Re: [PATCH] i915 suspend/resume_noirq instead of suspend_late/resume_early

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Apr 27, 2016 at 01:17:15PM -0700, Todd Brandt wrote:
> On Wed, 2016-04-27 at 22:31 +0300, Ville Syrjälä wrote:
> > On Wed, Apr 27, 2016 at 11:46:22AM -0700, Todd Brandt wrote:
> > >  I'd like to propose that we push the i915 suspend_late/resume_early code
> > >  into suspend_noirq/resume_noirq in order to reduce the total suspend time
> > >  by ~15ms. According to the comments, when i915_pm_suspend_late was first 
> > >  added to the kernel back in April 2014, it was done so to ensure that it
> > >  was called after the snd_hda_intel driver had finished its suspend.
> > > 
> > > The comments in i915_drv.c are here:
> > > 
> > >     /*
> > >      * We have a suspedn ordering issue with the snd-hda driver also
> > >      * requiring our device to be power up. Due to the lack of a
> > >      * parent/child relationship we currently solve this with an late
> > >      * suspend hook.
> > >      *
> > >      * FIXME: This should be solved with a special hdmi sink device or
> > >      * similar so that power domains can be employed.
> > >      */
> > > 
> > > I believe we could achieve the same ordering by simply pushing it to
> > > suspend/resume_noirq. Thus we can effectively eliminate the suspend_late
> > > and resume_early phases altogether in most simple systems. Does anyone see
> > > a problem with this?
> > > 
> > > analyzesuspend outputs for freeze/suspend/hibernate (WITHOUT PATCH):
> > > https://01org.github.io/suspendresume/i915/freeze-160422-155931-ivybridge-dev-late/
> > > https://01org.github.io/suspendresume/i915/suspend-160422-155735-ivybridge-dev-late/
> > > https://01org.github.io/suspendresume/i915/hibernate-160422-163915-ivybridge-dev-late/
> > > 
> > > analyzesuspend outputs for freeze/suspend/hibernate (WITH PATCH):
> > > https://01org.github.io/suspendresume/i915/freeze-160422-162811-ivybridge-dev-noirq/
> > > https://01org.github.io/suspendresume/i915/suspend-160422-162700-ivybridge-dev-noirq/
> > > https://01org.github.io/suspendresume/i915/hibernate-160422-162952-ivybridge-dev-noirq/
> > 
> > Hmm. Looking at those makes me confused. Why isn't the pci bus
> > .resume_noirq hook (pci_pm_resume_noirq()) waking up our pci device?
> > Instead our wakeup gets delayed until .resume_early for some reason.
> 
> Which timeline are you referring to? The "late" ones are the unaltered
> versions.

Referring to the current code, ie. the "late" timeline.

-- 
Ville Syrjälä
Intel OTC
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