rcar_vin video buffer management fixes, v3

rcar_vin video buffer management fixes, v3

[William Towle]

  This is version 3 of the hotfix patchset for video support on Lager,
in which we aim to fix the kernel's warnings about unexpected buffer
states. It replaces the following series:
	http://comments.gmane.org/gmane.linux.drivers.video-input-infrastructure/87009

  This version of the series contains two patches which add a helper
function and then refactors the code where it is called, respectively.
Based on recent feedback, further modification is included in the
second patch where initialise/cleanup routines are removed due to
all significant content having moved elsewhere.

  The series comprises:
	[PATCH 1/2] media: rcar_vin: helper function for streaming stop
	[PATCH 2/2] media: rcar_vin: move buffer management to

Cheers,
  Wills

[PATCH 1/2] media: rcar_vin: helper function for streaming stop

[William Towle]

From: Ian Molton <ian.molton@codethink.co.uk>

The code that tests that capture from a stream has stopped is
presently insufficient and the potential for a race condition
exists where frame capture may generate an interrupt between
requesting the capture process halt and freeing buffers.

This patch refactors code out of rcar_vin_videobuf_release() and
into rcar_vin_wait_stop_streaming(), and ensures there are calls
in places where we need to know that capturing has finished.

Signed-off-by: Ian Molton <ian.molton@codethink.co.uk>
Signed-off-by: William Towle <william.towle@codethink.co.uk>
---
 drivers/media/platform/soc_camera/rcar_vin.c |   41 +++++++++++++++++---------
 1 file changed, 27 insertions(+), 14 deletions(-)

diff --git a/drivers/media/platform/soc_camera/rcar_vin.c b/drivers/media/platform/soc_camera/rcar_vin.c
index 8d8438b..89c409b 100644
--- a/drivers/media/platform/soc_camera/rcar_vin.c
+++ b/drivers/media/platform/soc_camera/rcar_vin.c
@@ -458,6 +458,28 @@ error:
 	vb2_buffer_done(vb, VB2_BUF_STATE_ERROR);
 }
 
+/*
+ * Wait for capture to stop and all in-flight buffers to be finished with by
+ * the video hardware. This must be called under &priv->lock
+ *
+ */
+static void rcar_vin_wait_stop_streaming(struct rcar_vin_priv *priv)
+{
+	while (priv->state != STOPPED) {
+		/* issue stop if running */
+		if (priv->state == RUNNING)
+			rcar_vin_request_capture_stop(priv);
+
+		/* wait until capturing has been stopped */
+		if (priv->state == STOPPING) {
+			priv->request_to_stop = true;
+			spin_unlock_irq(&priv->lock);
+			wait_for_completion(&priv->capture_stop);
+			spin_lock_irq(&priv->lock);
+		}
+	}
+}
+
 static void rcar_vin_videobuf_release(struct vb2_buffer *vb)
 {
 	struct soc_camera_device *icd = soc_camera_from_vb2q(vb->vb2_queue);
@@ -477,20 +499,8 @@ static void rcar_vin_videobuf_release(struct vb2_buffer *vb)
 	}
 
 	if (buf_in_use) {
-		while (priv->state != STOPPED) {
-
-			/* issue stop if running */
-			if (priv->state == RUNNING)
-				rcar_vin_request_capture_stop(priv);
-
-			/* wait until capturing has been stopped */
-			if (priv->state == STOPPING) {
-				priv->request_to_stop = true;
-				spin_unlock_irq(&priv->lock);
-				wait_for_completion(&priv->capture_stop);
-				spin_lock_irq(&priv->lock);
-			}
-		}
+		rcar_vin_wait_stop_streaming(priv);
+
 		/*
 		 * Capturing has now stopped. The buffer we have been asked
 		 * to release could be any of the current buffers in use, so
@@ -524,8 +534,11 @@ static void rcar_vin_stop_streaming(struct vb2_queue *vq)
 	struct list_head *buf_head, *tmp;
 
 	spin_lock_irq(&priv->lock);
+
+	rcar_vin_wait_stop_streaming(priv);
 	list_for_each_safe(buf_head, tmp, &priv->capture)
 		list_del_init(buf_head);
+
 	spin_unlock_irq(&priv->lock);
 }
 
-- 
1.7.10.4

[PATCH 2/2] media: rcar_vin: move buffer management to .stop_streaming handler

[William Towle]

This commit moves the "buffer in use" logic from the .buf_cleanup
handler into .stop_streaming, based on advice that this is its
proper logical home.

