[Intel-gfx] [PATCH v2 2/2] drm/i915/skl: Increase PCODE CDCLK change notify timeout

[Chris Wilson]

On Fri, Nov 25, 2016 at 01:30:38PM +0200, Ville Syrjälä wrote:
> On Fri, Nov 25, 2016 at 12:57:01PM +0200, Imre Deak wrote:
> > commit 848496e5902833600f7992f4faa82dc1546051ba
> > Author: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > Date:   Wed Jul 13 16:32:03 2016 +0300
> > 
> >     drm/i915: Wait up to 3ms for the pcu to ack the cdclk change request on SKL
> > 
> > increased the timeout to match the spec, but we still see a timeout on
> > at least one SKL. A CDCLK change request following the failed one will
> > succeed nevertheless, so let's try to increase the timeout to 10ms.
> > 
> > v2:
> > - Use 1ms poll period instead of 10us. (Chris)
> 
> I'm not sure that's what we want. IIRC the spec says no delay between
> attempts, so I'm not sure this isn't just going to make it more likely
> to fail.

Hmm. We're going to be scheduled away eventually, unless we steal the
cpu for 10ms. To be strict to the spec we would need

	preempt_disable();
	ret = wait_for_atomic(pcu_ready(), 10);
	preempt_enable();

	return ret;

-- 
Chris Wilson, Intel Open Source Technology Centre