> > > > if one has been created as the irq handler routing is only called when
> > > > a job has completed, and we can't solely rely on it for scheduling new
> > > > jobs.
> > > >
> > > > As now the per-node 'ready_queue' buffer list is only accessed in vb2
> > > > ops callbacks, protected by a mutex, it is not necessary to guard it
> > > > with a dedicated spinlock so drop it.
> > > >
> > > > Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
> > > > ---
> > > >  .../platform/raspberrypi/pisp_be/pisp_be.c    | 134 ++++++++++--------
> > > >  1 file changed, 73 insertions(+), 61 deletions(-)
> > > >
> > > > diff --git a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> > > > index 41fd68b7757b..d614f53f0f68 100644
> > > > --- a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> > > > +++ b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> > > > @@ -161,8 +161,6 @@ struct pispbe_node {
> > > >  	struct mutex node_lock;
> > > >  	/* vb2_queue lock */
> > > >  	struct mutex queue_lock;
> > > > -	/* Protect pispbe_node->ready_queue and pispbe_buffer->ready_list */
> > > > -	spinlock_t ready_lock;
> > > >  	struct list_head ready_queue;
> > > >  	struct vb2_queue queue;
> > > >  	struct v4l2_format format;
> > > > @@ -190,6 +188,8 @@ struct pispbe_hw_enables {
> > > >
> > > >  /* Records a job configuration and memory addresses. */
> > > >  struct pispbe_job_descriptor {
> > > > +	struct list_head queue;
> > > > +	struct pispbe_buffer *buffers[PISPBE_NUM_NODES];
> > > >  	dma_addr_t hw_dma_addrs[N_HW_ADDRESSES];
> > > >  	struct pisp_be_tiles_config *config;
> > > >  	struct pispbe_hw_enables hw_enables;
> > > > @@ -215,8 +215,10 @@ struct pispbe_dev {
> > > >  	unsigned int sequence;
> > > >  	u32 streaming_map;
> > > >  	struct pispbe_job queued_job, running_job;
> > > > -	spinlock_t hw_lock; /* protects "hw_busy" flag and streaming_map */
> > > > +	/* protects "hw_busy" flag, streaming_map and job_queue */
> > > > +	spinlock_t hw_lock;
> > > >  	bool hw_busy; /* non-zero if a job is queued or is being started */
> > > > +	struct list_head job_queue;
> > > >  	int irq;
> > > >  	u32 hw_version;
> > > >  	u8 done, started;
> > > > @@ -440,41 +442,47 @@ static void pispbe_xlate_addrs(struct pispbe_dev *pispbe,
> > > >   * For Output0, Output1, Tdn and Stitch, a buffer only needs to be
> > > >   * available if the blocks are enabled in the config.
> > > >   *
> > > > - * Needs to be called with hw_lock held.
> > > > + * If all the buffers required to form a job are available, append the
> > > > + * job descriptor to the job queue to be later queued to the HW.
> > > >   *
> > > >   * Returns 0 if a job has been successfully prepared, < 0 otherwise.
> > > >   */
> > > > -static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> > > > -			      struct pispbe_job_descriptor *job)
> > > > +static int pispbe_prepare_job(struct pispbe_dev *pispbe)
> > > >  {
> > > >  	struct pispbe_buffer *buf[PISPBE_NUM_NODES] = {};
> > > > +	struct pispbe_job_descriptor *job;
> > > > +	unsigned int streaming_map;
> > > >  	unsigned int config_index;
> > > >  	struct pispbe_node *node;
> > > > -	unsigned long flags;
> > > >
> > > > -	lockdep_assert_held(&pispbe->hw_lock);
> > > > +	scoped_guard(spinlock, &pispbe->hw_lock) {
> > >
> > > I think I've mis-communicated the locking requirements. This spinlock is
> > > taken in both non-IRQ contexts (here) and in mixed IRQ and non-IRQ
> > > contexts (pispbe_schedule(), called from both IRQ context in
> > > pispbe_isr() and non-IRQ context in pispbe_node_buffer_queue() and
> > > pispbe_node_start_streaming()).
> > >
> > > This means that the non-IRQ contexts should use spinlock_irq(), and the
> > > mixed contexts should use spinlock_irqsave().
> > >
> >
> > Yeah sorry, I admit I hadn't put much attention to this
> >
> > > > +		static const u32 mask = BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE);
> > > >
> > > > -	memset(job, 0, sizeof(struct pispbe_job_descriptor));
> > > > +		if ((pispbe->streaming_map & mask) != mask)
> > > > +			return -ENODEV;
> > > >
> > > > -	if (((BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE)) &
> > > > -		pispbe->streaming_map) !=
> > > > -			(BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE)))
> > > > -		return -ENODEV;
> > > > +		/*
> > > > +		 * Take a copy of streaming_map: nodes activated after this
> > > > +		 * point are ignored when preparing this job.
