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

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Message-ID: <40329795-a57d-d0f3-adb4-0720dd20f6e2@collabora.com>
Date:   Tue, 12 Sep 2023 10:41:10 +0200
From:   Benjamin Gaignard <benjamin.gaignard@...labora.com>
To:     Jernej Škrabec <jernej.skrabec@...il.com>,
        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
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


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.

Regards,
Benjamin

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