By ensuring the list of pointers in priv->queue_buf[] is managed
as soon as possible, we avoid warnings concerning buffers in ACTIVE
state when the system cleans up after streaming stops. This fixes a
problem with modification of buffers after their content has been
cleared for passing to userspace.

After the refactoring, the buf_init and buf_cleanup functions were
found to contain only initialisation/release steps as are carried out
elsewhere if omitted; these functions and references were removed.

Signed-off-by: William Towle <william.towle@codethink.co.uk>
---
 drivers/media/platform/soc_camera/rcar_vin.c |   62 ++++++--------------------
 1 file changed, 13 insertions(+), 49 deletions(-)

diff --git a/drivers/media/platform/soc_camera/rcar_vin.c b/drivers/media/platform/soc_camera/rcar_vin.c
index 89c409b..aa25a3b 100644
--- a/drivers/media/platform/soc_camera/rcar_vin.c
+++ b/drivers/media/platform/soc_camera/rcar_vin.c
@@ -480,72 +480,36 @@ static void rcar_vin_wait_stop_streaming(struct rcar_vin_priv *priv)
 	}
 }
 
-static void rcar_vin_videobuf_release(struct vb2_buffer *vb)
+static void rcar_vin_stop_streaming(struct vb2_queue *vq)
 {
-	struct soc_camera_device *icd = soc_camera_from_vb2q(vb->vb2_queue);
+	struct soc_camera_device *icd = soc_camera_from_vb2q(vq);
 	struct soc_camera_host *ici = to_soc_camera_host(icd->parent);
 	struct rcar_vin_priv *priv = ici->priv;
-	unsigned int i;
-	int buf_in_use = 0;
+	struct list_head *buf_head, *tmp;
+	int i;
 
 	spin_lock_irq(&priv->lock);
+	rcar_vin_wait_stop_streaming(priv);
 
-	/* Is the buffer in use by the VIN hardware? */
 	for (i = 0; i < MAX_BUFFER_NUM; i++) {
-		if (priv->queue_buf[i] == vb) {
-			buf_in_use = 1;
-			break;
-		}
-	}
-
-	if (buf_in_use) {
-		rcar_vin_wait_stop_streaming(priv);
-
-		/*
-		 * Capturing has now stopped. The buffer we have been asked
-		 * to release could be any of the current buffers in use, so
-		 * release all buffers that are in use by HW
-		 */
-		for (i = 0; i < MAX_BUFFER_NUM; i++) {
-			if (priv->queue_buf[i]) {
-				vb2_buffer_done(priv->queue_buf[i],
+		if (priv->queue_buf[i]) {
+			vb2_buffer_done(priv->queue_buf[i],
 					VB2_BUF_STATE_ERROR);
-				priv->queue_buf[i] = NULL;
-			}
+			priv->queue_buf[i] = NULL;
 		}
-	} else {
-		list_del_init(to_buf_list(vb));
 	}
 
-	spin_unlock_irq(&priv->lock);
-}
-
-static int rcar_vin_videobuf_init(struct vb2_buffer *vb)
-{
-	INIT_LIST_HEAD(to_buf_list(vb));
-	return 0;
-}
-
-static void rcar_vin_stop_streaming(struct vb2_queue *vq)
-{
-	struct soc_camera_device *icd = soc_camera_from_vb2q(vq);
-	struct soc_camera_host *ici = to_soc_camera_host(icd->parent);
-	struct rcar_vin_priv *priv = ici->priv;
-	struct list_head *buf_head, *tmp;
-
-	spin_lock_irq(&priv->lock);
-
-	rcar_vin_wait_stop_streaming(priv);
-	list_for_each_safe(buf_head, tmp, &priv->capture)
+	list_for_each_safe(buf_head, tmp, &priv->capture) {
+		vb2_buffer_done(&list_entry(buf_head,
+					struct rcar_vin_buffer, list)->vb,
+				VB2_BUF_STATE_ERROR);
 		list_del_init(buf_head);
-
+	}
 	spin_unlock_irq(&priv->lock);
 }
 
