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SubjectRe: [v3 PATCH] drm/mediatek: dsi: fix scrolling of panel with small hfp or hbp
Hi Jitao, 

On Thu, 17 Sep 2020 11:30:09 +0800
Jitao Shi <jitao.shi@mediatek.com> wrote:

> Replace horizontal_backporch_byte with vm->hback_porch * bpp to aovid
> flowing judgement negative number.
>
> if ((vm->hfront_porch * dsi_tmp_buf_bpp + horizontal_backporch_byte) >
> data_phy_cycles * dsi->lanes + delta)
>
> Signed-off-by: Jitao Shi <jitao.shi@mediatek.com>
> ---
> drivers/gpu/drm/mediatek/mtk_dsi.c | 54
> ++++++++++++++------------------------ 1 file changed, 19
> insertions(+), 35 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c
> b/drivers/gpu/drm/mediatek/mtk_dsi.c index 16fd99dcdacf..ddddf69ebeaf
> 100644 --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -445,6 +445,7 @@ static void mtk_dsi_config_vdo_timing(struct
> mtk_dsi *dsi) u32 horizontal_backporch_byte;
> u32 horizontal_frontporch_byte;
> u32 dsi_tmp_buf_bpp, data_phy_cycles;
> + u32 delta;
> struct mtk_phy_timing *timing = &dsi->phy_timing;
>
> struct videomode *vm = &dsi->vm;
> @@ -475,42 +476,25 @@ 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 +
> 3;
> - 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; +
> + if ((vm->hfront_porch * dsi_tmp_buf_bpp +
> horizontal_backporch_byte) >
> + data_phy_cycles * dsi->lanes + delta) {
> + horizontal_frontporch_byte =
> + vm->hfront_porch * dsi_tmp_buf_bpp -
> + (data_phy_cycles * dsi->lanes + delta) *
> + vm->hfront_porch /
> + (vm->hfront_porch + vm->hback_porch);
> +
> + horizontal_backporch_byte =
> + horizontal_backporch_byte -
> + (data_phy_cycles * dsi->lanes + delta) *
> + vm->hback_porch /
> + (vm->hfront_porch + vm->hback_porch);
> } 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");
> + horizontal_frontporch_byte = vm->hfront_porch *
> + dsi_tmp_buf_bpp;
> }
>
> writel(horizontal_sync_active_byte, dsi->regs + DSI_HSA_WC);

Can you explain how this patch is relevant to
https://patchwork.kernel.org/patch/11718191/? It was sent out on
17/Sept while the v2 was merged before that.

As the v2 patch (https://patchwork.kernel.org/patch/11718191/) breaks
HDMI (eDP) on my Chromebook Elm (starting from 5.9-rc6), I'm guessing
that that was a bad patch, and should be reverted? Instead, this v3
should be applied? Is this correct?

If so, can you kindly send a new patch which reverts v2 and applies
this one, as application of this patch on rc7 fails.

Thanks,
Bilal

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