How can I fix a second monitor that won't wake after suspend on Linux?

[Ryan73]

I’ve been trying to get a dual monitor setup working on my Linux machine, but the second display just won’t wake up from sleep. I’m using a DisplayPort cable for the main screen and an HDMI connection for the other, and the system seems to detect both in the settings, but one stays black after the system suspends. I’m not sure if this is a driver issue or something with how the display manager handles waking up multiple outputs.

[Camila77]

I ran into the same thing last year. The system would wake up with the main DisplayPort screen fine, but the HDMI monitor stayed black after suspend. It looked like the HDMI output was detected but the signal never came up. I checked xrandr and it showed both outputs, just one never fully woke.

[JacobW]

On my box the culprit was the GPU driver. After a kernel or driver update the wake behavior loosened up, but it never felt reliable. It sometimes reinitialized the HDMI output and sometimes it stayed asleep. I also noticed some power management settings could put that output into a deeper sleep.

[Aubrey93]

I tried unplugging and re-plugging the HDMI cable after resume, switching the HDMI monitor to primary, and forcing a re-scan with xrandr, but nothing consistently fixed it. In the end I kept the HDMI as a clone for meetings, but the sleep wake still felt flaky.

[Kenneth.G]

Could the real issue be the display manager not rescanning outputs on wake?