> > > > +		 */
> > > > +		streaming_map = pispbe->streaming_map;
> > > > +	}
> > > > +
> > > > +	job = kzalloc(sizeof(*job), GFP_KERNEL);
> > > > +	if (!job)
> > > > +		return -ENOMEM;
> > > >
> > > >  	node = &pispbe->node[CONFIG_NODE];
> > > > -	spin_lock_irqsave(&node->ready_lock, flags);
> > > >  	buf[CONFIG_NODE] = list_first_entry_or_null(&node->ready_queue,
> > > >  						    struct pispbe_buffer,
> > > >  						    ready_list);
> > > > -	if (buf[CONFIG_NODE]) {
> > > > -		list_del(&buf[CONFIG_NODE]->ready_list);
> > > > -		pispbe->queued_job.buf[CONFIG_NODE] = buf[CONFIG_NODE];
> > > > +	if (!buf[CONFIG_NODE]) {
> > > > +		kfree(job);
> > > > +		return -ENODEV;
> > > >  	}
> > > > -	spin_unlock_irqrestore(&node->ready_lock, flags);
> > > >
> > > > -	/* Exit early if no config buffer has been queued. */
> > > > -	if (!buf[CONFIG_NODE])
> > > > -		return -ENODEV;
> > > > +	list_del(&buf[CONFIG_NODE]->ready_list);
> > > > +	job->buffers[CONFIG_NODE] = buf[CONFIG_NODE];
> > > >
> > > >  	config_index = buf[CONFIG_NODE]->vb.vb2_buf.index;
> > > >  	job->config = &pispbe->config[config_index];
> > > > @@ -495,7 +503,7 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> > > >  			continue;
> > > >
> > > >  		buf[i] = NULL;
> > > > -		if (!(pispbe->streaming_map & BIT(i)))
> > > > +		if (!(streaming_map & BIT(i)))
> > > >  			continue;
> > > >
> > > >  		if ((!(rgb_en & PISP_BE_RGB_ENABLE_OUTPUT0) &&
> > > > @@ -522,25 +530,25 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> > > >  		node = &pispbe->node[i];
> > > >
> > > >  		/* Pull a buffer from each V4L2 queue to form the queued job */
> > > > -		spin_lock_irqsave(&node->ready_lock, flags);
> > > >  		buf[i] = list_first_entry_or_null(&node->ready_queue,
> > > >  						  struct pispbe_buffer,
> > > >  						  ready_list);
> > > >  		if (buf[i]) {
> > > >  			list_del(&buf[i]->ready_list);
> > > > -			pispbe->queued_job.buf[i] = buf[i];
> > > > +			job->buffers[i] = buf[i];
> > > >  		}
> > > > -		spin_unlock_irqrestore(&node->ready_lock, flags);
> > > >
> > > >  		if (!buf[i] && !ignore_buffers)
> > > >  			goto err_return_buffers;
> > > >  	}
> > > >
> > > > -	pispbe->queued_job.valid = true;
> > > > -
> > > >  	/* Convert buffers to DMA addresses for the hardware */
> > > >  	pispbe_xlate_addrs(pispbe, job, buf);
> > > >
> > > > +	spin_lock(&pispbe->hw_lock);
> > > > +	list_add_tail(&job->queue, &pispbe->job_queue);
> > > > +	spin_unlock(&pispbe->hw_lock);
> > > > +
> > > >  	return 0;
> > > >
> > > >  err_return_buffers:
> > > > @@ -551,33 +559,39 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> > > >  			continue;
> > > >
> > > >  		/* Return the buffer to the ready_list queue */
> > > > -		spin_lock_irqsave(&n->ready_lock, flags);
> > > >  		list_add(&buf[i]->ready_list, &n->ready_queue);
> > > > -		spin_unlock_irqrestore(&n->ready_lock, flags);
> > > >  	}
> > > >
> > > > -	memset(&pispbe->queued_job, 0, sizeof(pispbe->queued_job));
> > > > +	kfree(job);
> > > >
> > > >  	return -ENODEV;
> > > >  }
> > > >
> > > >  static void pispbe_schedule(struct pispbe_dev *pispbe, bool clear_hw_busy)
> > > >  {
> > > > -	struct pispbe_job_descriptor job;
> > > > -	unsigned long flags;
> > > > -	int ret;
> > > > +	struct pispbe_job_descriptor *job;
> > > >
> > > > -	spin_lock_irqsave(&pispbe->hw_lock, flags);
> > > > +	scoped_guard(spinlock, &pispbe->hw_lock) {
