Hey all, hoping to draw attention to a pretty frustrating driver issue on Linux. Display power management is unreliable with AMD GPUs and certain HDMI displays on Linux. It seems as though monitors with automatic input switching/polling triggers a hotplug event, so that when the monitor polls its inputs before going to hardware sleep, it wakes the system back up. This results in an endless sleep/wake loop.
I was able to partially rectify the problem by configuring ACPI to ignore hotplug events from the GPU, but that revealed a different and possibly related issue. Instead of endlessly sleeping and waking, the monitor just wakes back up and displays a blank screen endlessly.
I'm running Red Hat Linux 9 on an ASUS PN51, with an AMD 5700U APU. This issue occurs regardless of whether I've installed AMD's driver, or I'm using the one provided with the kernel. People are reporting similar issues with a wide variety of AMD chipsets and Linux distros at the bug report below.
There's a bug report here, which is several years old. Not sure whether it's the right place for a report like this, so maybe someone here knows how to get some traction on it.