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SubjectRe: [PATCH v5 1/1] drm/mediatek: dsi: fix scrolling of panel with small hfp or hbp
On Tue, Oct 13, 2020 at 6:06 PM 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 | 65 +++++++++++++++-----------------------
> 1 file changed, 25 insertions(+), 40 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index 80b7a082e874..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;
> @@ -466,50 +467,34 @@ static void mtk_dsi_config_vdo_timing(struct mtk_dsi *dsi)
> horizontal_sync_active_byte = (vm->hsync_len * dsi_tmp_buf_bpp - 10);
>
> if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE)
> - horizontal_backporch_byte = vm->hback_porch * dsi_tmp_buf_bpp;
> + horizontal_backporch_byte =
> + (vm->hback_porch * dsi_tmp_buf_bpp - 10);

These parentheses are not required, but it might be a little clearer to write:
(vm->hback_porch * dsi_tmp_buf_bpp) - 10;

> else
> - horizontal_backporch_byte = (vm->hback_porch + vm->hsync_len) *
> - dsi_tmp_buf_bpp;
> + horizontal_backporch_byte = ((vm->hback_porch + vm->hsync_len) *
> + dsi_tmp_buf_bpp - 10);

ditto:
((vm->hback_porch + vm->hsync_len) * dsi_tmp_buf_bpp) - 10;

But then, _maybe_ it's clearer to drop this hunk and just add this
below the if/else:

horizontal_backporch_byte -= 10;

>
> 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;
> - }
> + timing->da_hs_zero + timing->da_hs_exit + 3;

(for reference, apart from this `+ 3`, there is no functional change
in this hunk: this just moves delta outside of the if/else block,
which is a good idea for readability)

> +
> + 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);
> --
> 2.12.5
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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