FAILED: patch "[PATCH] media: microchip-isc: do not touch WB registers when not streaming" failed to apply to 5.15-stable tree

FAILED: patch "[PATCH] media: microchip-isc: do not touch WB registers when not streaming" failed to apply to 5.15-stable tree

[Sasha Levin]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x d8983c47d4d95eb1ed889dbb7516d3738fa854d8
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107055759-failed-5.15-d8983c47d4d9@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From d8983c47d4d95eb1ed889dbb7516d3738fa854d8 Mon Sep 17 00:00:00 2001
From: Balakrishnan Sambath <balakrishnan.s@microchip.com>
Date: Mon, 17 Aug 2026 12:22:02 +0530
Subject: [PATCH] media: microchip-isc: do not touch WB registers when not
 streaming

isc_s_awb_ctrl() called isc_update_awb_ctrls() unconditionally, writing
the white balance registers even when the device is runtime suspended;
on many ARM platforms accessing the unclocked registers is an external
abort. The write was also done without awb_lock, racing isc_awb_work(),
which holds it so the DMA done IRQ cannot latch a half-updated pipeline.

Write the registers only while streaming and not stopping, under
awb_lock, and update the profile there. The isc->stop check covers the
window where isc_stop_streaming() has gated the clocks but vb2 still
reports streaming. Otherwise the new values stay cached and
isc_configure() programs them at the next stream start.

Fixes: 4e52889f48fe ("media: atmel: atmel-isc-base: expose white balance as v4l2 controls")
Cc: stable@vger.kernel.org
Reviewed-by: Eugen Hristev <ehristev@kernel.org>
Signed-off-by: Balakrishnan Sambath <balakrishnan.s@microchip.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
---
 .../platform/microchip/microchip-isc-base.c   | 20 +++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/media/platform/microchip/microchip-isc-base.c b/drivers/media/platform/microchip/microchip-isc-base.c
index 0f486dd5bd82c..cf4611443fd13 100644
--- a/drivers/media/platform/microchip/microchip-isc-base.c
+++ b/drivers/media/platform/microchip/microchip-isc-base.c
@@ -1511,20 +1511,24 @@ static int isc_s_awb_ctrl(struct v4l2_ctrl *ctrl)
 		if (ctrl->cluster[ISC_CTRL_GB_OFF]->is_new)
 			ctrls->offset[ISC_HIS_CFG_MODE_GB] = isc->gb_off_ctrl->val;
 
-		isc_update_awb_ctrls(isc);
-
 		mutex_lock(&isc->awb_mutex);
-		if (vb2_is_streaming(&isc->vb2_vidq)) {
+		if (vb2_is_streaming(&isc->vb2_vidq) && !isc->stop) {
+			unsigned long flags;
+
 			/*
-			 * If we are streaming, we can update profile to
-			 * have the new settings in place.
+			 * awb_lock keeps the DMA done IRQ from latching a
+			 * partially written WB pipeline.
 			 */
+			spin_lock_irqsave(&isc->awb_lock, flags);
+			isc_update_awb_ctrls(isc);
+			spin_unlock_irqrestore(&isc->awb_lock, flags);
+
 			isc_update_profile(isc);
 		} else {
 			/*
-			 * The auto cluster will activate automatically this
-			 * control. This has to be deactivated when not
-			 * streaming.
+			 * Not streaming: keep the cached values for the next
+			 * stream start and deactivate the cluster-activated
+			 * do_white_balance button.
 			 */
 			v4l2_ctrl_activate(isc->do_wb_ctrl, false);
 		}
-- 
2.53.0

[PATCH 5.15.y 1/3] media: atmel: atmel-isc: remove redundant comments

[Sasha Levin]

From: Eugen Hristev <eugen.hristev@microchip.com>

[ Upstream commit 1f0c113cc7abb435e531f5777efe2ca757e1361b ]

Remove duplicate comments which are already in place before the struct
definition.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Stable-dep-of: d8983c47d4d9 ("media: microchip-isc: do not touch WB registers when not streaming")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/media/platform/atmel/atmel-isc.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/media/platform/atmel/atmel-isc.h b/drivers/media/platform/atmel/atmel-isc.h
index 2bfcb135ef13b..b0211100a5f23 100644
--- a/drivers/media/platform/atmel/atmel-isc.h
+++ b/drivers/media/platform/atmel/atmel-isc.h
@@ -261,7 +261,7 @@ struct isc_device {
 	struct video_device	video_dev;
 
 	struct vb2_queue	vb2_vidq;
-	spinlock_t		dma_queue_lock; /* serialize access to dma queue */
+	spinlock_t		dma_queue_lock;
 	struct list_head	dma_queue;
 	struct isc_buffer	*cur_frm;
 	unsigned int		sequence;
@@ -278,8 +278,8 @@ struct isc_device {
 	struct isc_ctrls	ctrls;
 	struct work_struct	awb_work;
 