 static struct vb2_ops rcar_vin_vb2_ops = {
 	.queue_setup	= rcar_vin_videobuf_setup,
-	.buf_init	= rcar_vin_videobuf_init,
-	.buf_cleanup	= rcar_vin_videobuf_release,
 	.buf_queue	= rcar_vin_videobuf_queue,
 	.stop_streaming	= rcar_vin_stop_streaming,
 	.wait_prepare	= soc_camera_unlock,
-- 
1.7.10.4

[PATCH 2/2] media: rcar_vin: move buffer management to .stop_streaming handler

[William Towle]

This commit moves the "buffer in use" logic from the .buf_cleanup
handler into .stop_streaming, based on advice that this is its
proper logical home.

By ensuring the list of pointers in priv->queue_buf[] is managed
as soon as possible, we avoid warnings concerning buffers in ACTIVE
state when the system cleans up after streaming stops. This fixes a
problem with modification of buffers after their content has been
cleared for passing to userspace.

Signed-off-by: William Towle <william.towle@codethink.co.uk>
---
 drivers/media/platform/soc_camera/rcar_vin.c |   47 +++++++++-----------------
 1 file changed, 16 insertions(+), 31 deletions(-)

diff --git a/drivers/media/platform/soc_camera/rcar_vin.c b/drivers/media/platform/soc_camera/rcar_vin.c
index 89c409b..022fa9d 100644
--- a/drivers/media/platform/soc_camera/rcar_vin.c
+++ b/drivers/media/platform/soc_camera/rcar_vin.c
@@ -485,37 +485,10 @@ static void rcar_vin_videobuf_release(struct vb2_buffer *vb)
 	struct soc_camera_device *icd = soc_camera_from_vb2q(vb->vb2_queue);
 	struct soc_camera_host *ici = to_soc_camera_host(icd->parent);
 	struct rcar_vin_priv *priv = ici->priv;
-	unsigned int i;
-	int buf_in_use = 0;
 
 	spin_lock_irq(&priv->lock);
 
-	/* Is the buffer in use by the VIN hardware? */
-	for (i = 0; i < MAX_BUFFER_NUM; i++) {
-		if (priv->queue_buf[i] == vb) {
-			buf_in_use = 1;
-			break;
-		}
-	}
-
-	if (buf_in_use) {
-		rcar_vin_wait_stop_streaming(priv);
-
-		/*
-		 * Capturing has now stopped. The buffer we have been asked
-		 * to release could be any of the current buffers in use, so
-		 * release all buffers that are in use by HW
-		 */
-		for (i = 0; i < MAX_BUFFER_NUM; i++) {
-			if (priv->queue_buf[i]) {
-				vb2_buffer_done(priv->queue_buf[i],
-					VB2_BUF_STATE_ERROR);
-				priv->queue_buf[i] = NULL;
-			}
-		}
-	} else {
-		list_del_init(to_buf_list(vb));
-	}
+	list_del_init(to_buf_list(vb));
 
 	spin_unlock_irq(&priv->lock);
 }
@@ -532,13 +505,25 @@ static void rcar_vin_stop_streaming(struct vb2_queue *vq)
 	struct soc_camera_host *ici = to_soc_camera_host(icd->parent);
 	struct rcar_vin_priv *priv = ici->priv;
 	struct list_head *buf_head, *tmp;
+	int i;
 
 	spin_lock_irq(&priv->lock);
-
 	rcar_vin_wait_stop_streaming(priv);
-	list_for_each_safe(buf_head, tmp, &priv->capture)
-		list_del_init(buf_head);
 
+	for (i = 0; i < MAX_BUFFER_NUM; i++) {
+		if (priv->queue_buf[i]) {
+			vb2_buffer_done(priv->queue_buf[i],
+					VB2_BUF_STATE_ERROR);
+			priv->queue_buf[i] = NULL;
+		}
+	}
+
+	list_for_each_safe(buf_head, tmp, &priv->capture) {
+		vb2_buffer_done(&list_entry(buf_head,
+					struct rcar_vin_buffer, list)->vb,
+				VB2_BUF_STATE_ERROR);
+		list_del_init(buf_head);
+	}
 	spin_unlock_irq(&priv->lock);
 }
 
-- 
1.7.10.4

[PATCH 2/2] media: rcar_vin: move buffer management to .stop_streaming handler

[William Towle]

This commit moves the "buffer in use" logic from the .buf_cleanup
handler into .stop_streaming, based on advice that this is its
proper logical home.

