[PATCH] drm/mediatek: dsi: Calculate horizontal_backporch_byte by itself

[Bilal Wasim]

Hi CK, 

On Mon, 16 Nov 2020 07:12:55 +0800
Chun-Kuang Hu <chunkuang.hu at kernel.org> wrote:

> Hi, Bilal:
> 
> Bilal Wasim <bilalwasim676 at gmail.com> 於 2020年11月16日 週一
> 上午3:25寫道：
> >
> > Hi CK,
> >
> > On Sun, 15 Nov 2020 08:53:24 +0800
> > Chun-Kuang Hu <chunkuang.hu at kernel.org> wrote:
> >  
> > > Hi, Bilal:
> > >
> > > Please help to test this patch on your Chromebook elm, thanks.
> > >
> > > 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.  
> 
> 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.

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.

Thanks, 
Bilal

> 
> Regards,
> Chun-Kuang.
> 
> >  
> > >
> > > Chun-Kuang Hu <chunkuang.hu at kernel.org> 於 2020年11月15日 週日
> > > 上午8:14寫道：  
> > > >
> > > > From: CK Hu <ck.hu at 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 at mediatek.com>
> > > > Signed-off-by: Chun-Kuang Hu <chunkuang.hu at 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 = &dsi->phy_timing;
> > > >
> > > >         struct videomode *vm = &dsi->vm;
> > > > @@ -474,42 +477,22 @@ static void
> > > > mtk_dsi_config_vdo_timing(struct mtk_dsi *dsi) data_phy_cycles
> > > > = 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 =
> > > > -                               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 =
> > > > -                               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 =
> > > > vm->hfront_porch *
> > > > -
> > > > dsi_tmp_buf_bpp;
> > > > -               }
> > > > +       delta = dsi->mode_flags & MIPI_DSI_MODE_VIDEO_BURST ?
> > > > 18 : 12; +
> > > > +       horizontal_frontporch_byte = vm->hfront_porch *
> > > > dsi_tmp_buf_bpp;
> > > > +       horizontal_front_back_byte = horizontal_frontporch_byte
> > > > + horizontal_backporch_byte;
> > > > +       data_phy_cycles_byte = data_phy_cycles * dsi->lanes +
> > > > delta; +
> > > > +       if (horizontal_front_back_byte > data_phy_cycles_byte) {
> > > > +               horizontal_frontporch_byte -=
> > > > data_phy_cycles_byte * +
> > > > horizontal_frontporch_byte /
> > > > +
> > > > horizontal_front_back_byte; +
> > > > +               horizontal_backporch_byte -=
> > > > 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 =
> > > > -                               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 =
> > > > 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 =
> > > > 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
> > > >  
> >
> > Thanks,
> > Bilal