> > > > +		if (clear_hw_busy)
> > > > +			pispbe->hw_busy = false;
> > > > +
> > > > +		if (pispbe->hw_busy)
> > > > +			return;
> > > >
> > > > -	if (clear_hw_busy)
> > > > -		pispbe->hw_busy = false;
> > > > +		job = list_first_entry_or_null(&pispbe->job_queue,
> > > > +					       struct pispbe_job_descriptor,
> > > > +					       queue);
> > > > +		if (!job)
> > > > +			return;
> > > >
> > > > -	if (pispbe->hw_busy)
> > > > -		goto unlock_and_return;
> > > > +		list_del(&job->queue);
> > > >
> > > > -	ret = pispbe_prepare_job(pispbe, &job);
> > > > -	if (ret)
> > > > -		goto unlock_and_return;
> > > > +		for (unsigned int i = 0; i < PISPBE_NUM_NODES; i++)
> > > > +			pispbe->queued_job.buf[i] = job->buffers[i];
> > > > +		 pispbe->queued_job.valid = true;
> > > > +
> > > > +		pispbe->hw_busy = true;
> > > > +	}
> > > >
> > > >  	/*
> > > >  	 * We can kick the job off without the hw_lock, as this can
> > > > @@ -585,16 +599,8 @@ static void pispbe_schedule(struct pispbe_dev *pispbe, bool clear_hw_busy)
> > > >  	 * only when the following job has been queued and an interrupt
> > > >  	 * is rised.
> > > >  	 */
> > > > -	pispbe->hw_busy = true;
> > > > -	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> > > > -
> > > > -	pispbe_queue_job(pispbe, &job);
> > > > -
> > > > -	return;
> > > > -
> > > > -unlock_and_return:
> > > > -	/* No job has been queued, just release the lock and return. */
> > > > -	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> > > > +	pispbe_queue_job(pispbe, job);
> > > > +	kfree(job);
> > > >  }
> > > >
> > > >  static void pispbe_isr_jobdone(struct pispbe_dev *pispbe,
> > > > @@ -846,18 +852,16 @@ static void pispbe_node_buffer_queue(struct vb2_buffer *buf)
> > > >  		container_of(vbuf, struct pispbe_buffer, vb);
> > > >  	struct pispbe_node *node = vb2_get_drv_priv(buf->vb2_queue);
> > > >  	struct pispbe_dev *pispbe = node->pispbe;
> > > > -	unsigned long flags;
> > > >
> > > >  	dev_dbg(pispbe->dev, "%s: for node %s\n", __func__, NODE_NAME(node));
> > > > -	spin_lock_irqsave(&node->ready_lock, flags);
> > > >  	list_add_tail(&buffer->ready_list, &node->ready_queue);
> > > > -	spin_unlock_irqrestore(&node->ready_lock, flags);
> > > >
> > > >  	/*
> > > >  	 * Every time we add a buffer, check if there's now some work for the hw
> > > >  	 * to do.
> > > >  	 */
> > > > -	pispbe_schedule(pispbe, false);
> > > > +	if (!pispbe_prepare_job(pispbe))
> > > > +		pispbe_schedule(pispbe, false);
> > > >  }
> > > >
> > > >  static int pispbe_node_start_streaming(struct vb2_queue *q, unsigned int count)
> > > > @@ -883,7 +887,8 @@ static int pispbe_node_start_streaming(struct vb2_queue *q, unsigned int count)
> > > >  		node->pispbe->streaming_map);
> > > >
> > > >  	/* Maybe we're ready to run. */
> > > > -	pispbe_schedule(pispbe, false);
> > > > +	if (!pispbe_prepare_job(pispbe))
> > > > +		pispbe_schedule(pispbe, false);
> > > >
> > > >  	return 0;
> > > >
> > > > @@ -917,9 +922,6 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
> > > >  	dev_dbg(pispbe->dev, "%s: for node %s\n", __func__, NODE_NAME(node));
> > > >  	spin_lock_irqsave(&pispbe->hw_lock, flags);
> > >
> > > Is the lock needed here ? And in the err_return_buffers error path in
> > > pispbe_node_start_streaming() ? Both seem to touch the ready_queue only,
> > > which isn't protected by the hw_lock.
