Bugzilla https://bugzilla.kernel.org/show_bug.cgi?id=105331
received a potential fix that was backported to stable. While that patch itself is correct for treating DP video sinks with "unknown color depth", it uncovered some lack in our general EDID 1.3 handling, and in how we treat DP->DVI/VGA, causing the fall back of Intel DP to 6 bpc / 18 bpp in cases where it shouldn't fall back. That leads to unhappy neuroscience/medical users of Intel gpus which need their DP->DVI or DP->VGA display devices to operate at at least 8 bpc without dithering.
The following three patches try to improve our EDID handling and Intel DP to try harder to detect the proper bpc to avoid these regressions for DP-DVI and DP-VGA. The third patch tries to fix FDO bug 105331 without causing general unhappiness of other users.
thanks, -mario