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

Laurent Pinchart
2025-02-06T20:37:56Z

Hi Laurentiu,

Thank you for the patch.

On Wed, Oct 23, 2024 at 11:56:43AM +0300, Laurentiu Palcu wrote:
> 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@ideasonboard.com>
> Signed-off-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>
> ---
> 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,
>

While at it I'll drop the blank line here when applying the patch.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> 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;
> }
>

--
Regards,

Laurent Pinchart