On Ubuntu Bionic with kernels 4.15 and above, RX480 Displayport outputs don't work (dmesg reports "not connected")

Submitted by Pixie

Assigned to Default DRI bug account

Link to original bug (#106718)

Description

Anything from at least 4.15 up to 4.17-rc1 under Bionic makes the Displayport connections fail to even detect a display, while anything 4.14.x works and detects it perfectly.

Is the PCI ROM error related? Is this a duplicate? I can provide xorg logs later today.

added AMDgpu bugzilla labels

Michel Dänzer @daenzer said:

Please attach the dmesg output as well as the Xorg log file.

Pixie said:

Alright. Will do in a couple hours, when booted on newer kernels. Currently booted on an old one, probably good to include it as well for comparison's sake. Google turned up nothing on this issue either, so I came here.

Would a Displayport to DVI converter have anything to do with recent changes?

Alex Deucher @agd5f said:

Can you narrow down the regression or better yet bisect?

Pixie said:

If instructed how, I would definitely be willing to bisect.

Power went out, fell asleep, no xorg logs during the day. Sorry for the delay, a working log/dmesg combo on 4.14.35 coming up shortly, for reference.

This breaks on any kernel 4.15 and above, by the way. Decided to report it against whatever is present in 4.17, since the issue still persists there.

And if I can get rc4 to install, I'll test that and provide the logs from that.

Pixie uploaded an attachment:

Attachment 139875, "dmesg log on a working setup (kernel 4.14.35, latest stable mesa)":
dmesg.txt

Pixie uploaded an attachment:

Attachment 139876, "Xorg log on the same functional 4.14.35 setup.":
xorglog.txt

Pixie said:

Logs from working software submitted. Booting promptly into a newer kernel and salvaging logs from there.

Pixie said:

Nope, fell flat on its face. rc1 logs coming shortly.

Pixie uploaded an attachment:

Attachment 139877, "dmesg from a broken 4.17-rc1 setup; look here for the errors":
brokendmesg.txt

Pixie uploaded an attachment:

The broken Xorg log doesn't even seem to acknowledge the monitor exists through a quick grep.

Attachment 139878, "Xorg log on the broken 4.17-rc1 setup":
brokenxorglog.txt

Pixie said:

Seems somewhere between what looks like versions 3.19 and 3.25.

Gonna guess 4.15 has an earlier version; gonna fetch logs from that shortly.

Pixie said:

Seems like I had the right idea.

4.15 runs amdgpu 3.23. May install a Mesa git version from a PPA after this to check.

Really want the new kernels, so I'm probably gonna do that right away after posting the two logs.

Pixie uploaded an attachment:

Attachment 139879, "Broken dmesg on 4.15":
brokendmesg-4.15.txt

Pixie uploaded an attachment:

Attachment 139880, "Broken Xorg log on 4.15":
brokenxorglog-4.15.txt

Pixie said:

That Git install doesn't seem to have changed anything visible. Doesn't show in logs either, which is weird.

Pixie said:

Running glxgears gives me a GL version of 3.1 Mesa 18.2.0-devel, that the one I'm looking for?

Michel Dänzer @daenzer said:

Does amdgpu.dc=0 on the kernel command line work around the problem?

Pixie said:

Where would I enter that?

Alex Deucher @agd5f said:

on the kernel command line in grub.