Tentative fix/work-around for i915 GPU hangs

Some of you may have noticed the GPU hangs on Haswell Chromebooks in recent versions of you favourite distro. Well, a man called Fabrice G. (via email) furnished me with what appears to be a fix, this afternoon. It’s rather a long addition to the kernel cmdline, and I’m not sure if *absolutely* all of it is needed, but it certainly appears to be doing the job on my HP Chromebook 14, in CentOS 7, with a 3.17 kernel.

Simply add the following to GRUB_CMDLINE_LINUX in /etc/default/grub:

drm.debug=0 drm.vblankoffdelay=1 i915.semaphores=0 i915.modeset=1 i915.use_mmio_flip=1 i915.powersave=1 i915.enable_ips=1 i915.disable_power_well=1 i915.enable_hangcheck=1 i915.enable_cmd_parser=1 i915.fastboot=0 i915.enable_ppgtt=1 i915.reset=0 i915.lvds_use_ssc=0 i915.enable_psr=0

then run:

su -c "grub2-mkconfig > /boot/grub2/grub.cfg"

in CentOS/Fedora, or:

update-grub

in Debian/Ubuntu/etc

Enjoy!