[Intel-gfx] [PATCH] drm/i915/gen4: Fix interrupt setup ordering

[Eric Anholt]

On Thu, 03 Jun 2010 17:31:22 -0400, Adam Jackson <ajax at redhat.com> wrote:
> On Thu, 2010-05-27 at 17:26 -0400, Adam Jackson wrote:
> > Unmask, then enable interrupts, then enable interrupt sources; matches
> > PCH ordering.  The old way (sources, enable, unmask) gives a window
> > during which interrupt conditions would appear in ISR but would never
> > reach IIR and thus never raise an IRQ.  Since interrupts only trigger
> > on rising edges in ISR, this would lead to conditions where (for
> > example) output hotplugging would never fire an interrupt because it
> > was already stuck on in ISR.
> > 
> > Also, since we know IIR and PIPExSTAT have been cleared during
> > irq_preinstall, don't clear them again during irq_postinstall, nothing
> > good can come of that.
> > 
> > Signed-off-by: Adam Jackson <ajax at redhat.com>
> 
> Just to follow up, I've tested this (combined with the already-merged
> VGA paranoia patch) on GM45.  Output hotplug still works and I'm no
> longer seeing stuck bits in ISR.

Thanks for the followup.  It really helps me to know what people have
tested on, and whether they were fixing a bug due to code inspection or
due to actually solving a problem they were hitting on hardware.
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