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Date:   Tue, 17 Nov 2020 16:58:48 +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: <20201117165848.54eb2d87@a-VirtualBox>
In-Reply-To: <CAAOTY_8LOLg8BeVY39EciSPqtBzeafPpenm0721+2rfhkKH0Cw@mail.gmail.com>
References: <20201115001403.7833-1-chunkuang.hu@kernel.org>
        <CAAOTY_-16s=NXg2kOJijhO+82nNsT9HkKj4PVh1qN8dKchBOBA@mail.gmail.com>
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        <CAAOTY_-_N9pcmao0FFtGs-qVLrvA-QBz5FJrSaYynuMZMe1Qhg@mail.gmail.com>
        <20201116165311.15a36e82@a-VirtualBox>
        <CAAOTY_8LOLg8BeVY39EciSPqtBzeafPpenm0721+2rfhkKH0Cw@mail.gmail.com>
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Hi CK,

On Tue, 17 Nov 2020 00:43:44 +0800
Chun-Kuang Hu <chunkuang.hu@kernel.org> wrote:

> Hi, Bilal:
>=20
> Bilal Wasim <bilalwasim676@gmail.com> =E6=96=BC 2020=E5=B9=B411=E6=9C=881=
6=E6=97=A5 =E9=80=B1=E4=B8=80
> =E4=B8=8B=E5=8D=887:53=E5=AF=AB=E9=81=93=EF=BC=9A
> >
> > Hi CK,
> >
> > On Mon, 16 Nov 2020 07:12:55 +0800
> > Chun-Kuang Hu <chunkuang.hu@kernel.org> wrote:
> > =20
> > > Hi, Bilal:
> > >
> > > Bilal Wasim <bilalwasim676@gmail.com> =E6=96=BC 2020=E5=B9=B411=E6=9C=
=8816=E6=97=A5 =E9=80=B1=E4=B8=80
> > > =E4=B8=8A=E5=8D=883:25=E5=AF=AB=E9=81=93=EF=BC=9A =20
> > > >
> > > > Hi CK,
> > > >
> > > > On Sun, 15 Nov 2020 08:53:24 +0800
> > > > Chun-Kuang Hu <chunkuang.hu@kernel.org> wrote:
> > > > =20
> > > > > Hi, Bilal:
> > > > >
> > > > > Please help to test this patch on your Chromebook elm, thanks.
> > > > >
> > > > > Regards,
> > > > > Chun-Kuang Hu =20
> > > >
> > > > 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
> > >
> > > Could you print this information, so I could find out the
> > > solution for both small hbp and elm.
> > >
> > > vm->hfront_porch, vm->hback_porch, dsi_tmp_buf_bpp,
> > > data_phy_cycles_byte, and the final horizontal_frontporch_byte,
> > > horizontal_backporch_byte. =20
> >
> > Here are the values I got,
> >
> > [    2.506400] [drm] vm->hfront_porch: 48
> > [    2.506402] [drm] vm->hback_porch: 200
> > [    2.506404] [drm] dsi_tmp_buf_bpp: 3
> > [    2.506406] [drm] data_phy_cycles_byte: 180
> > [    2.506408] [drm] horizontal_frontporch_byte: 110
> > [    2.506409] [drm] horizontal_backporch_byte: 455
> >
> > Please let me know if I can help debug this in any other way.
> > =20
>=20
> How about this patch [1] ?
>=20
> [1]
> https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/=
+/2536217/2

This patch works, though it doesn't apply cleanly on 5.9-rc3 (had to
manually patch the mtk_dsi.c file).=20

Here are the various variable values, if you're interested.=20

[    2.453292] [drm] vm->hfront_porch: 48
[    2.453293] [drm] vm->hback_porch: 200
[    2.453295] [drm] dsi_tmp_buf_bpp: 3
[    2.453296] [drm] data_phy_cycles_byte: 192
[    2.453298] [drm] horizontal_frontporch_byte: 107
[    2.453299] [drm] horizontal_backporch_byte: 436

Thanks,=20
Bilal

>=20
> > Thanks,
> > Bilal
> > =20
> > >
> > > Regards,
> > > Chun-Kuang.
> > > =20
> > > > =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 =20
> > > > > >
> > > > > > 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 =20
> > =20