Regression: DP outputs out of sync on dual-DP tiled 5k screen
Submitted by Tomas Bzatek
Assigned to Default DRI bug account
With kernel 5.1.1 I get corrupted image on my Dell UP2715K screen (again). The symptomps are similar to the ones in bug 98461 (see also attachment 127570). In my theory this is caused by the two DisplayPort outputs not being in sync - the screen needs both tiles to be in sync (i.e. scanlines to match) to make a composite final image.
The Dell UP2715K monitor has two DP 1.2 inputs, two tiles expecting 2560x2880@60Hz modes (as exposed in EDID/DisplayInfo data). Connected to Radeon Pro WX2100 (Polaris 12).
This used to be actually working reliably in kernel 4.20.0, yesterday I fired up kernel 5.1.1 and only got garbage on my screen. Also tested drm-tip kernel that includes drm-next-5.2 branch from the agd5f repo (https://patchwork.freedesktop.org/patch/304430/) - same issue.
I haven't got time to bisect the change yet, I was hoping you could point me to a possible commit that broke this. By any chance, do you AMD guys have a 5k tiled screen inhouse for testing?