-	struct mutex		lock; /* serialize access to file operations */
-	spinlock_t		awb_lock; /* serialize access to DMA buffers from awb work queue */
+	struct mutex		lock;
+	spinlock_t		awb_lock;
 
 	struct regmap_field	*pipeline[ISC_PIPE_LINE_NODE_NUM];
 
-- 
2.53.0

[PATCH 5.15.y 2/3] media: atmel: atmel-isc-base: use mutex to lock awb workq from streaming

[Sasha Levin]

From: Eugen Hristev <eugen.hristev@microchip.com>

[ Upstream commit 314c96e5203de1bac744e8536ef20b195f460674 ]

The AWB workqueue runs in a kernel thread and needs to be synchronized
w.r.t. the streaming status.
It is possible that streaming is stopped while the AWB workq is running.
In this case it is likely that the check for vb2_start_streaming_called is
done at one point in time, but the AWB computations are done later,
including a call to isc_update_profile, which requires streaming to be
started.
Thus , isc_update_profile will fail if during this operation sequence the
streaming was stopped.
To solve this issue, a mutex is added, that will serialize the awb work and
streaming stopping, with the mention that either streaming is stopped
completely including termination of the last frame is done, and after that
the AWB work can check stream status and stop; either first AWB work is
completed and after that the streaming can stop correctly.
The awb spin lock cannot be used since this spinlock is taken in the same
context and using it in the stop streaming will result in a recursion BUG.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Stable-dep-of: d8983c47d4d9 ("media: microchip-isc: do not touch WB registers when not streaming")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/media/platform/atmel/atmel-isc-base.c | 30 ++++++++++++++++---
 drivers/media/platform/atmel/atmel-isc.h      |  2 ++
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/drivers/media/platform/atmel/atmel-isc-base.c b/drivers/media/platform/atmel/atmel-isc-base.c
index eeaf91d80acd7..565719fda13c3 100644
--- a/drivers/media/platform/atmel/atmel-isc-base.c
+++ b/drivers/media/platform/atmel/atmel-isc-base.c
@@ -696,6 +696,7 @@ static void isc_stop_streaming(struct vb2_queue *vq)
 	struct isc_buffer *buf;
 	int ret;
 
+	mutex_lock(&isc->awb_mutex);
 	v4l2_ctrl_activate(isc->do_wb_ctrl, false);
 
 	isc->stop = true;
@@ -705,6 +706,8 @@ static void isc_stop_streaming(struct vb2_queue *vq)
 		v4l2_err(&isc->v4l2_dev,
 			 "Timeout waiting for end of the capture\n");
 
+	mutex_unlock(&isc->awb_mutex);
+
 	/* Disable DMA interrupt */
 	regmap_write(isc->regmap, ISC_INTDIS, ISC_INT_DDONE);
 
@@ -1696,10 +1699,6 @@ static void isc_awb_work(struct work_struct *w)
 	u32 min, max;
 	int ret;
 
-	/* streaming is not active anymore */
-	if (isc->stop)
-		return;
-
 	if (ctrls->hist_stat != HIST_ENABLED)
 		return;
 
@@ -1750,7 +1749,24 @@ static void isc_awb_work(struct work_struct *w)
 	}
 	regmap_write(regmap, ISC_HIS_CFG + isc->offsets.his,
 		     hist_id | baysel | ISC_HIS_CFG_RAR);
+
+	/*
+	 * We have to make sure the streaming has not stopped meanwhile.
+	 * ISC requires a frame to clock the internal profile update.
+	 * To avoid issues, lock the sequence with a mutex
+	 */
+	mutex_lock(&isc->awb_mutex);
+
+	/* streaming is not active anymore */
+	if (isc->stop) {
+		mutex_unlock(&isc->awb_mutex);
+		return;
+	};
+
 	isc_update_profile(isc);
+
+	mutex_unlock(&isc->awb_mutex);
+
 	/* if awb has been disabled, we don't need to start another histogram */
 	if (ctrls->awb)
 		regmap_write(regmap, ISC_CTRLEN, ISC_CTRL_HISREQ);
@@ -1829,6 +1845,7 @@ static int isc_s_awb_ctrl(struct v4l2_ctrl *ctrl)
 
 		isc_update_awb_ctrls(isc);
 
+		mutex_lock(&isc->awb_mutex);
 		if (vb2_is_streaming(&isc->vb2_vidq)) {
 			/*
 			 * If we are streaming, we can update profile to
@@ -1843,6 +1860,7 @@ static int isc_s_awb_ctrl(struct v4l2_ctrl *ctrl)
 			 */
 			v4l2_ctrl_activate(isc->do_wb_ctrl, false);
 		}
+		mutex_unlock(&isc->awb_mutex);
 
