[Intel-gfx] [PATCH v2 1/2] PCI / PM: Add needs_resume flag to avoid suspend complete optimization

[Rafael J. Wysocki]

On Monday, April 24, 2017 10:42:42 PM Lukas Wunner wrote:
> On Mon, Apr 24, 2017 at 10:02:30PM +0200, Lukas Wunner wrote:
> > On Mon, Apr 24, 2017 at 05:27:42PM +0300, Imre Deak wrote:
> > > Some drivers - like i915 - may not support the system suspend direct
> > > complete optimization due to differences in their runtime and system
> > > suspend sequence. Add a flag that when set resumes the device before
> > > calling the driver's system suspend handlers which effectively disables
> > > the optimization.
> > 
> > FWIW, there are at least two alternative solutions to this problem which
> > do not require changes to the PCI core:
> > 
> > (1) Add a ->prepare hook to i915_pm_ops which calls pm_runtime_get_sync()
> >     and a ->complete hook which calls pm_runtime_put().
> 
> Thinking a bit more about this, it's even simpler:  The PM core acquires
> a runtime PM ref in device_prepare() and releases it in device_complete(),
> so it's sufficient to just call pm_runtime_resume() in a ->prepare hook
> that's newly added to i915.  No ->complete hook necessary.  Tentative
> patch below, based on drm-intel-fixes, would replace both of your patches.

Calling it in ->prepare() means that everybody is now waiting for you to resume.

Not quite optimal IMO.

Thanks,
Rafael