[PATCH v2] 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.

So, to avoid that, add an 'in_use' flag in the ctx structure that will
keep track whether the output/capture queues have been started or not,
and use it to avoid decrementing/incrementing the usage_count
unnecessarily.

Fixes: cf21f328fcafac ("media: nxp: Add i.MX8 ISI driver")
Signed-off-by: Laurentiu Palcu <laurentiu.palcu@xxxxxxxxxxx>
---
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;

 .../platform/nxp/imx8-isi/imx8-isi-m2m.c      | 24 +++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

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..3f06ae1349e53 100644
--- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-m2m.c
+++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-m2m.c
@@ -65,6 +65,7 @@ struct mxc_isi_m2m_ctx {
 	} ctrls;
 
 	bool chained;
+	bool in_use[2];
 };
 
 static inline struct mxc_isi_m2m_buffer *
@@ -491,6 +492,7 @@ static int mxc_isi_m2m_streamon(struct file *file, void *fh,
 	const struct mxc_isi_format_info *cap_info = ctx->queues.cap.info;
 	const struct mxc_isi_format_info *out_info = ctx->queues.out.info;
 	struct mxc_isi_m2m *m2m = ctx->m2m;
+	bool already_in_use;
 	bool bypass;
 
 	int ret;
@@ -502,6 +504,8 @@ static int mxc_isi_m2m_streamon(struct file *file, void *fh,
 		goto unlock;
 	}
 
+	already_in_use = ctx->in_use[type == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE];
+
 	bypass = cap_pix->width == out_pix->width &&
 		 cap_pix->height == out_pix->height &&
 		 cap_info->encoding == out_info->encoding;
@@ -520,7 +524,10 @@ static int mxc_isi_m2m_streamon(struct file *file, void *fh,
 		mxc_isi_channel_get(m2m->pipe);
 	}
 
-	m2m->usage_count++;
+	if (!already_in_use) {
+		m2m->usage_count++;
+		ctx->in_use[type == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE] = true;
+	}
 
 	/*
 	 * Allocate resources for the channel, counting how many users require
@@ -555,7 +562,12 @@ static int mxc_isi_m2m_streamon(struct file *file, void *fh,
 	ctx->chained = false;
 
 deinit:
-	if (--m2m->usage_count == 0) {
+	if (!already_in_use) {
+		m2m->usage_count--;
+		ctx->in_use[type == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE] = false;
+	}
+
+	if (m2m->usage_count == 0) {
 		mxc_isi_channel_put(m2m->pipe);
 		mxc_isi_channel_release(m2m->pipe);
 	}
@@ -575,6 +587,9 @@ static int mxc_isi_m2m_streamoff(struct file *file, void *fh,
 
 	mutex_lock(&m2m->lock);
 
+	if (!ctx->in_use[type == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE])
+		goto unlock;
+
 	/*
 	 * If the last context is this one, reset it to make sure the device
 	 * will be reconfigured when streaming is restarted.
@@ -587,6 +602,8 @@ static int mxc_isi_m2m_streamoff(struct file *file, void *fh,
 		mxc_isi_channel_unchain(m2m->pipe);
 	ctx->chained = false;
 
+	ctx->in_use[type == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE] = false;
+
 	/* Turn off the light with the last user. */
 	if (--m2m->usage_count == 0) {
 		mxc_isi_channel_disable(m2m->pipe);
@@ -594,8 +611,7 @@ static int mxc_isi_m2m_streamoff(struct file *file, void *fh,
 		mxc_isi_channel_release(m2m->pipe);
 	}
 
-	WARN_ON(m2m->usage_count < 0);
-
+unlock:
 	mutex_unlock(&m2m->lock);
 
 	return 0;
-- 
2.34.1