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With 4.18 rc kernel stop working video output on AMD GPU Vega 56

Submitted by Mikhail Gavrilov @Mikhail

Assigned to Default DRI bug account

Link to original bug (#107082)

Description

  • when monitor plugged via display port after boot I see blank screen, but system react on Ctrl-Alt-Delete and I could connect via ssh and reboot system by init 6 command.
  • when monitor plugged via HDMI was system hang during boot.

More detail provided in downstream report: https://bugzilla.redhat.com/show_bug.cgi?id=1592110

Also I bisecting kernel for investigating problem:

$ git bisect log
# bad: [4c5e8fc62d6a63065eeae80808c498d1dcfea4f4] Merge tag 'linux-kselftest-4.18-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest
# good: [2837461dbe6f4a9acc0d86f88825888109211c99] Merge tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi
git bisect start '4c5e8fc62d6a63065eeae80808c498d1dcfea4f4' '2837461dbe6f4a9acc0d86f88825888109211c99'
# good: [b5d903c2d656e9bc54bc76554a477d796a63120d] Merge branch 'akpm' (patches from Andrew)
git bisect good b5d903c2d656e9bc54bc76554a477d796a63120d
# bad: [a0b2ac29415bb44d1c212184c1385a1abe68db5c] drm/amdgpu: fix the missed vcn fw version report
git bisect bad a0b2ac29415bb44d1c212184c1385a1abe68db5c
# bad: [0b19fdc45feffd7569c081fe32a258df3c8ebb9b] drm/amd/display: fix dscl_manual_ratio_init
git bisect bad 0b19fdc45feffd7569c081fe32a258df3c8ebb9b
# bad: [4c6530fd66399182d0332c5ed821ea473bdcd7c3] drm/amdgpu: remove unnecessary scheduler entity for VCN
git bisect bad 4c6530fd66399182d0332c5ed821ea473bdcd7c3
# bad: [10dd2b865393bb45526ca342fe69207341f89fd5] drm/amd/display: Fix wrong latency assignment for VEGA clock levels
git bisect bad 10dd2b865393bb45526ca342fe69207341f89fd5
# bad: [adea72c5046f7faffff969ece04c3f31e669edf4] drm/amdgpu: vcn_v1_0_is_idle() can be static
git bisect bad adea72c5046f7faffff969ece04c3f31e669edf4
# bad: [bfdec234047889f4f6af1ec45c7c502a4405b3fb] drm/amd/display: Implement dm_pp_get_clock_levels_by_type_with_latency
git bisect bad bfdec234047889f4f6af1ec45c7c502a4405b3fb
# first bad commit: [bfdec234047889f4f6af1ec45c7c502a4405b3fb] drm/amd/display: Implement dm_pp_get_clock_levels_by_type_with_latency