[Intel-gfx] [regression?] i915 generating wakeups even when idle

[Chris Wilson]

On Tue, 7 Dec 2010 16:31:24 -0500, Andrew Lutomirski <luto at mit.edu> wrote:
> On Tue, Dec 7, 2010 at 4:03 PM, Andrew Lutomirski <luto at mit.edu> wrote:
> > Hi all-
> >
> > Somewhere between Fedora 13 (with 2.6.35, I think) and Fedora 14 +
> > 2.6.36.1, i915 started generating exactly 50 interrupts per second
> > (suspiciously equal to my refresh rate) when X is running.  I have the
> > Xorg driver 2.12.0 (specifically
> > xorg-x11-drv-intel-2.12.0-6.fc14.1.x86_64).  When I switch to a text
> > console but leave X running, the interrupts stop.
> >
> > Any ideas what to look at?
> 
> Quitting compiz fixes it.  Suspending compiz also fixes it.

So it is the vblank interrupt. The vblank interrupt is get alive for a few
seconds after the last use. If it keeps going, then either the system is
as idle as you believe or we lost track of the last user and forget to
switch off the interrupt.

drm.debug=0xf (echo 0xf > /sys/module/drm/parameters/debug) will have the
gory details of who/when triggers the vblank interrupt.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre