Created attachment 69076
dmesg after reproducing it with drm.debug=0xe
This commit causes a lenovo v490u to have a black screen after booting
It's working properly in 3.7, but 3.6 is broken without reverting that, and that commit was backported to the stable kernels which are now broken also. Suspending/resuming the machine after booting brings the display back up.
(working with revert)
[ 12.179335] [drm:intel_choose_pipe_bpp_dither], clamping display bpc (was -1) to eDP (6)
[ 12.179337] [drm:intel_choose_pipe_bpp_dither], setting pipe bpc to 8 (max display bpc 6)
[ 14.264823] [drm:intel_choose_pipe_bpp_dither], setting pipe bpc to 8 (max display bpc 8)