This is a note to let you know that I've just added the patch titled drm/mediatek: dsi: Reduce the time of dsi from LP11 to sending cmd to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: drm-mediatek-dsi-reduce-the-time-of-dsi-from-lp11-to.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 653906ce310b056f3b8d0de8acffc3f0aad78639 Author: Xinlei Lee <xinlei.lee@xxxxxxxxxxxx> Date: Tue Jan 10 13:54:51 2023 +0800 drm/mediatek: dsi: Reduce the time of dsi from LP11 to sending cmd [ Upstream commit 91aeaed2c1147e3b1157dc084d23f190856a6c23 ] According to Figure 16 Turnaround Procedure on page 36 in [1], you can see the status of LP-00 -> LP10 -> LP11. This state can correspond to the state of DSI from LP00 -> LP11 in mtk_dsi_lane_ready function in mtk_dsi.c. LP-00 -> LP10 -> LP11 takes about 2*TLPX time (refer to [1] page 51 to see that TLPX is 50ns) The delay at the end of the mtk_dsi_lane_ready function should be greater than the 2*TLPX specified by the DSI spec, and less than the time specified by the DSI_RX (generally 6ms to 40ms), to avoid problems caused by the RX specification [1]:mipi_D-PHY_specification_v1-1 Fixes: 39e8d062b03c ("drm/mediatek: Keep dsi as LP00 before dcs cmds transfer") Signed-off-by: Xinlei Lee <xinlei.lee@xxxxxxxxxxxx> Acked-by: Sam Ravnborg <sam@xxxxxxxxxxxx> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx> Link: https://patchwork.kernel.org/project/linux-mediatek/patch/1673330093-6771-2-git-send-email-xinlei.lee@xxxxxxxxxxxx/ Signed-off-by: Chun-Kuang Hu <chunkuang.hu@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c index a6d28533f1b12..98b1204c92906 100644 --- a/drivers/gpu/drm/mediatek/mtk_dsi.c +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c @@ -709,7 +709,7 @@ static void mtk_dsi_lane_ready(struct mtk_dsi *dsi) mtk_dsi_clk_ulp_mode_leave(dsi); mtk_dsi_lane0_ulp_mode_leave(dsi); mtk_dsi_clk_hs_mode(dsi, 0); - msleep(20); + usleep_range(1000, 3000); /* The reaction time after pulling up the mipi signal for dsi_rx */ } }