By ensuring the list of pointers in priv->queue_buf[] is managed
as soon as possible, we avoid warnings concerning buffers in ACTIVE
state when the system cleans up after streaming stops. This fixes a
problem with modification of buffers after their content has been
cleared for passing to userspace.

Signed-off-by: William Towle <william.towle@codethink.co.uk>
---
 drivers/media/platform/soc_camera/rcar_vin.c |   47 +++++++++-----------------
 1 file changed, 16 insertions(+), 31 deletions(-)

diff --git a/drivers/media/platform/soc_camera/rcar_vin.c b/drivers/media/platform/soc_camera/rcar_vin.c
index 89c409b..022fa9d 100644
--- a/drivers/media/platform/soc_camera/rcar_vin.c
+++ b/drivers/media/platform/soc_camera/rcar_vin.c
@@ -485,37 +485,10 @@ static void rcar_vin_videobuf_release(struct vb2_buffer *vb)
 	struct soc_camera_device *icd = soc_camera_from_vb2q(vb->vb2_queue);
 	struct soc_camera_host *ici = to_soc_camera_host(icd->parent);
 	struct rcar_vin_priv *priv = ici->priv;
-	unsigned int i;
-	int buf_in_use = 0;
 
 	spin_lock_irq(&priv->lock);
 
-	/* Is the buffer in use by the VIN hardware? */
-	for (i = 0; i < MAX_BUFFER_NUM; i++) {
-		if (priv->queue_buf[i] == vb) {
-			buf_in_use = 1;
-			break;
-		}
-	}
-
-	if (buf_in_use) {
-		rcar_vin_wait_stop_streaming(priv);
-
-		/*
-		 * Capturing has now stopped. The buffer we have been asked
-		 * to release could be any of the current buffers in use, so
-		 * release all buffers that are in use by HW
-		 */
-		for (i = 0; i < MAX_BUFFER_NUM; i++) {
-			if (priv->queue_buf[i]) {
-				vb2_buffer_done(priv->queue_buf[i],
-					VB2_BUF_STATE_ERROR);
-				priv->queue_buf[i] = NULL;
-			}
-		}
-	} else {
-		list_del_init(to_buf_list(vb));
-	}
+	list_del_init(to_buf_list(vb));
 
 	spin_unlock_irq(&priv->lock);
 }
@@ -532,13 +505,25 @@ static void rcar_vin_stop_streaming(struct vb2_queue *vq)
 	struct soc_camera_host *ici = to_soc_camera_host(icd->parent);
 	struct rcar_vin_priv *priv = ici->priv;
 	struct list_head *buf_head, *tmp;
+	int i;
 
 	spin_lock_irq(&priv->lock);
-
 	rcar_vin_wait_stop_streaming(priv);
-	list_for_each_safe(buf_head, tmp, &priv->capture)
-		list_del_init(buf_head);
 
+	for (i = 0; i < MAX_BUFFER_NUM; i++) {
+		if (priv->queue_buf[i]) {
+			vb2_buffer_done(priv->queue_buf[i],
+					VB2_BUF_STATE_ERROR);
+			priv->queue_buf[i] = NULL;
+		}
+	}
+
+	list_for_each_safe(buf_head, tmp, &priv->capture) {
+		vb2_buffer_done(&list_entry(buf_head,
+					struct rcar_vin_buffer, list)->vb,
+				VB2_BUF_STATE_ERROR);
+		list_del_init(buf_head);
+	}
 	spin_unlock_irq(&priv->lock);
 }
 
-- 
1.7.10.4