Public bug reported: 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. ** Affects: linux (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. 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: New 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. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1770836/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
