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Date:   Mon, 16 Nov 2020 00:25:22 +0500
From:   Bilal Wasim <bilalwasim676@gmail.com>
To:     Chun-Kuang Hu <chunkuang.hu@kernel.org>
Cc:     Jitao Shi <jitao.shi@mediatek.com>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@lists.infradead.org>, CK Hu <ck.hu@mediatek.com>
Subject: Re: [PATCH] drm/mediatek: dsi: Calculate horizontal_backporch_byte
 by itself
Message-ID: <20201116002522.1a5c3736@a-VirtualBox>
In-Reply-To: <CAAOTY_-16s=NXg2kOJijhO+82nNsT9HkKj4PVh1qN8dKchBOBA@mail.gmail.com>
References: <20201115001403.7833-1-chunkuang.hu@kernel.org>
        <CAAOTY_-16s=NXg2kOJijhO+82nNsT9HkKj4PVh1qN8dKchBOBA@mail.gmail.com>
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Hi CK,=20

On Sun, 15 Nov 2020 08:53:24 +0800
Chun-Kuang Hu <chunkuang.hu@kernel.org> wrote:

> Hi, Bilal:
>=20
> Please help to test this patch on your Chromebook elm, thanks.
>=20
> Regards,
> Chun-Kuang Hu

Just tried this patch on the Chromebook Elm, and it doesn't work. The
HDMI screen remains black, though the rest of the system keeps on
operating normally.

>=20
> Chun-Kuang Hu <chunkuang.hu@kernel.org> =E6=96=BC 2020=E5=B9=B411=E6=9C=
=8815=E6=97=A5 =E9=80=B1=E6=97=A5
> =E4=B8=8A=E5=8D=888:14=E5=AF=AB=E9=81=93=EF=BC=9A
> >
> > From: CK Hu <ck.hu@mediatek.com>
> >
> > Using vm->hfront_porch + vm->hback_porch to calculate
> > horizontal_backporch_byte would make it negtive, so
> > use horizontal_backporch_byte itself to make it positive.
> >
> > Fixes: 35bf948f1edb ("drm/mediatek: dsi: Fix scrolling of panel
> > with small hfp or hbp")
> >
> > Signed-off-by: CK Hu <ck.hu@mediatek.com>
> > Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>
> > ---
> >  drivers/gpu/drm/mediatek/mtk_dsi.c | 53
> > ++++++++++-------------------- 1 file changed, 18 insertions(+), 35
> > deletions(-)
> >
> > diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > b/drivers/gpu/drm/mediatek/mtk_dsi.c index
> > 4a188a942c38..2a64fdaed9a7 100644 ---
> > a/drivers/gpu/drm/mediatek/mtk_dsi.c +++
> > b/drivers/gpu/drm/mediatek/mtk_dsi.c @@ -444,7 +444,10 @@ static
> > void mtk_dsi_config_vdo_timing(struct mtk_dsi *dsi) u32
> > horizontal_sync_active_byte; u32 horizontal_backporch_byte;
> >         u32 horizontal_frontporch_byte;
> > +       u32 horizontal_front_back_byte;
> > +       u32 data_phy_cycles_byte;
> >         u32 dsi_tmp_buf_bpp, data_phy_cycles;
> > +       u32 delta;
> >         struct mtk_phy_timing *timing =3D &dsi->phy_timing;
> >
> >         struct videomode *vm =3D &dsi->vm;
> > @@ -474,42 +477,22 @@ static void mtk_dsi_config_vdo_timing(struct
> > mtk_dsi *dsi) data_phy_cycles =3D timing->lpx + timing->da_hs_prepare
> > + 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_bpp >
> > -                   data_phy_cycles * dsi->lanes + 18) {
> > -                       horizontal_frontporch_byte =3D
> > -                               vm->hfront_porch * dsi_tmp_buf_bpp -
> > -                               (data_phy_cycles * dsi->lanes + 18)
> > *
> > -                               vm->hfront_porch /
> > -                               (vm->hfront_porch +
> > vm->hback_porch); -
> > -                       horizontal_backporch_byte =3D
> > -                               horizontal_backporch_byte -
> > -                               (data_phy_cycles * dsi->lanes + 18)
> > *
> > -                               vm->hback_porch /
> > -                               (vm->hfront_porch +
> > vm->hback_porch);
> > -               } else {
> > -                       DRM_WARN("HFP less than d-phy, FPS will
> > under 60Hz\n");
> > -                       horizontal_frontporch_byte =3D
> > vm->hfront_porch *
> > -
> > dsi_tmp_buf_bpp;
> > -               }
> > +       delta =3D dsi->mode_flags & MIPI_DSI_MODE_VIDEO_BURST ? 18 :
> > 12; +
> > +       horizontal_frontporch_byte =3D vm->hfront_porch *
> > dsi_tmp_buf_bpp;
> > +       horizontal_front_back_byte =3D horizontal_frontporch_byte +
> > horizontal_backporch_byte;
> > +       data_phy_cycles_byte =3D data_phy_cycles * dsi->lanes + delta;
> > +
> > +       if (horizontal_front_back_byte > data_phy_cycles_byte) {
> > +               horizontal_frontporch_byte -=3D data_phy_cycles_byte *
> > +
> > horizontal_frontporch_byte /
> > +
> > horizontal_front_back_byte; +
> > +               horizontal_backporch_byte -=3D data_phy_cycles_byte *
> > +
> > horizontal_backporch_byte /
> > +
> > horizontal_front_back_byte; } else {
> > -               if ((vm->hfront_porch + vm->hback_porch) *
> > dsi_tmp_buf_bpp >
> > -                   data_phy_cycles * dsi->lanes + 12) {
> > -                       horizontal_frontporch_byte =3D
> > -                               vm->hfront_porch * dsi_tmp_buf_bpp -
> > -                               (data_phy_cycles * dsi->lanes + 12)
> > *
> > -                               vm->hfront_porch /
> > -                               (vm->hfront_porch +
> > vm->hback_porch);
> > -                       horizontal_backporch_byte =3D
> > horizontal_backporch_byte -
> > -                               (data_phy_cycles * dsi->lanes + 12)
> > *
> > -                               vm->hback_porch /
> > -                               (vm->hfront_porch +
> > vm->hback_porch);
> > -               } else {
> > -                       DRM_WARN("HFP less than d-phy, FPS will
> > under 60Hz\n");
> > -                       horizontal_frontporch_byte =3D
> > vm->hfront_porch *
> > -
> > dsi_tmp_buf_bpp;
> > -               }
> > +               DRM_WARN("HFP + HBP less than d-phy, FPS will under
> > 60Hz\n"); }
> >
> >         writel(horizontal_sync_active_byte, dsi->regs + DSI_HSA_WC);
> > --
> > 2.17.1
> > =20

Thanks,
Bilal