[Intel-gfx] [PATCH] drm/i915: Don't sanitize frame start delay if the pipe is off

[Ville Syrjälä]

On Wed, Nov 15, 2017 at 08:17:21PM +0000, Chris Wilson wrote:
> Quoting Ville Syrjala (2017-11-15 20:04:42)
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > 
> > Avoid touching PIPECONF in intel_sanitize_crtc() unless the pipe is
> > actually on. Should cure some unclaimed register accesses.
> 
> While using crtc->active is consistent with other sanitization, is this
> really a fix for unclaimed register access?
> 
> We should be holding all the powerwells at this moment in bringing up
> the hw, right? So the only unclaimed access would be if the reg didn't
> exist. So are we looking at an invalid cpu_transcoder?

I was thinking we'd have dropped the power references already. But
I guess not. And that should definitely then give unclaimed register
accesses during driver init.

I think these fails are in the "pretend display gets clobbered by GPU
reset" path. And there we don't actually seem to grabbing the init power
reference, which could well explain this. 

Not sure we want to add the init power there either. Most of the readout
code now has the power domain handling in place, so maybe we're close
to being able to nuke the init power thing entirely?

-- 
Ville Syrjälä
Intel OTC