linux-kernel - Re: [PATCH v1 4/5] media: rkvdec: Re-enable H.264 error detection

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Date:   Fri, 10 Jun 2022 12:23:49 -0400
From:   Nicolas Dufresne <nicolas.dufresne@...labora.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     linux-media@...r.kernel.org,
        Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        kernel@...labora.com, linux-rockchip@...ts.infradead.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 4/5] media: rkvdec: Re-enable H.264 error detection

Le vendredi 10 juin 2022 à 16:20 +0300, Dan Carpenter a écrit :
> On Fri, Jun 10, 2022 at 08:52:14AM -0400, Nicolas Dufresne wrote:
> > This re-enables H.264 error detection, but using the other error mode.
> > In that mode, the decoder will skip over the error macro-block or
> > slices and complete the decoding. As a side effect, the error status
> > is not set in the interrupt status register, and instead errors are
> > detected per format. Using this mode workaround the issue that the
> > HW get stuck in error stated and allow reporting that some corruption
> > may be present in the buffer returned to userland.
> > 
> > Signed-off-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>
> > ---
> >  drivers/staging/media/rkvdec/rkvdec-h264.c | 23 +++++++++++++++++++---
> >  1 file changed, 20 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/staging/media/rkvdec/rkvdec-h264.c b/drivers/staging/media/rkvdec/rkvdec-h264.c
> > index 55596ce6bb6e..60a89918e2c1 100644
> > --- a/drivers/staging/media/rkvdec/rkvdec-h264.c
> > +++ b/drivers/staging/media/rkvdec/rkvdec-h264.c
> > @@ -1175,14 +1175,15 @@ static int rkvdec_h264_run(struct rkvdec_ctx *ctx)
> >  
> >  	schedule_delayed_work(&rkvdec->watchdog_work, msecs_to_jiffies(2000));
> >  
> > -	writel(0, rkvdec->regs + RKVDEC_REG_STRMD_ERR_EN);
> > -	writel(0, rkvdec->regs + RKVDEC_REG_H264_ERR_E);
> > +	writel(0xffffffff, rkvdec->regs + RKVDEC_REG_STRMD_ERR_EN);
> > +	writel(0xffffffff, rkvdec->regs + RKVDEC_REG_H264_ERR_E);
> 
> This reverts the changes in patch 1/5.  Could we just skip patch 1/5
> instead?

As documented, this is for back-porting purpose. The first patch is what has
been running for 7 years in Chromebook, so I'm fully confident it is safe to
backport it into our stable kernel. The second is like a new feature, which I'm
confident works, but didn't get as much testing as I just wrote it. So what I'm
doing here is giving a same thing to backport, and a better fix for the next
kernel. You are otherwise right that this will revert it.

Nicolas