Created attachment 127405 [details] Kernel log extract, showing the unblanking failure. Setup: RX 470 with two monitors attached – one via DVI-and one via HDMI. (Both are AOC monitors.) * Ensure that outputs are blanked (via xset, time-out or similar). * Switch off the monitors. * Unblank the outputs. * Switch on the monitors. Invariably, in this situation, the DVI-connected monitor is unblanked and displaying what it should be, but the HDMI-connected monitor is receiving no signal (or at least nothing to display) and is therefore displaying nothing. The HDMI-connected monitor can be restored by using xrandr to change mode or by blanking and unblanking – so long as it's switched on while doing so.
JFYI: A similar, but more dramatic symptom that may be related I reported in https://bugs.freedesktop.org/show_bug.cgi?id=102323
Currently running amd-staging-drm-next 0313e8bfbbdd. The behaviour is now improved, though is still regressed vs. mainline. Unblanking works. If I allow the problem monitor to display “no signal”, it becomes effectively disconnected, and becomes reconnected (as if physically freshly connected) on unblanking.
Created attachment 133671 [details] Kernel log showing normal blank & unblank.
Created attachment 133673 [details] Kernel log showing blanking & as-if-reconnected unblanking.
JFYI: A patch attached to report https://bugs.freedesktop.org/show_bug.cgi?id=102323 provided some improved behaviour regarding switched-off HDMI displays.
That patch makes no difference to this problem.
Seems to be working properly with current amd-staging-drm-next (43dd6fde5df4).
Broken (same symptoms, though the kernel log looks a little different) with drm-next-4.15-dc (fbf0c14dd75) (merged with 4.13.4).
Created attachment 134594 [details] Apparent EDID errors HDMI monitor set to 1920×1080, but on unblanking gets set to 1152×864. This is the second time that I've seen this. Both times it's happened on the first unblanking after boot; both times, using drm-next-4.15-dc.
Created attachment 139325 [details] Good EDID output (4.17-rc3 + DC)
Created attachment 139326 [details] Bad EDID output (4.17-rc3 + DC) Once this happens (after VESA blanking long enough for the problem monitor to fully go to sleep), it persists until reboot.
I remember this having this issue and found that switching to the console (CTRL-ALT-F1) and then back to X once or twice woke the monitor.
EDID problems are gone in drm-next-4.18. However, the disconnection issue remains.
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