 		/* if we have autowhitebalance on, start histogram procedure */
 		if (ctrls->awb == ISC_WB_AUTO &&
@@ -2024,6 +2042,7 @@ static void isc_async_unbind(struct v4l2_async_notifier *notifier,
 {
 	struct isc_device *isc = container_of(notifier->v4l2_dev,
 					      struct isc_device, v4l2_dev);
+	mutex_destroy(&isc->awb_mutex);
 	cancel_work_sync(&isc->awb_work);
 	video_unregister_device(&isc->video_dev);
 	v4l2_ctrl_handler_free(&isc->ctrls.handler);
@@ -2133,6 +2152,8 @@ static int isc_async_complete(struct v4l2_async_notifier *notifier)
 	isc->current_subdev = container_of(notifier,
 					   struct isc_subdev_entity, notifier);
 	mutex_init(&isc->lock);
+	mutex_init(&isc->awb_mutex);
+
 	init_completion(&isc->comp);
 
 	/* Initialize videobuf2 queue */
@@ -2201,6 +2222,7 @@ static int isc_async_complete(struct v4l2_async_notifier *notifier)
 	return 0;
 
 isc_async_complete_err:
+	mutex_destroy(&isc->awb_mutex);
 	mutex_destroy(&isc->lock);
 	return ret;
 }
diff --git a/drivers/media/platform/atmel/atmel-isc.h b/drivers/media/platform/atmel/atmel-isc.h
index b0211100a5f23..0c3a452dafe33 100644
--- a/drivers/media/platform/atmel/atmel-isc.h
+++ b/drivers/media/platform/atmel/atmel-isc.h
@@ -207,6 +207,7 @@ struct isc_reg_offsets {
  *
  * @lock:		lock for serializing userspace file operations
  *			with ISC operations
+ * @awb_mutex:		serialize access to streaming status from awb work queue
  * @awb_lock:		lock for serializing awb work queue operations
  *			with DMA/buffer operations
  *
@@ -279,6 +280,7 @@ struct isc_device {
 	struct work_struct	awb_work;
 
 	struct mutex		lock;
+	struct mutex		awb_mutex;
 	spinlock_t		awb_lock;
 
 	struct regmap_field	*pipeline[ISC_PIPE_LINE_NODE_NUM];
-- 
2.53.0

[PATCH 5.15.y 3/3] media: microchip-isc: do not touch WB registers when not streaming

[Sasha Levin]

From: Balakrishnan Sambath <balakrishnan.s@microchip.com>

[ Upstream commit d8983c47d4d95eb1ed889dbb7516d3738fa854d8 ]

isc_s_awb_ctrl() called isc_update_awb_ctrls() unconditionally, writing
the white balance registers even when the device is runtime suspended;
on many ARM platforms accessing the unclocked registers is an external
abort. The write was also done without awb_lock, racing isc_awb_work(),
which holds it so the DMA done IRQ cannot latch a half-updated pipeline.

Write the registers only while streaming and not stopping, under
awb_lock, and update the profile there. The isc->stop check covers the
window where isc_stop_streaming() has gated the clocks but vb2 still
reports streaming. Otherwise the new values stay cached and
isc_configure() programs them at the next stream start.

Fixes: 4e52889f48fe ("media: atmel: atmel-isc-base: expose white balance as v4l2 controls")
Cc: stable@vger.kernel.org
Reviewed-by: Eugen Hristev <ehristev@kernel.org>
Signed-off-by: Balakrishnan Sambath <balakrishnan.s@microchip.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/media/platform/atmel/atmel-isc-base.c | 20 +++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/media/platform/atmel/atmel-isc-base.c b/drivers/media/platform/atmel/atmel-isc-base.c
index 565719fda13c3..dc12424965f3e 100644
--- a/drivers/media/platform/atmel/atmel-isc-base.c
+++ b/drivers/media/platform/atmel/atmel-isc-base.c
@@ -1843,20 +1843,24 @@ static int isc_s_awb_ctrl(struct v4l2_ctrl *ctrl)
 		if (ctrl->cluster[ISC_CTRL_GB_OFF]->is_new)
 			ctrls->offset[ISC_HIS_CFG_MODE_GB] = isc->gb_off_ctrl->val;
 
-		isc_update_awb_ctrls(isc);
-
 		mutex_lock(&isc->awb_mutex);
-		if (vb2_is_streaming(&isc->vb2_vidq)) {
+		if (vb2_is_streaming(&isc->vb2_vidq) && !isc->stop) {
+			unsigned long flags;
+
 			/*
-			 * If we are streaming, we can update profile to
-			 * have the new settings in place.
+			 * awb_lock keeps the DMA done IRQ from latching a
+			 * partially written WB pipeline.
 			 */
+			spin_lock_irqsave(&isc->awb_lock, flags);
+			isc_update_awb_ctrls(isc);
+			spin_unlock_irqrestore(&isc->awb_lock, flags);
+
 			isc_update_profile(isc);
 		} else {
 			/*
-			 * The auto cluster will activate automatically this
-			 * control. This has to be deactivated when not
-			 * streaming.
+			 * Not streaming: keep the cached values for the next
+			 * stream start and deactivate the cluster-activated
+			 * do_white_balance button.
 			 */
 			v4l2_ctrl_activate(isc->do_wb_ctrl, false);
 		}
-- 
2.53.0