tree ce0c679c951a22b4e25f6d3eb447201aa9cab9f8
parent bc0588e482b1320d5739900b00a45033f5b587f4
author Angel Pons <th3fanbus@gmail.com> 1603309054 +0200
committer Nico Huber <nico.h@gmx.de> 1620329198 +0000

gfx gma skylake: Implement some workarounds

Without these workarounds, gfx_test will leave a WHL-U Librem Mini v1 in
a state where entering low-power states results in a hang. With these
workarounds, the system no longer locks up after running gfx_test. Looks
like the hang does not happen when coreboot runs libgfxinit.

Steps to reproduce the hang:
- Boot Linux without loading i915.
- Run gfx_test without the workarounds.
- After gfx_test exits and the machine enters a low-power state,
  it will lock up.

If something keeps the CPU from getting into low-power states (e.g.
`cat /dev/zero > /dev/null`), the machine will not lock up. However,
stopping the load task after gfx_test has run will result in a lock-up.

Change-Id: I4cd64cf4c1e702dc05709adc345a976a4e3c1ded
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/libgfxinit/+/46635
Reviewed-by: Nico Huber <nico.h@gmx.de>