From d19faa0dcc6abd35ed67084d8e31590a243f77c0 Mon Sep 17 00:00:00 2001 From: Konrad Dybcio Date: Tue, 10 Mar 2026 14:20:25 +0100 Subject: drm/msm/mdss: Add a TODO for better managing the MDSS clock power state There's a small window where the MDP clock could be set to a high rate (say, from the bootloader) without a corresponding RPM(H)PD vote to back it up. This is normally not an issue, but could be, if rmmod fails to shut down the display driver cleanly, and the module is inserted again, or when the providers' .sync_state has timed out. Mark a TODO to fix it one day. Linking the relevant discussion below. Link: https://lore.kernel.org/linux-arm-msm/d5c4eed5-bd87-4156-b178-2d78140ec8a9@oss.qualcomm.com/ Signed-off-by: Konrad Dybcio Reviewed-by: Dmitry Baryshkov Patchwork: https://patchwork.freedesktop.org/patch/710572/ Link: https://lore.kernel.org/r/20260310-topic-mdss_power_todo-v1-1-59457b8b7486@oss.qualcomm.com Signed-off-by: Dmitry Baryshkov --- drivers/gpu/drm/msm/msm_mdss.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/gpu/drm/msm/msm_mdss.c b/drivers/gpu/drm/msm/msm_mdss.c index a86776425f26..90c3fa0681a0 100644 --- a/drivers/gpu/drm/msm/msm_mdss.c +++ b/drivers/gpu/drm/msm/msm_mdss.c @@ -262,6 +262,14 @@ static int msm_mdss_enable(struct msm_mdss *msm_mdss) icc_set_bw(msm_mdss->reg_bus_path, 0, msm_mdss->reg_bus_bw); + /* + * TODO: + * Previous users (e.g. the bootloader) may have left this clock at a high rate, which + * would remain set, as prepare_enable() doesn't reprogram it. This theoretically poses a + * risk of brownout, but realistically this path is almost exclusively excercised after the + * correct OPP has been set in one of the MDPn or DPU drivers, or during initial probe, + * before the RPM(H)PD sync_state is done. + */ ret = clk_bulk_prepare_enable(msm_mdss->num_clocks, msm_mdss->clocks); if (ret) { dev_err(msm_mdss->dev, "clock enable failed, ret:%d\n", ret); -- cgit v1.2.3