21.06.2021 14:43, Dmitry Osipenko пишет: > 21.06.2021 14:01, Thierry Reding пишет: >> On Mon, Jun 21, 2021 at 07:19:15AM +0300, Dmitry Osipenko wrote: >>> 07.06.2021 01:40, Dmitry Osipenko пишет: >>>> 01.06.2021 07:21, Dmitry Osipenko пишет: >>>>> This series adds memory bandwidth management to the NVIDIA Tegra DRM driver, >>>>> which is done using interconnect framework. It fixes display corruption that >>>>> happens due to insufficient memory bandwidth. >>>>> >>>>> Changelog: >>>>> >>>>> v18: - Moved total peak bandwidth from CRTC state to plane state and removed >>>>> dummy plane bandwidth state initialization from T186+ plane hub. This >>>>> was suggested by Thierry Reding to v17. >>>>> >>>>> - I haven't done anything about the cursor's plane bandwidth which >>>>> doesn't contribute to overlapping bandwidths for a small sized >>>>> window because it works okay as-is. >>>> >>>> Thierry, will you take these patches for 5.14? >>>> >>> >>> The display controller does _NOT_WORK_ properly without bandwidth >>> management. >> >> That's surprising. So either it has never worked before (which I think >> I'd know) or something has caused this regression recently. In the >> latter case we need to identify what that was and revert (or fix) it. > > The problem is caused by the support of dynamic memory frequency scaling > which does a good job at keeping memory in a low power state during idle > time. So display controller may not get enough bandwidth at the start of > scanout if it won't request BW beforehand. This problem existed for many > years on T124 and now T20/30 are also affected. The DC of T20 is the > least tolerant to memory bandwidth troubles. > > This problem is not critical, but it hurts user experience since high > resolution modes may not work at all and display output may become > distorted, requiring a DC reset. > >>> Can we get this patch into 5.14? What is the problem? >> >> There was not enough time to review and test this, so I didn't feel >> comfortable picking it up so close to the -rc6 cut-off. I plan to pick >> this up early in the v5.14 release cycle and target v5.15. > > Thank you for the explanation! It's not uncommon to forget about > patches, so the silence worries me. I hoped that both the dynamic freq > scaling and display BW support would be merged around the same time, but > apparently we got a disconnect here. > Reminder ping :)
