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

[Chun-Kuang Hu]

Hi, Bilal:

Please help to test this patch on your Chromebook elm, thanks.

Regards,
Chun-Kuang Hu

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
>