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SubjectRe: [PATCH] drm/mediatek: dsi: Calculate horizontal_backporch_byte by itself
Hi CK, 

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

>
> Chun-Kuang Hu <chunkuang.hu@kernel.org> 於 2020年11月15日 週日
> 上午8:14寫道:
> >
> > 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 = &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

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