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Status: New => Incomplete
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https://bugs.launchpad.net/bugs/1770836
Title:
amdgpu+xorg possibly marks displays as off while they wake from sleep
Status in linux package in Ubuntu:
Incomplete
Bug description:
Ubuntu 18.04, all the x, libdrm, kernel, etc. packages up to date.
KDE.
When waking the displays from sleep with 4.15 (amdgpu.dc=1) any
display not yet fully woken up seem to be reported as disconnected.
This happens both when waking the whole computer from sleep (systemctl
suspend) or just the displays themselves (due to me not touching
mouse+keyboard for a while).
Setup:
Radeon RX 560
Primary display: bottom right, displayport, on
Secondary display 1: left, hdmi, on
Secondary display 2: top right, dvi, off
Video of how it should work using 4.4.15 and amdgpu.dc=0:
https://www.youtube.com/watch?v=h7nMYbm5ZxU
Note how even though the left (secondary) display wakes up first, both
instantly display their proper desktops.
Video of how it works with the current default kernel (and 4.16.7 from
kernel-ppa/mainline): https://www.youtube.com/watch?v=VdVFNXPszSI
Note how when the left (secondary) display wakes up first, KDE decides that
this is probably the only display available, so tries to switch the primary
desktop to it, then a split second later the bottom right wakes up and KDE
knows *that* should be the primary according to the config, so it switches back.
My interpretation is that KDE thinks the bottom right display slowly
waking up is actually off, so it does the reasonable thing and uses
the other available one as primary.
One way or the other, that's not how it used to work in older kernels
(which defaulted to amdgpu.dc=0), so as far as I'm concerned it's a
regression.
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