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From:   Jernej =?utf-8?B?xaBrcmFiZWM=?= <jernej.skrabec@gmail.com>
To:     mchehab@kernel.org, tfiga@chromium.org, m.szyprowski@samsung.com,
        ming.qian@nxp.com, ezequiel@vanguardiasur.com.ar,
        p.zabel@pengutronix.de, gregkh@linuxfoundation.org,
        hverkuil-cisco@xs4all.nl, nicolas.dufresne@collabora.com,
        Benjamin Gaignard <benjamin.gaignard@collabora.com>
Cc:     linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, linux-arm-msm@vger.kernel.org,
        linux-rockchip@lists.infradead.org, linux-staging@lists.linux.dev,
        kernel@collabora.com
Subject: Re: [PATCH v6 14/18] media: verisilicon: vp9: Use destination buffer height
 to compute chroma offset
Date:   Tue, 12 Sep 2023 17:51:07 +0200
Message-ID: <1940906.PYKUYFuaPT@jernej-laptop>
In-Reply-To: <40329795-a57d-d0f3-adb4-0720dd20f6e2@collabora.com>
References: <20230901124414.48497-1-benjamin.gaignard@collabora.com>
 <3248154.aeNJFYEL58@jernej-laptop>
 <40329795-a57d-d0f3-adb4-0720dd20f6e2@collabora.com>
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Dne torek, 12. september 2023 ob 10:41:10 CEST je Benjamin Gaignard=20
napisal(a):
> Le 11/09/2023 =C3=A0 18:36, Jernej =C5=A0krabec a =C3=A9crit :
> > Dne ponedeljek, 11. september 2023 ob 10:55:02 CEST je Benjamin Gaignard
> >=20
> > napisal(a):
> >> Le 10/09/2023 =C3=A0 15:21, Jernej =C5=A0krabec a =C3=A9crit :
> >>> Hi Benjamin!
> >>>=20
> >>> Dne petek, 01. september 2023 ob 14:44:10 CEST je Benjamin Gaignard
> >>>=20
> >>> 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.
> >>>>=20
> >>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
> >>>> Fixes: e2da465455ce ("media: hantro: Support VP9 on the G2 core")
> >>>> ---
> >>>>=20
> >>>>    drivers/media/platform/verisilicon/hantro_g2_vp9_dec.c | 4 +---
> >>>>    1 file changed, 1 insertion(+), 3 deletions(-)
> >>>>=20
> >>>> 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 *ct=
x,
> >>>> const struct v4l2_ctrl_vp9_ static size_t chroma_offset(const struct
> >>>> hantro_ctx *ctx,
> >>>>=20
> >>>>    			    const struct v4l2_ctrl_vp9_frame
> >>>=20
> >>> *dec_params)
> >>>=20
> >>>>    {
> >>>>=20
> >>>> -	int bytes_per_pixel =3D dec_params->bit_depth =3D=3D 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 /
> >>>=20
> >>> 8;
> >>>=20
> >>> 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_dep=
th,
> >>> 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.
> >>=20
> >> 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.
> >=20
> > Solution is same as the code that you removed:
> > int bytes_per_pixel =3D dec_params->bit_depth =3D=3D 8 ? 1 : 2;
> >=20
> > Or alternatively:
> > int bytes_per_pixel =3D DIV_ROUND_UP(dec_params->bit_depth, 8);
> >=20
> > Consider bit_depth being 10. With old code you get 2, with yours you get
> > 1.
>=20
> 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.
>=20
> 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=
=20
about width and height.

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

Best regards,
Jernej

>=20
> Regards,
> Benjamin
>=20
> > Best regards,
> > Jernej
> >=20
> >> Regards,
> >> Benjamin
> >>=20
> >>> Best regards,
> >>> Jernej
> >>>=20
> >>>>    }
> >>>>   =20
> >>>>    static size_t mv_offset(const struct hantro_ctx *ctx,