[PATCH 2/2] media: nxp: imx8-isi: Prioritize pending buffers over discard buffers

[G.N. Zhou (OSS)]

Hi Frank,

Thanks for your review.

> -----Original Message-----
> From: Frank Li <frank.li at nxp.com>
> Sent: Wednesday, March 11, 2026 11:34 PM
> To: G.N. Zhou (OSS) <guoniu.zhou at oss.nxp.com>
> Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>; Mauro Carvalho
> Chehab <mchehab at kernel.org>; Sascha Hauer <s.hauer at pengutronix.de>;
> Pengutronix Kernel Team <kernel at pengutronix.de>; Fabio Estevam
> <festevam at gmail.com>; linux-media at vger.kernel.org; imx at lists.linux.dev;
> linux-arm-kernel at lists.infradead.org; linux-kernel at vger.kernel.org; Alexi
> Birlinger <alexi.birlinger at nxp.com>; G.N. Zhou <guoniu.zhou at nxp.com>
> Subject: Re: [PATCH 2/2] media: nxp: imx8-isi: Prioritize pending buffers over
> discard buffers
> 
> On Wed, Mar 11, 2026 at 04:02:59PM +0800, Guoniu Zhou wrote:
> > From: Guoniu Zhou <guoniu.zhou at nxp.com>
> >
> > Change the buffer selection logic to use pending buffers first (up to
> > the number available), and only use discard buffers to fill remaining
> > slots when insufficient pending buffers are queued. This ensures user
> > buffers
> 
> Nit: Ensure user ...

Will update.

> 
> > are utilized as soon as possible, improving efficiency and reducing
> > the number of discarded frames at stream start.
> >
> > For example:
> > - 2 pending buffers: both slots use pending buffers
> > - 1 pending buffer: first slot uses pending, second uses discard
> > - 0 pending buffers: both slots use discard buffers
> >
> > Signed-off-by: Guoniu Zhou <guoniu.zhou at nxp.com>
> > ---
> >  drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c
> > b/drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c
> > index
> >
> 2405baf21594cd18cf2b349234313c5e103b7802..53f4f74369f7855fe6b6f372
> 294e
> > e569f40a8ae6 100644
> > --- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c
> > +++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c
> > @@ -786,13 +786,14 @@ static void
> mxc_isi_video_queue_first_buffers(struct mxc_isi_video *video)
> >  		: list_is_singular(&video->out_pending) ? 1
> >  		: 0;
> >
> > +	/* Queue buffers: prioritize pending buffers, then discard buffers
> > +*/
> >  	for (i = 0; i < 2; ++i) {
> >  		enum mxc_isi_buf_id buf_id = i == 0 ? MXC_ISI_BUF1
> >  					   : MXC_ISI_BUF2;
> >  		struct mxc_isi_buffer *buf;
> >  		struct list_head *list;
> >
> > -		list = i < discard ? &video->out_discard : &video->out_pending;
> > +		list = (i < 2 - discard) ? &video->out_pending :
> > +&video->out_discard;
> 
> Is (2 - discard) the number of pending buffers? put commit's example as
> comments here.

Yes, will update in next version.

> 
> Frank
> 
> >  		buf = list_first_entry(list, struct mxc_isi_buffer, list);
> >
> >  		mxc_isi_channel_set_outbuf(video->pipe, buf->dma_addrs,
> buf_id);
> >
> > --
> > 2.34.1
> >