> >
> > No the lock is not needed, and as this is not irq context I should
> > switch both stop_streaming() and start_streaming() to use
> > spink_lock_irq()
> >
> > > >  	do {
> > > > -		unsigned long flags1;
> > > > -
> > > > -		spin_lock_irqsave(&node->ready_lock, flags1);
> > > >  		buf = list_first_entry_or_null(&node->ready_queue,
> > > >  					       struct pispbe_buffer,
> > > >  					       ready_list);
> > > > @@ -927,7 +929,6 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
> > > >  			list_del(&buf->ready_list);
> > > >  			vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
> > > >  		}
> > > > -		spin_unlock_irqrestore(&node->ready_lock, flags1);
> > > >  	} while (buf);
> > > >  	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> > > >
> > > > @@ -935,6 +936,16 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
> > > >
> > > >  	spin_lock_irqsave(&pispbe->hw_lock, flags);
> > > >  	pispbe->streaming_map &= ~BIT(node->id);
> > > > +
> > > > +	/* Release all jobs once all nodes have stopped streaming. */
> > > > +	if (pispbe->streaming_map == 0) {
> > > > +		struct pispbe_job_descriptor *job, *temp;
> > > > +
> > > > +		list_for_each_entry_safe(job, temp, &pispbe->job_queue, queue) {
> > > > +			list_del(&job->queue);
> > > > +			kfree(job);
> > > > +		}
> > >
> > > I think this can be done outside of the lock.
> > >
> >
> > Does it ? The job queue is accessed by the irq handler. As we
> > stop the interface -after- having cleared the job queue here, I would
> > keep this sequence inside the lock to be honest.
>
> Ah yes you right. I'm not sure what I missed.
>
> What you can do here, though, is to splice the job_queue to a local list
> with the lock, and then iterate over the local list and free the jobs
> without the lock.
>

Do you expect this to be such a critical path that this is reequired ?
True, the lock is contended with the irq handler, but I don't expect
the job queue to be that long. Do you ?

> > > > +	}
> > > >  	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> > > >
> > > >  	pm_runtime_mark_last_busy(pispbe->dev);
> > > > @@ -1393,7 +1404,6 @@ static int pispbe_init_node(struct pispbe_dev *pispbe, unsigned int id)
> > > >  	mutex_init(&node->node_lock);
> > > >  	mutex_init(&node->queue_lock);
> > > >  	INIT_LIST_HEAD(&node->ready_queue);
> > > > -	spin_lock_init(&node->ready_lock);
> > > >
> > > >  	node->format.type = node->buf_type;
> > > >  	pispbe_node_def_fmt(node);
> > > > @@ -1677,6 +1687,8 @@ static int pispbe_probe(struct platform_device *pdev)
> > > >  	if (!pispbe)
> > > >  		return -ENOMEM;
> > > >
> > > > +	INIT_LIST_HEAD(&pispbe->job_queue);
> > > > +
> > > >  	dev_set_drvdata(&pdev->dev, pispbe);
> > > >  	pispbe->dev = &pdev->dev;
> > > >  	platform_set_drvdata(pdev, pispbe);
>
> --
> Regards,
>
> Laurent Pinchart

Re: [PATCH v4 3/4] media: pisp-be: Split jobs creation and scheduling

[Laurent Pinchart]

On Wed, Sep 04, 2024 at 10:35:18AM +0200, Jacopo Mondi wrote:
> Hi Laurent
> 
> On Wed, Sep 04, 2024 at 10:53:02AM GMT, Laurent Pinchart wrote:
> > On Wed, Sep 04, 2024 at 09:21:45AM +0200, Jacopo Mondi wrote:
> > > Hi Laurent
> > >
> > > On Tue, Sep 03, 2024 at 03:19:36PM GMT, Laurent Pinchart wrote:
> > > > Hi Jacopo,
> > > >
> > > > Thank you for the patch.
> > > >
> > > > I just noticed the subject line writes "pisp-be" while all other patches
> > > > in the series use "pisp_be".
> > > >
> > > > On Mon, Sep 02, 2024 at 01:24:05PM +0200, Jacopo Mondi wrote:
> > > > > Currently the 'pispbe_schedule()' function does two things:
> > > > >
> > > > > 1) Tries to assemble a job by inspecting all the video node queues
> > > > >    to make sure all the required buffers are available
> > > > > 2) Submit the job to the hardware
> > > > >
> > > > > The pispbe_schedule() function is called at:
> > > > >
> > > > > - video device start_streaming() time
> > > > > - video device qbuf() time
> > > > > - irq handler
> > > > >
> > > > > As assembling a job requires inspecting all queues, it is a rather
> > > > > time consuming operation which is better not run in IRQ context.
