[Intel-gfx] [PATCH] i915: sanity check IER at wait_request time

[Dan Nicholson]

On Tue, May 5, 2009 at 4:03 PM, Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
> 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.

Just a note that the most recent pm-utils won't call vbetool and
friends if it detects that KMS is on.

http://cgit.freedesktop.org/pm-utils/commit/?id=a79d1630

Detection of KMS hinges on existence of
/sys/class/drm/card0/device/graphics/fb0, which came from Kristian.
But that just covers suspend/resume. I don't know why vbetool would be
getting called during boot.

--
Dan