Re: [PATCH 1/2] drm/i915: take a power domain ref only when needed during HDMI detect

Chris Wilson
2015-11-19T21:38:31Z

On Thu, Nov 19, 2015 at 11:01:49PM +0200, Imre Deak wrote:
> On Thu, 2015-11-19 at 20:51 +0000, Chris Wilson wrote:
> > On Thu, Nov 19, 2015 at 08:55:00PM +0200, Imre Deak wrote:
> > > Suggested by Ville.
> >
> > Do you mind explaining why this is done at the hdmi level and not the
> > gmbus level?
>
> To reduce the on/off toggling, since we don't have delayed power-off
> implemented for power wells. gmbus_xfer also takes a ref to account for
> accesses from the i2c device node. The solution would be to implement
> delayed power-off I guess.

As we chase ever finer grained wakelocks, yeah. Looking at the other
users of gmbus, they are the old platforms (dvo, sdvo, crt, lvds) so not
worth generalising the optimisation of holding the wakelock across the
entire i2c operation, I guess?
-Chris

--
Chris Wilson, Intel Open Source Technology Centre