> > > > >
> > > > > To avoid the executing the time consuming job creation in interrupt
> > > > > context split the job creation and job scheduling in two distinct
> > > > > operations. When a well-formed job is created, append it to the
> > > > > newly introduced 'pispbe->job_queue' where it will be dequeued from
> > > > > by the scheduling routine.
> > > > >
> > > > > At start_streaming() and qbuf() time immediately try to schedule a job
> > > > > if one has been created as the irq handler routing is only called when
> > > > > a job has completed, and we can't solely rely on it for scheduling new
> > > > > jobs.
> > > > >
> > > > > As now the per-node 'ready_queue' buffer list is only accessed in vb2
> > > > > ops callbacks, protected by a mutex, it is not necessary to guard it
> > > > > with a dedicated spinlock so drop it.
> > > > >
> > > > > Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
> > > > > ---
> > > > >  .../platform/raspberrypi/pisp_be/pisp_be.c    | 134 ++++++++++--------
> > > > >  1 file changed, 73 insertions(+), 61 deletions(-)
> > > > >
> > > > > diff --git a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> > > > > index 41fd68b7757b..d614f53f0f68 100644
> > > > > --- a/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> > > > > +++ b/drivers/media/platform/raspberrypi/pisp_be/pisp_be.c
> > > > > @@ -161,8 +161,6 @@ struct pispbe_node {
> > > > >  	struct mutex node_lock;
> > > > >  	/* vb2_queue lock */
> > > > >  	struct mutex queue_lock;
> > > > > -	/* Protect pispbe_node->ready_queue and pispbe_buffer->ready_list */
> > > > > -	spinlock_t ready_lock;
> > > > >  	struct list_head ready_queue;
> > > > >  	struct vb2_queue queue;
> > > > >  	struct v4l2_format format;
> > > > > @@ -190,6 +188,8 @@ struct pispbe_hw_enables {
> > > > >
> > > > >  /* Records a job configuration and memory addresses. */
> > > > >  struct pispbe_job_descriptor {
> > > > > +	struct list_head queue;
> > > > > +	struct pispbe_buffer *buffers[PISPBE_NUM_NODES];
> > > > >  	dma_addr_t hw_dma_addrs[N_HW_ADDRESSES];
> > > > >  	struct pisp_be_tiles_config *config;
> > > > >  	struct pispbe_hw_enables hw_enables;
> > > > > @@ -215,8 +215,10 @@ struct pispbe_dev {
> > > > >  	unsigned int sequence;
> > > > >  	u32 streaming_map;
> > > > >  	struct pispbe_job queued_job, running_job;
> > > > > -	spinlock_t hw_lock; /* protects "hw_busy" flag and streaming_map */
> > > > > +	/* protects "hw_busy" flag, streaming_map and job_queue */
> > > > > +	spinlock_t hw_lock;
> > > > >  	bool hw_busy; /* non-zero if a job is queued or is being started */
> > > > > +	struct list_head job_queue;
> > > > >  	int irq;
> > > > >  	u32 hw_version;
> > > > >  	u8 done, started;
> > > > > @@ -440,41 +442,47 @@ static void pispbe_xlate_addrs(struct pispbe_dev *pispbe,
> > > > >   * For Output0, Output1, Tdn and Stitch, a buffer only needs to be
> > > > >   * available if the blocks are enabled in the config.
> > > > >   *
> > > > > - * Needs to be called with hw_lock held.
> > > > > + * If all the buffers required to form a job are available, append the
> > > > > + * job descriptor to the job queue to be later queued to the HW.
> > > > >   *
> > > > >   * Returns 0 if a job has been successfully prepared, < 0 otherwise.
> > > > >   */
> > > > > -static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> > > > > -			      struct pispbe_job_descriptor *job)
> > > > > +static int pispbe_prepare_job(struct pispbe_dev *pispbe)
> > > > >  {
> > > > >  	struct pispbe_buffer *buf[PISPBE_NUM_NODES] = {};
> > > > > +	struct pispbe_job_descriptor *job;
> > > > > +	unsigned int streaming_map;
> > > > >  	unsigned int config_index;
> > > > >  	struct pispbe_node *node;
> > > > > -	unsigned long flags;
> > > > >
> > > > > -	lockdep_assert_held(&pispbe->hw_lock);
> > > > > +	scoped_guard(spinlock, &pispbe->hw_lock) {
> > > >
> > > > I think I've mis-communicated the locking requirements. This spinlock is
> > > > taken in both non-IRQ contexts (here) and in mixed IRQ and non-IRQ
> > > > contexts (pispbe_schedule(), called from both IRQ context in
> > > > pispbe_isr() and non-IRQ context in pispbe_node_buffer_queue() and
> > > > pispbe_node_start_streaming()).
