Re: [Intel-gfx] [PATCH v2] drm/i915: move power domain init earlier during system resume

[Takashi Iwai <tiwai@suse.de>]

At Tue, 1 Apr 2014 22:26:20 +0200,
Daniel Vetter wrote:
> 
> On Tue, Apr 01, 2014 at 09:50:43PM +0300, Imre Deak wrote:
> > On Tue, 2014-04-01 at 19:48 +0200, Daniel Vetter wrote:
> > > On Tue, Apr 01, 2014 at 07:55:22PM +0300, Imre Deak wrote:
> > > > During resume the intel hda audio driver depends on the i915 driver
> > > > reinitializing the audio power domain. Since the order of calling the
> > > > i915 resume handler wrt. that of the audio driver is not guaranteed,
> > > > move the power domain reinitialization step to the resume_early
> > > > handler. This is guaranteed to run before the resume handler of any
> > > > other driver.
> > > >
> > > > The power domain initialization in turn requires us to enable the i915
> > > > pci device first, so move that part earlier too.
> > > >
> > > > Accordingly disabling of the i915 pci device should happen after the
> > > > audio suspend handler ran. So move the disabling later from the i915
> > > > resume handler to the resume_late handler.
> > > >
> > > > v2:
> > > > - move intel_uncore_sanitize/early_sanitize earlier too, so they don't
> > > >   get reordered wrt. intel_power_domains_init_hw()
> > > >
> > > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76152
> > > > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > >
> > > So this is kinda why we should have gone with something proper, like a new
> > > hdmi sink platform device created by i915 and registered as a driver by
> > > snd-hda. Then the power domains stuff in the device core should take care
> > > of these kinds of ordering issues. Or at least snd-hda can tell it that it
> > > needs to wait for the hdmi-sink power domain to go on first before it can
> > > resume, I'm not really fluent on the details here.
> > >
> > > And having a hdmi sink bus would allow us to throw all kinds of crap into
> > > a clearly-defined interface, e.g. eld handling, hdcp synchronization, hpd
> > > forwarding and all the other fun stuff.
> > >
> > > So not sure what I should do with this here now.
> >
> > Right, I'm not too happy about this solution either, so if anything it
> > could be considered only a stop-gap fix. What you suggest seems to be a
> > cleaner way but it'd require more time to investigate/implement at least
> > on my part (but I'm ok to put it on my TODO list).
> 
> We'd definitely need to discuss this with Takashi Iwai, since it would
> only really be useful if it's good enough to solve the general pile of
> sound/gfx coordination issues we have with hdmi. Adding him and alsa-dev.

Yep, having a dedicated channel (hdmi sink bus or whatever) would be
definitely a better way to go.  OTOH, I agree that Imre's patch is
needed for the upcoming kernel.  The former implementation can't be
finished so quickly for 3.15.

I thought Mengdong started looking at (or working on) this, but
haven't heard the progress yet.  Mengdong, any news?


thanks,

Takashi