Hotplugging DP1.2 monitor(s) causes machine to hang waiting for page flip

Submitted by Robert Straw

Assigned to Default DRI bug account

Description

Created attachment 142774
dmesg: DRM call stack

Greetings,

I am using kernel 4.19.8, I have two 4K panels which have DP1.2 inputs as well as an AMD RX560 GPU[1]. I am experiencing an issue where my machine softlocks when they are disconnected & subsequently reconnected. If the monitors are power-cycled ,or the DP cable is hotplugged, my kernel log slowly accumulates messages like "ERROR [PLANE:36:plane-0] flip_done timed out" meanwhile my graphical environment hangs, waiting for the pageflip which never successfully happens. One of my monitors also happens be HDMI2.0 capable, and when connected via HDMI that monitor does not lock up the machine in this way, so I believe this issue to be DisplayPort specific.

Attached is a dmesg from a recent session exhibiting such a softlock, the relevant portions are near the end. All my softlocks have RIP: 0010:prepare_flip_isr+0x5f/0x70 [amdgpu] in common. I will note that the driver does seem to at least partially initialize the monitors upon reconnection, as they do not display "no signal" nor enter sleep mode.

[1]: Advanced Micro Devices, Inc. [AMD/ATI] Baffin [Radeon RX 550 640SP / RX 560/560X] [1002:67ff] (rev cf)

Attachment 142774, "dmesg: DRM call stack":
dmesg-reset-asus.txt