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

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Message-ID: <1940906.PYKUYFuaPT@jernej-laptop>
Date:   Tue, 12 Sep 2023 17:51:07 +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 torek, 12. september 2023 ob 10:41:10 CEST je Benjamin Gaignard 
napisal(a):
> Le 11/09/2023 à 18:36, Jernej Škrabec a écrit :
> > 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.
> 
> The old code is wrong ;-)
> If the format depth is 10 bits per pixel then chroma offset (in bytes)
> formula is width * height * 10 / 8 not width * height * 16 / 8.
> 
> I have already confirm that with HEVC on the same hardware.

Ok, mention of bit_depth issue in commit log would be great. It talks only 
about width and height.

In any case, are width and/or height always dividable by 8?

Best regards,
Jernej

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