linux-kernel - Re: [PATCH v3] media: nxp: imx8-isi: better handle the m2m usage

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Message-ID: <uie4tvosmzq63qpi4fgengjfuodkzoy3th5zhurt4j4yt772ml@rpplzhmbiky5>
Date: Wed, 2 Apr 2025 09:45:57 +0300
From: Laurentiu Palcu <laurentiu.palcu@....nxp.com>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>, 
	Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, 
	Pengutronix Kernel Team <kernel@...gutronix.de>, Fabio Estevam <festevam@...il.com>, 
	Dong Aisheng <aisheng.dong@....com>, Jacopo Mondi <jacopo@...ndi.org>, 
	Christian Hemp <c.hemp@...tec.de>, Guoniu Zhou <guoniu.zhou@....com>, 
	Stefan Riedmueller <s.riedmueller@...tec.de>, linux-media@...r.kernel.org, imx@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] media: nxp: imx8-isi: better handle the m2m
 usage_count

Hi Laurent,

I'm really sorry to keep bugging you about this patch but it looks like
this one fell through the cracks again... :/

Thanks,
Laurentiu

On Thu, Feb 06, 2025 at 10:37:49PM +0200, Laurent Pinchart wrote:
> 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@...asonboard.com>
> > Signed-off-by: Laurentiu Palcu <laurentiu.palcu@....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@...asonboard.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