linux-kernel - Re: [PATCH v6 14/18] media: verisilicon: vp9: Use destination buffer height to compute chroma offset

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Message-ID: <3248154.aeNJFYEL58@jernej-laptop>
Date:   Mon, 11 Sep 2023 18:36:19 +0200
From:   Jernej Škrabec <jernej.skrabec@...il.com>
To:     mchehab@...nel.org, tfiga@...omium.org, m.szyprowski@...sung.com,
        ming.qian@....com, ezequiel@...guardiasur.com.ar,
        p.zabel@...gutronix.de, gregkh@...uxfoundation.org,
        hverkuil-cisco@...all.nl, nicolas.dufresne@...labora.com,
        Benjamin Gaignard <benjamin.gaignard@...labora.com>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, linux-staging@...ts.linux.dev,
        kernel@...labora.com
Subject: Re: [PATCH v6 14/18] media: verisilicon: vp9: Use destination buffer height
 to compute chroma offset

Dne ponedeljek, 11. september 2023 ob 10:55:02 CEST je Benjamin Gaignard 
napisal(a):
> Le 10/09/2023 à 15:21, Jernej Škrabec a écrit :
> > Hi Benjamin!
> > 
> > Dne petek, 01. september 2023 ob 14:44:10 CEST je Benjamin Gaignard
> > 
> > napisal(a):
> >> Source and destination buffer height may not be the same because
> >> alignment constraint are different.
> >> Use destination height to compute chroma offset because we target
> >> this buffer as hardware output.
> >> 
> >> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
> >> Fixes: e2da465455ce ("media: hantro: Support VP9 on the G2 core")
> >> ---
> >> 
> >>   drivers/media/platform/verisilicon/hantro_g2_vp9_dec.c | 4 +---
> >>   1 file changed, 1 insertion(+), 3 deletions(-)
> >> 
> >> diff --git a/drivers/media/platform/verisilicon/hantro_g2_vp9_dec.c
> >> b/drivers/media/platform/verisilicon/hantro_g2_vp9_dec.c index
> >> 6db1c32fce4d..1f3f5e7ce978 100644
> >> --- a/drivers/media/platform/verisilicon/hantro_g2_vp9_dec.c
> >> +++ b/drivers/media/platform/verisilicon/hantro_g2_vp9_dec.c
> >> @@ -93,9 +93,7 @@ static int start_prepare_run(struct hantro_ctx *ctx,
> >> const struct v4l2_ctrl_vp9_ static size_t chroma_offset(const struct
> >> hantro_ctx *ctx,
> >> 
> >>   			    const struct v4l2_ctrl_vp9_frame
> > 
> > *dec_params)
> > 
> >>   {
> >> 
> >> -	int bytes_per_pixel = dec_params->bit_depth == 8 ? 1 : 2;
> >> -
> >> -	return ctx->src_fmt.width * ctx->src_fmt.height * bytes_per_pixel;
> >> +	return ctx->dst_fmt.width * ctx->dst_fmt.height * ctx->bit_depth /
> > 
> > 8;
> > 
> > Commit message doesn't mention bit_depth change at all. While I think
> > there is no difference between dec_params->bit_depth and ctx->bit_depth,
> > you shouldn't just use ordinary division. If bit_depth is 10, it will be
> > rounded down. And if you decide to use bit_depth from context, please
> > remove dec_params argument.
> 
> I will change this patch and create a helpers function for chroma and motion
> vectors offsets that VP9 and HEVC code will use since they are identical.
> I don't see issue with the division. If you have in mind a solution please
> write it so I could test it.

Solution is same as the code that you removed:
int bytes_per_pixel = dec_params->bit_depth == 8 ? 1 : 2;

Or alternatively:
int bytes_per_pixel = DIV_ROUND_UP(dec_params->bit_depth, 8);

Consider bit_depth being 10. With old code you get 2, with yours you get 1.

Best regards,
Jernej

> 
> Regards,
> Benjamin
> 
> > Best regards,
> > Jernej
> > 
> >>   }
> >>   
> >>   static size_t mv_offset(const struct hantro_ctx *ctx,