[PATCH v3] media: nxp: imx8-isi: better handle the m2m usage_count

[Laurentiu Palcu <laurentiu.palcu@xxxxxxxxxxx>]

Currently, if streamon/streamoff calls are imbalanced we can either end up
with a negative ISI m2m usage_count (if streamoff() is called more times
than streamon()) in which case we'll not be able to restart the ISI pipe
next time, or the usage_count never gets to 0 and the pipe is never
switched off.

To avoid that, add a 'streaming' flag to mxc_isi_m2m_ctx_queue_data and use it
in the streamon/streamoff to avoid incrementing/decrementing the usage_count
uselessly, if called multiple times from the same context.

Fixes: cf21f328fcafac ("media: nxp: Add i.MX8 ISI driver")
Suggested-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Signed-off-by: Laurentiu Palcu <laurentiu.palcu@xxxxxxxxxxx>
---
v3:
 * Changed the implementation as suggested by Laurent and add a Suggested-by
   tag to reflect that;

v2:
 * Changed the way 'usage_count' is incremented/decremented by taking
   into account the context the streamon/streamoff functions are called
   from;
 * Changed the commit message and subject to reflect the changes;

 drivers/media/platform/nxp/imx8-isi/imx8-isi-m2m.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-m2m.c b/drivers/media/platform/nxp/imx8-isi/imx8-isi-m2m.c
index 9745d6219a166..dc10e1a9f27c1 100644
--- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-m2m.c
+++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-m2m.c
@@ -43,6 +43,7 @@ struct mxc_isi_m2m_ctx_queue_data {
 	struct v4l2_pix_format_mplane format;
 	const struct mxc_isi_format_info *info;
 	u32 sequence;
+	bool streaming;
 };
 
 struct mxc_isi_m2m_ctx {
@@ -486,6 +487,7 @@ static int mxc_isi_m2m_streamon(struct file *file, void *fh,
 				enum v4l2_buf_type type)
 {
 	struct mxc_isi_m2m_ctx *ctx = to_isi_m2m_ctx(fh);
+	struct mxc_isi_m2m_ctx_queue_data *q = mxc_isi_m2m_ctx_qdata(ctx, type);
 	const struct v4l2_pix_format_mplane *out_pix = &ctx->queues.out.format;
 	const struct v4l2_pix_format_mplane *cap_pix = &ctx->queues.cap.format;
 	const struct mxc_isi_format_info *cap_info = ctx->queues.cap.info;
@@ -495,6 +497,9 @@ static int mxc_isi_m2m_streamon(struct file *file, void *fh,
 
 	int ret;
 
+	if (q->streaming)
+		return 0;
+
 	mutex_lock(&m2m->lock);
 
 	if (m2m->usage_count == INT_MAX) {
@@ -547,6 +552,8 @@ static int mxc_isi_m2m_streamon(struct file *file, void *fh,
 		goto unchain;
 	}
 
+	q->streaming = true;
+
 	return 0;
 
 unchain:
@@ -569,10 +576,14 @@ static int mxc_isi_m2m_streamoff(struct file *file, void *fh,
 				 enum v4l2_buf_type type)
 {
 	struct mxc_isi_m2m_ctx *ctx = to_isi_m2m_ctx(fh);
+	struct mxc_isi_m2m_ctx_queue_data *q = mxc_isi_m2m_ctx_qdata(ctx, type);
 	struct mxc_isi_m2m *m2m = ctx->m2m;
 
 	v4l2_m2m_ioctl_streamoff(file, fh, type);
 
+	if (!q->streaming)
+		return 0;
+
 	mutex_lock(&m2m->lock);
 
 	/*
@@ -598,6 +609,8 @@ static int mxc_isi_m2m_streamoff(struct file *file, void *fh,
 
 	mutex_unlock(&m2m->lock);
 
+	q->streaming = false;
+
 	return 0;
 }
 
-- 
2.44.1