https://bugs.freedesktop.org/show_bug.cgi?id=102008
--- Comment #2 from bartos.petr@gmail.com --- So I have some partial results.
First problem I've encoutered is that I had to use patch from https://bugs.freedesktop.org/show_bug.cgi?id=101774 in order to be able to build mesa between 7250cbafb90271579a1d07160498e902996cbc97 and 5ffe0c9e1be0257de1943135244419cbc86a6d84 so I hope it does not affect these results.
Second problem I found is that problem is connected with using modesetting DDX drivers, and between working and non-working commits is some problem causing segfault with modesetting drivers (X do not start). So I have tested not only particular commits, but also DDX driver combinations:
intel - IGPU, DRI3, SNA accel radeon - DGPU, DRI3, glamor accel modesetting - both, default settings
So far I managed to find this (I have not finished bisecting yet, so these commits are ones I've found so far):
f33d8af7aa354d00808f8bfd55028c396c706635 intel, radeon - OK intel, modesetting - OK modesetting, radeon - ERROR modesetting, modesetting - ERROR
81fb1547772d42c527318837d4207ecdb6899e5d intel, radeon - OK intel, modesetting - SEGFAULT modesetting, radeon - SEGFAULT modesetting, modesetting - SEGFAULT
3645268748c44825ce8d37bf03f684731eb2652a intel, radeon - OK intel, modesetting - SEGFAULT modesetting, radeon - SEGFAULT modesetting, modesetting - SEGFAULT
84ed8b67c56b323cd834d463151e1a3c0430c53e intel, radeon - OK intel, modesetting - OK modesetting, radeon - OK modesetting, modesetting - OK
So it seems between somewhere between 84ed8b67c56b323cd834d463151e1a3c0430c53e and f33d8af7aa354d00808f8bfd55028c396c706635 (https://cgit.freedesktop.org/mesa/mesa/log/?qt=range&q=84ed8b67c56b323cd...) modesetting driver started to segfault which was fixed, but this fix probably also caused problem which I have reported.
It also seems there is no problem when using only intel+radeon DDX drivers.