[PATCH v2] drm/mediatek: dsi: fix scrolling of panel with small hfp or hbp

[Jitao Shi]

On Tue, 2020-08-18 at 07:42 +0800, Chun-Kuang Hu wrote:
> Hi, Jitao:
> 
> Jitao Shi <jitao.shi at mediatek.com> 於 2020年8月17日 週一 下午9:07寫道：
> >
> > horizontal_backporch_byte should be hbp * bpp - hbp extra bytes.
> > So remove the wrong subtraction 10.
> >
> > Signed-off-by: Jitao Shi <jitao.shi at 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/mediatek/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_dsi *dsi)
> >         horizontal_sync_active_byte = (vm->hsync_len * dsi_tmp_buf_bpp - 10);
> 
> So this subtraction 10 is correct?
> 
> Regards,
> Chun-Kuang.
> 

Yes, It is right.

In the cea861 and dmt spec the mini hsync is 40 pixels.
So the vm->hsync_len * dsi_tmp_buf_bpp >= 120 > 10

Best Regards
jitao
> >
> >         if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE)
> > -               horizontal_backporch_byte =
> > -                       (vm->hback_porch * dsi_tmp_buf_bpp - 10);
> > +               horizontal_backporch_byte = vm->hback_porch * dsi_tmp_buf_bpp;
> >         else
> > -               horizontal_backporch_byte = ((vm->hback_porch + vm->hsync_len) *
> > -                       dsi_tmp_buf_bpp - 10);
> > +               horizontal_backporch_byte = (vm->hback_porch + vm->hsync_len) *
> > +                                           dsi_tmp_buf_bpp;
> >
> >         data_phy_cycles = 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_bpp >
> > --
> > 2.12.5
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