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From:   Chun-Kuang Hu <chunkuang.hu@kernel.org>
Date:   Tue, 18 Aug 2020 07:42:38 +0800
Message-ID: <CAAOTY_9ggDUdDD9KoOaWBx3XaK+=Q=5qxahG7SJ5uYBQZ4aadw@mail.gmail.com>
Subject: Re: [PATCH v2] drm/mediatek: dsi: fix scrolling of panel with small
 hfp or hbp
To:     Jitao Shi <jitao.shi@mediatek.com>
Cc:     Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@linux.ie>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        devicetree@vger.kernel.org,
        srv_heupstream <srv_heupstream@mediatek.com>,
        huijuan.xie@mediatek.com, stonea168@163.com,
        cawa.cheng@mediatek.com,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@lists.infradead.org>,
        Bibby Hsieh <bibby.hsieh@mediatek.com>,
        CK Hu <ck.hu@mediatek.com>, yingjoe.chen@mediatek.com,
        eddie.huang@mediatek.com,
        Linux ARM <linux-arm-kernel@lists.infradead.org>
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Hi, Jitao:

Jitao Shi <jitao.shi@mediatek.com> =E6=96=BC 2020=E5=B9=B48=E6=9C=8817=E6=
=97=A5 =E9=80=B1=E4=B8=80 =E4=B8=8B=E5=8D=889:07=E5=AF=AB=E9=81=93=EF=BC=9A
>
> horizontal_backporch_byte should be hbp * bpp - hbp extra bytes.
> So remove the wrong subtraction 10.
>
> Signed-off-by: Jitao Shi <jitao.shi@mediatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_dsi.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediate=
k/mtk_dsi.c
> index 270bf22c98fe..5d031e634571 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -473,14 +473,13 @@ static void mtk_dsi_config_vdo_timing(struct mtk_ds=
i *dsi)
>         horizontal_sync_active_byte =3D (vm->hsync_len * dsi_tmp_buf_bpp =
- 10);

So this subtraction 10 is correct?

Regards,
Chun-Kuang.

>
>         if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE)
> -               horizontal_backporch_byte =3D
> -                       (vm->hback_porch * dsi_tmp_buf_bpp - 10);
> +               horizontal_backporch_byte =3D vm->hback_porch * dsi_tmp_b=
uf_bpp;
>         else
> -               horizontal_backporch_byte =3D ((vm->hback_porch + vm->hsy=
nc_len) *
> -                       dsi_tmp_buf_bpp - 10);
> +               horizontal_backporch_byte =3D (vm->hback_porch + vm->hsyn=
c_len) *
> +                                           dsi_tmp_buf_bpp;
>
>         data_phy_cycles =3D timing->lpx + timing->da_hs_prepare +
> -                         timing->da_hs_zero + timing->da_hs_exit + 3;
> +                         timing->da_hs_zero + timing->da_hs_exit;
>
>         if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO_BURST) {
>                 if ((vm->hfront_porch + vm->hback_porch) * dsi_tmp_buf_bp=
p >
> --
> 2.12.5
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