Created attachment 136624 [details]
GPU crash dump from /sys/class/drm/card0/error as requested

I'm filing this as a new bug in accordance with instructions found in the journal from the kernel following a GPU hang.

Symptoms: GPU hangs sometimes when running on battery. Hangs occur only when the laptop is left awake without interaction for a little bit (e.g. while making a cup of tea or popping to the loo). Hangs do not occur predictably, however, and these conditions mostly result in no hang. When a hang does occur, the machine is unresponsive on return and cannot be put to sleep or woken etc. Screen is blank/black. Following hard reset, messages such as the following can be found in the journal:

Ion 09 03:17:16 MyComputer kernel: [drm] GPU HANG: ecode 9:0:0xfffffffe, reason: Hang on rcs0, action: reset
Ion 09 03:17:16 MyComputer kernel: [drm] GPU hangs can indicate a bug anywhere in the entire gfx stack, including userspace.
Ion 09 03:17:16 MyComputer kernel: [drm] Please file a _new_ bug report on bugs.freedesktop.org against DRI -> DRM/Intel
Ion 09 03:17:16 MyComputer kernel: [drm] drm/i915 developers can then reassign to the right component if it's not a kernel issue.
Ion 09 03:17:16 MyComputer kernel: [drm] The gpu crash dump is required to analyze gpu hangs, so please always attach it.
Ion 09 03:17:16 MyComputer kernel: [drm] GPU crash dump saved to /sys/class/drm/card0/error
Ion 09 03:17:16 MyComputer kernel: i915 0000:00:02.0: Resetting rcs0 after gpu hang

The last is repeated many times. As the crash dump does not typically survive a reboot, a dump was collected using

dmesg -w | awk '/GPU crash dump saved to \/sys\/class\/drm\/card0\/error/ {system("cat /sys/class/drm/card0/error | bzip2 > error.bz2")}'

as suggested at https://bbs.archlinux.org/viewtopic.php?pid=1753566#p1753566.

Since the dump is not especially large, I'm attaching the decompressed version. 

I would be happy to provide further information on request, provided I can figure out how to do whatever would be helpful.