drm/i915: sanity check IER at wait_request time
We might sleep here anyway so I hope an extra uncached read is ok to
add.
In #20896 we found that vbetool clobbers the IER. In KMS mode this is
particularly bad since we don't set the interrupt regs late (in
EnterVT), so we'd fail to get *any* interrupts at all after X started
(since some distros have scripts that call vbetool at X startup
apparently).
So this patch checks IER at wait_request time, and re-enables
interrupts if it's been clobbered. In a proper config this check
should never be triggered.
This is really a distro issue, but having a sanity check is nice, as
long as it doesn't have a real performance hit.
Tested-by: Mateusz Kaduk <mateusz.kaduk@gmail.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
[anholt: Moved the check inside of the sleeping case to avoid perf cost]
Signed-off-by: Eric Anholt <eric@anholt.net>
1 file changed