[PATCH v9 3/3] dma-buf/sw_sync: Add fence deadline support

Rob Clark
2023-08-23T21:57:10Z

This consists of simply storing the most recent deadline, and adding an
ioctl to retrieve the deadline. This can be used in conjunction with
the SET_DEADLINE ioctl on a fence fd for testing. Ie. create various
sw_sync fences, merge them into a fence-array, set deadline on the
fence-array and confirm that it is propagated properly to each fence.

v2: Switch UABI to express deadline as u64
v3: More verbose UAPI docs, show how to convert from timespec
v4: Better comments, track the soonest deadline, as a normal fence
implementation would, return an error if no deadline set.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Christian König <christian.koenig@amd.com>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
---
drivers/dma-buf/sw_sync.c | 82 ++++++++++++++++++++++++++++++++++++
drivers/dma-buf/sync_debug.h | 2 +
2 files changed, 84 insertions(+)

diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c
index f0a35277fd84..c353029789cf 100644
--- a/drivers/dma-buf/sw_sync.c
+++ b/drivers/dma-buf/sw_sync.c
@@ -52,12 +52,33 @@ struct sw_sync_create_fence_data {
__s32 fence; /* fd of new fence */
};

+/**
+ * struct sw_sync_get_deadline - get the deadline hint of a sw_sync fence
+ * @deadline_ns: absolute time of the deadline
+ * @pad: must be zero
+ * @fence_fd: the sw_sync fence fd (in)
+ *
+ * Return the earliest deadline set on the fence. The timebase for the
+ * deadline is CLOCK_MONOTONIC (same as vblank). If there is no deadline
+ * set on the fence, this ioctl will return -ENOENT.
+ */
+struct sw_sync_get_deadline {
+ __u64 deadline_ns;
+ __u32 pad;
+ __s32 fence_fd;
+};
+
#define SW_SYNC_IOC_MAGIC 'W'

#define SW_SYNC_IOC_CREATE_FENCE _IOWR(SW_SYNC_IOC_MAGIC, 0,\
struct sw_sync_create_fence_data)

#define SW_SYNC_IOC_INC _IOW(SW_SYNC_IOC_MAGIC, 1, __u32)
+#define SW_SYNC_GET_DEADLINE _IOWR(SW_SYNC_IOC_MAGIC, 2, \
+ struct sw_sync_get_deadline)
+
+
+#define SW_SYNC_HAS_DEADLINE_BIT DMA_FENCE_FLAG_USER_BITS

static const struct dma_fence_ops timeline_fence_ops;

@@ -171,6 +192,22 @@ static void timeline_fence_timeline_value_str(struct dma_fence *fence,
snprintf(str, size, "%d", parent->value);
}

+static void timeline_fence_set_deadline(struct dma_fence *fence, ktime_t deadline)
+{
+ struct sync_pt *pt = dma_fence_to_sync_pt(fence);
+ unsigned long flags;
+
+ spin_lock_irqsave(fence->lock, flags);
+ if (test_bit(SW_SYNC_HAS_DEADLINE_BIT, &fence->flags)) {
+ if (ktime_before(deadline, pt->deadline))
+ pt->deadline = deadline;
+ } else {
+ pt->deadline = deadline;
+ __set_bit(SW_SYNC_HAS_DEADLINE_BIT, &fence->flags);
+ }
+ spin_unlock_irqrestore(fence->lock, flags);
+}
+
static const struct dma_fence_ops timeline_fence_ops = {
.get_driver_name = timeline_fence_get_driver_name,
.get_timeline_name = timeline_fence_get_timeline_name,
@@ -179,6 +216,7 @@ static const struct dma_fence_ops timeline_fence_ops = {
.release = timeline_fence_release,
.fence_value_str = timeline_fence_value_str,
.timeline_value_str = timeline_fence_timeline_value_str,
+ .set_deadline = timeline_fence_set_deadline,
};

/**
@@ -387,6 +425,47 @@ static long sw_sync_ioctl_inc(struct sync_timeline *obj, unsigned long arg)
return 0;
}

+static int sw_sync_ioctl_get_deadline(struct sync_timeline *obj, unsigned long arg)
+{
+ struct sw_sync_get_deadline data;
+ struct dma_fence *fence;
+ unsigned long flags;
+ struct sync_pt *pt;
+ int ret = 0;
+
+ if (copy_from_user(&data, (void __user *)arg, sizeof(data)))
+ return -EFAULT;
+
+ if (data.deadline_ns || data.pad)
+ return -EINVAL;
+
+ fence = sync_file_get_fence(data.fence_fd);
+ if (!fence)
+ return -EINVAL;
+
+ pt = dma_fence_to_sync_pt(fence);
+ if (!pt)
+ return -EINVAL;
+
+ spin_lock_irqsave(fence->lock, flags);
+ if (test_bit(SW_SYNC_HAS_DEADLINE_BIT, &fence->flags)) {
+ data.deadline_ns = ktime_to_ns(pt->deadline);
+ } else {
+ ret = -ENOENT;
+ }
+ spin_unlock_irqrestore(fence->lock, flags);
+
+ dma_fence_put(fence);
+
+ if (ret)
+ return ret;
+
+ if (copy_to_user((void __user *)arg, &data, sizeof(data)))
+ return -EFAULT;
+
+ return 0;
+}
+
static long sw_sync_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
@@ -399,6 +478,9 @@ static long sw_sync_ioctl(struct file *file, unsigned int cmd,
case SW_SYNC_IOC_INC:
return sw_sync_ioctl_inc(obj, arg);

+ case SW_SYNC_GET_DEADLINE:
+ return sw_sync_ioctl_get_deadline(obj, arg);
+
default:
return -ENOTTY;
}
diff --git a/drivers/dma-buf/sync_debug.h b/drivers/dma-buf/sync_debug.h
index 6176e52ba2d7..a1bdd62efccd 100644
--- a/drivers/dma-buf/sync_debug.h
+++ b/drivers/dma-buf/sync_debug.h
@@ -55,11 +55,13 @@ static inline struct sync_timeline *dma_fence_parent(struct dma_fence *fence)
* @base: base fence object
* @link: link on the sync timeline's list
* @node: node in the sync timeline's tree
+ * @deadline: the earliest fence deadline hint
*/
struct sync_pt {
struct dma_fence base;
struct list_head link;
struct rb_node node;
+ ktime_t deadline;
};

extern const struct file_operations sw_sync_debugfs_fops;
--
2.41.0