[Intel-gfx] [PATCH v2 22/22] drm/i915/audio: Resume HSW/BDW HDA controller around ELD access

[Ville Syrjälä]

On Wed, Oct 12, 2022 at 05:24:56PM +0300, Ville Syrjälä wrote:
> On Wed, Oct 12, 2022 at 01:49:36PM +0300, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > 
> > On HSW/BDW the hardware ELD buffer does not work if the controller
> > is suspended. I'm not 100% which thing in there is needed to make it
> > work (at least just forcing the controller into D0 with setpci is
> > not enough). But a full runtime resume seems to do the trick here
> > at least, and so far it looks like this doesn't even deadlock or
> > anything.
> 
> So this apparently works for evrything else except module reload,
> where the ELD buffer isn't ready by the time we do the first modeset.
> Strangely the same thing works fine at boot time when we first load
> the drivers. Not sure what the difference is here.

I think the difference was that during boot I had an enabled displays
so we never turned off the power well. But during reload the power
well gets disabled briefly and some state gets lost.

-- 
Ville Syrjälä
Intel