> > > >
> > > > This means that the non-IRQ contexts should use spinlock_irq(), and the
> > > > mixed contexts should use spinlock_irqsave().
> > > >
> > >
> > > Yeah sorry, I admit I hadn't put much attention to this
> > >
> > > > > +		static const u32 mask = BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE);
> > > > >
> > > > > -	memset(job, 0, sizeof(struct pispbe_job_descriptor));
> > > > > +		if ((pispbe->streaming_map & mask) != mask)
> > > > > +			return -ENODEV;
> > > > >
> > > > > -	if (((BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE)) &
> > > > > -		pispbe->streaming_map) !=
> > > > > -			(BIT(CONFIG_NODE) | BIT(MAIN_INPUT_NODE)))
> > > > > -		return -ENODEV;
> > > > > +		/*
> > > > > +		 * Take a copy of streaming_map: nodes activated after this
> > > > > +		 * point are ignored when preparing this job.
> > > > > +		 */
> > > > > +		streaming_map = pispbe->streaming_map;
> > > > > +	}
> > > > > +
> > > > > +	job = kzalloc(sizeof(*job), GFP_KERNEL);
> > > > > +	if (!job)
> > > > > +		return -ENOMEM;
> > > > >
> > > > >  	node = &pispbe->node[CONFIG_NODE];
> > > > > -	spin_lock_irqsave(&node->ready_lock, flags);
> > > > >  	buf[CONFIG_NODE] = list_first_entry_or_null(&node->ready_queue,
> > > > >  						    struct pispbe_buffer,
> > > > >  						    ready_list);
> > > > > -	if (buf[CONFIG_NODE]) {
> > > > > -		list_del(&buf[CONFIG_NODE]->ready_list);
> > > > > -		pispbe->queued_job.buf[CONFIG_NODE] = buf[CONFIG_NODE];
> > > > > +	if (!buf[CONFIG_NODE]) {
> > > > > +		kfree(job);
> > > > > +		return -ENODEV;
> > > > >  	}
> > > > > -	spin_unlock_irqrestore(&node->ready_lock, flags);
> > > > >
> > > > > -	/* Exit early if no config buffer has been queued. */
> > > > > -	if (!buf[CONFIG_NODE])
> > > > > -		return -ENODEV;
> > > > > +	list_del(&buf[CONFIG_NODE]->ready_list);
> > > > > +	job->buffers[CONFIG_NODE] = buf[CONFIG_NODE];
> > > > >
> > > > >  	config_index = buf[CONFIG_NODE]->vb.vb2_buf.index;
> > > > >  	job->config = &pispbe->config[config_index];
> > > > > @@ -495,7 +503,7 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> > > > >  			continue;
> > > > >
> > > > >  		buf[i] = NULL;
> > > > > -		if (!(pispbe->streaming_map & BIT(i)))
> > > > > +		if (!(streaming_map & BIT(i)))
> > > > >  			continue;
> > > > >
> > > > >  		if ((!(rgb_en & PISP_BE_RGB_ENABLE_OUTPUT0) &&
> > > > > @@ -522,25 +530,25 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> > > > >  		node = &pispbe->node[i];
> > > > >
> > > > >  		/* Pull a buffer from each V4L2 queue to form the queued job */
> > > > > -		spin_lock_irqsave(&node->ready_lock, flags);
> > > > >  		buf[i] = list_first_entry_or_null(&node->ready_queue,
> > > > >  						  struct pispbe_buffer,
> > > > >  						  ready_list);
> > > > >  		if (buf[i]) {
> > > > >  			list_del(&buf[i]->ready_list);
> > > > > -			pispbe->queued_job.buf[i] = buf[i];
> > > > > +			job->buffers[i] = buf[i];
> > > > >  		}
> > > > > -		spin_unlock_irqrestore(&node->ready_lock, flags);
> > > > >
> > > > >  		if (!buf[i] && !ignore_buffers)
> > > > >  			goto err_return_buffers;
> > > > >  	}
> > > > >
> > > > > -	pispbe->queued_job.valid = true;
> > > > > -
> > > > >  	/* Convert buffers to DMA addresses for the hardware */
> > > > >  	pispbe_xlate_addrs(pispbe, job, buf);
> > > > >
> > > > > +	spin_lock(&pispbe->hw_lock);
> > > > > +	list_add_tail(&job->queue, &pispbe->job_queue);
> > > > > +	spin_unlock(&pispbe->hw_lock);
