[Intel-gfx] [PATCH 0/1] fix RC6p related regression on Sandy Bridge

[Sasa Dragic]

Hi all,

RC6p got re-enabled on Sandy Bridge over time, seemingly by accident
over time, causing graphical glitches and occasional GPU hangs on my
old ThinkPad T420, severity depending on kernel version.

It is a known issue, e.g.:
https://wiki.ubuntu.com/Kernel/PowerManagementRC6
https://www.yoctoproject.org/pipermail/yocto/2012-June/007164.html

It was originally disabled in commit 1c8ecf80fdee ("drm/i915: do not
enable RC6p on Sandy Bridge"), and subsequently re-enabled by
13c5a577b342 ("drm/i915/gt: Select the deepest available parking mode
for rc6"), which seems to focus only on Ivy Bridge.

This patch re-disables RC6p on Sandy Bridge.

I don't know if this issue is fixed otherwise, and I just have a faulty
hardware, but there are few unresolved Sandy Bridge issues floating on
the net, which could be related to this. When disabling RC6p graphics
works flawlessly, as it also works on 4.15 kernel without modifications.

I didn't want to clutter this mail with too much info, so feel free to
ask for details, links or to file bug report if necessary.

Thanks,
Sasa

Sasa Dragic (1):
  drm/i915: re-disable RC6p on Sandy Bridge

 drivers/gpu/drm/i915/i915_pci.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

-- 
2.37.2