I have a LG 29UB55-B 21:9 monitor connected via DisplayPort to a Radeon R7 370 card after boot when xorg loads 99% of the time the monitor won't see a signal and goes to sleep once its woken back up by its power button it sees the normal screen at its native res of 2560x1080 I also see I assume the same problem if i change resolution down to 1920x1080 its fine but switch back to 2560x1080 and screen goes to sleep with no signal wake it back up and fine again at 2560 I see the below in dmesg: [ 6.400479] [drm:radeon_dp_link_train [radeon]] *ERROR* clock recovery reached max voltage [ 6.400523] [drm:radeon_dp_link_train [radeon]] *ERROR* clock recovery failed kernel is 4.14.4 currently it's been going on since I got the monitor I don't recall what version that was. xorg is on 1.19.5 amdgpu driver is 1.4.0 also tried the radeon driver and acts same haven't tried binary drivers no errors in xorg log
Please attach the full dmesg output. It might be worth trying a current 4.15-rc kernel with CONFIG_DRM_AMD_DC and CONFIG_DRM_AMD_DC_PRE_VEGA enabled.
Created attachment 136229 [details] dmesg log
Created attachment 136234 [details] dmesg with working screen here is dmesg on a boot that brought up monitor correctly version is: Linux ghoststar 4.15.0-rc3-mainline #1 SMP PREEMPT Sat Dec 16 15:27:26 PST 2017 x86_64 GNU/Linux I'm not sure if this version fixed it yet since a reboot onto 4.14.x worked also seems like cold boot might cause it to happen more often? ill try this a few more times over the coming week and see if it behaves and report back
4.15-rc3 still has the problem
Do you have a chance to try enabling the two config options Michel mentioned and see if this changes things? We have a new display driver in 4.15 (AMD_DC) that could very well make a difference here.
maybe it wasn't clear but I tested rc3 with those options and it still has the issue
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