> > > > > +
> > > > >  	return 0;
> > > > >
> > > > >  err_return_buffers:
> > > > > @@ -551,33 +559,39 @@ static int pispbe_prepare_job(struct pispbe_dev *pispbe,
> > > > >  			continue;
> > > > >
> > > > >  		/* Return the buffer to the ready_list queue */
> > > > > -		spin_lock_irqsave(&n->ready_lock, flags);
> > > > >  		list_add(&buf[i]->ready_list, &n->ready_queue);
> > > > > -		spin_unlock_irqrestore(&n->ready_lock, flags);
> > > > >  	}
> > > > >
> > > > > -	memset(&pispbe->queued_job, 0, sizeof(pispbe->queued_job));
> > > > > +	kfree(job);
> > > > >
> > > > >  	return -ENODEV;
> > > > >  }
> > > > >
> > > > >  static void pispbe_schedule(struct pispbe_dev *pispbe, bool clear_hw_busy)
> > > > >  {
> > > > > -	struct pispbe_job_descriptor job;
> > > > > -	unsigned long flags;
> > > > > -	int ret;
> > > > > +	struct pispbe_job_descriptor *job;
> > > > >
> > > > > -	spin_lock_irqsave(&pispbe->hw_lock, flags);
> > > > > +	scoped_guard(spinlock, &pispbe->hw_lock) {
> > > > > +		if (clear_hw_busy)
> > > > > +			pispbe->hw_busy = false;
> > > > > +
> > > > > +		if (pispbe->hw_busy)
> > > > > +			return;
> > > > >
> > > > > -	if (clear_hw_busy)
> > > > > -		pispbe->hw_busy = false;
> > > > > +		job = list_first_entry_or_null(&pispbe->job_queue,
> > > > > +					       struct pispbe_job_descriptor,
> > > > > +					       queue);
> > > > > +		if (!job)
> > > > > +			return;
> > > > >
> > > > > -	if (pispbe->hw_busy)
> > > > > -		goto unlock_and_return;
> > > > > +		list_del(&job->queue);
> > > > >
> > > > > -	ret = pispbe_prepare_job(pispbe, &job);
> > > > > -	if (ret)
> > > > > -		goto unlock_and_return;
> > > > > +		for (unsigned int i = 0; i < PISPBE_NUM_NODES; i++)
> > > > > +			pispbe->queued_job.buf[i] = job->buffers[i];
> > > > > +		 pispbe->queued_job.valid = true;
> > > > > +
> > > > > +		pispbe->hw_busy = true;
> > > > > +	}
> > > > >
> > > > >  	/*
> > > > >  	 * We can kick the job off without the hw_lock, as this can
> > > > > @@ -585,16 +599,8 @@ static void pispbe_schedule(struct pispbe_dev *pispbe, bool clear_hw_busy)
> > > > >  	 * only when the following job has been queued and an interrupt
> > > > >  	 * is rised.
> > > > >  	 */
> > > > > -	pispbe->hw_busy = true;
> > > > > -	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> > > > > -
> > > > > -	pispbe_queue_job(pispbe, &job);
> > > > > -
> > > > > -	return;
> > > > > -
> > > > > -unlock_and_return:
> > > > > -	/* No job has been queued, just release the lock and return. */
> > > > > -	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> > > > > +	pispbe_queue_job(pispbe, job);
> > > > > +	kfree(job);
> > > > >  }
> > > > >
> > > > >  static void pispbe_isr_jobdone(struct pispbe_dev *pispbe,
> > > > > @@ -846,18 +852,16 @@ static void pispbe_node_buffer_queue(struct vb2_buffer *buf)
> > > > >  		container_of(vbuf, struct pispbe_buffer, vb);
> > > > >  	struct pispbe_node *node = vb2_get_drv_priv(buf->vb2_queue);
> > > > >  	struct pispbe_dev *pispbe = node->pispbe;
> > > > > -	unsigned long flags;
> > > > >
> > > > >  	dev_dbg(pispbe->dev, "%s: for node %s\n", __func__, NODE_NAME(node));
> > > > > -	spin_lock_irqsave(&node->ready_lock, flags);
> > > > >  	list_add_tail(&buffer->ready_list, &node->ready_queue);
> > > > > -	spin_unlock_irqrestore(&node->ready_lock, flags);
> > > > >
> > > > >  	/*
> > > > >  	 * Every time we add a buffer, check if there's now some work for the hw
> > > > >  	 * to do.
