Hi Taniya, Thanks, that is a clear answer and I will drop the clock-side shape.
Taking your two points at face value: - the resets belong to the display side, not to dispcc probe; - resetting the whole block after the PLLs are configured will flicker. So the RFC as posted is withdrawn. I will not resend it in that form. Where I think the replacement lands, and where I would like your opinion before spending time on it: The reset already exists on the display side. msm_mdss_reset() in drivers/gpu/drm/msm/msm_mdss.c asserts the mdss reset, sleeps 20 ms and deasserts it, and sm8750.dtsi already points that reset at DISP_CC_MDSS_CORE_BCR. The "hold it for one frame" timing is not new either, that function carries the same comment upstream today. So the mechanism is there; my patch only moved it earlier, into dispcc probe. The reason I moved it is ordering. On this SoC mdss consumes dispcc clocks and MDSS_GDSC, so dispcc probes first and the dispcc PLLs are programmed inside disp_cc_sm8750_probe(). msm_mdss_reset() then runs after that, so resetting there would take down PLLs that were just configured - which is the flicker you describe, and quite possibly the same failure I was trying to avoid in the first place. So my open question is narrower than the original RFC: given that ordering, where should a board that is handed over with a live display block put the reset? Three shapes I can see: 1. keep only the single CORE_BCR reset that DT already describes, and let the clock framework reprogram the PLLs after it; 2. drop the block reset entirely and do a per-encoder reset in the DPU/DSI enable path, so the PLL section is never touched; 3. leave it to the bootloader - the vendor loader has a DisableDisplayHW knob for exactly this - and carry nothing in the kernel. I am not asking you to design it. I would just like to know which of those three you would not reject outright, so I do not spend a cycle on the wrong one. If the answer is "none of them, this is a bootloader problem", that is a useful answer too and I will write it up that way. No date attached - this is a background item for me, and I would rather come back with measurements than with a schedule. Thanks, Qianhui Xu