> > > > >  	 */
> > > > > -	pispbe_schedule(pispbe, false);
> > > > > +	if (!pispbe_prepare_job(pispbe))
> > > > > +		pispbe_schedule(pispbe, false);
> > > > >  }
> > > > >
> > > > >  static int pispbe_node_start_streaming(struct vb2_queue *q, unsigned int count)
> > > > > @@ -883,7 +887,8 @@ static int pispbe_node_start_streaming(struct vb2_queue *q, unsigned int count)
> > > > >  		node->pispbe->streaming_map);
> > > > >
> > > > >  	/* Maybe we're ready to run. */
> > > > > -	pispbe_schedule(pispbe, false);
> > > > > +	if (!pispbe_prepare_job(pispbe))
> > > > > +		pispbe_schedule(pispbe, false);
> > > > >
> > > > >  	return 0;
> > > > >
> > > > > @@ -917,9 +922,6 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
> > > > >  	dev_dbg(pispbe->dev, "%s: for node %s\n", __func__, NODE_NAME(node));
> > > > >  	spin_lock_irqsave(&pispbe->hw_lock, flags);
> > > >
> > > > Is the lock needed here ? And in the err_return_buffers error path in
> > > > pispbe_node_start_streaming() ? Both seem to touch the ready_queue only,
> > > > which isn't protected by the hw_lock.
> > >
> > > No the lock is not needed, and as this is not irq context I should
> > > switch both stop_streaming() and start_streaming() to use
> > > spink_lock_irq()
> > >
> > > > >  	do {
> > > > > -		unsigned long flags1;
> > > > > -
> > > > > -		spin_lock_irqsave(&node->ready_lock, flags1);
> > > > >  		buf = list_first_entry_or_null(&node->ready_queue,
> > > > >  					       struct pispbe_buffer,
> > > > >  					       ready_list);
> > > > > @@ -927,7 +929,6 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
> > > > >  			list_del(&buf->ready_list);
> > > > >  			vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
> > > > >  		}
> > > > > -		spin_unlock_irqrestore(&node->ready_lock, flags1);
> > > > >  	} while (buf);
> > > > >  	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> > > > >
> > > > > @@ -935,6 +936,16 @@ static void pispbe_node_stop_streaming(struct vb2_queue *q)
> > > > >
> > > > >  	spin_lock_irqsave(&pispbe->hw_lock, flags);
> > > > >  	pispbe->streaming_map &= ~BIT(node->id);
> > > > > +
> > > > > +	/* Release all jobs once all nodes have stopped streaming. */
> > > > > +	if (pispbe->streaming_map == 0) {
> > > > > +		struct pispbe_job_descriptor *job, *temp;
> > > > > +
> > > > > +		list_for_each_entry_safe(job, temp, &pispbe->job_queue, queue) {
> > > > > +			list_del(&job->queue);
> > > > > +			kfree(job);
> > > > > +		}
> > > >
> > > > I think this can be done outside of the lock.
> > > >
> > >
> > > Does it ? The job queue is accessed by the irq handler. As we
> > > stop the interface -after- having cleared the job queue here, I would
> > > keep this sequence inside the lock to be honest.
> >
> > Ah yes you right. I'm not sure what I missed.
> >
> > What you can do here, though, is to splice the job_queue to a local list
> > with the lock, and then iterate over the local list and free the jobs
> > without the lock.
> 
> Do you expect this to be such a critical path that this is reequired ?
> True, the lock is contended with the irq handler, but I don't expect
> the job queue to be that long. Do you ?

No, but kfree() is not necessarily a very cheap operation. I think it's
worth splicing the list as it's easy.

> > > > > +	}
> > > > >  	spin_unlock_irqrestore(&pispbe->hw_lock, flags);
> > > > >
> > > > >  	pm_runtime_mark_last_busy(pispbe->dev);
> > > > > @@ -1393,7 +1404,6 @@ static int pispbe_init_node(struct pispbe_dev *pispbe, unsigned int id)
> > > > >  	mutex_init(&node->node_lock);
> > > > >  	mutex_init(&node->queue_lock);
> > > > >  	INIT_LIST_HEAD(&node->ready_queue);
> > > > > -	spin_lock_init(&node->ready_lock);
> > > > >
> > > > >  	node->format.type = node->buf_type;
> > > > >  	pispbe_node_def_fmt(node);
> > > > > @@ -1677,6 +1687,8 @@ static int pispbe_probe(struct platform_device *pdev)
> > > > >  	if (!pispbe)
> > > > >  		return -ENOMEM;
> > > > >
> > > > > +	INIT_LIST_HEAD(&pispbe->job_queue);
> > > > > +
> > > > >  	dev_set_drvdata(&pdev->dev, pispbe);
> > > > >  	pispbe->dev = &pdev->dev;
> > > > >  	platform_set_drvdata(pdev, pispbe);

-- 
Regards,

Laurent Pinchart