[Intel-gfx] [PATCH] drm/i915: Prevent the system suspend complete optimization

[Chris Wilson]

On Tue, Apr 11, 2017 at 08:09:17PM +0300, Imre Deak wrote:
> On Tue, Apr 11, 2017 at 05:54:07PM +0100, Chris Wilson wrote:
> > On Tue, Apr 11, 2017 at 07:12:35PM +0300, Imre Deak wrote:
> > > +static int i915_pm_prepare(struct device *kdev)
> > > +{
> > > +	/*
> > > +	 * Get a reference to disable the direct complete optimization. This
> > > +	 * is needed, since we have a suspend sequence specific to system
> > > +	 * suspend (that is different from runtime suspend) and because we
> > > +	 * need to provide power to the sound driver while its system suspend
> > > +	 * handler is running. This is not possible with the optimization in
> > > +	 * effect, when the i915 runtime PM is disabled for the whole duration
> > > +	 * of the suspend sequence if the device was already runtime
> > > +	 * suspended at the beginning of the sequence. In this case the i915
> > > +	 * suspend/resume hooks would be also skipped (besides its prepare and
> > > +	 * complete hooks).
> > > +	 */
> > > +	intel_runtime_pm_get(kdev_to_i915(kdev));
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static void i915_pm_complete(struct device *kdev)
> > > +{
> > > +	/* Put the ref taken in the prepare step. */
> > > +	intel_runtime_pm_put(kdev_to_i915(kdev));
> > 
> > Do we always call i915_pm_complete() if any of the post-prepare suspend
> > steps fail? Otherwise, it looks very sensible from our pov.
> 
> Yes, it's called even in the failure case (for S3 for example
> suspend_devices_and_enter()->Recover_platform:->Resume_devices:->
> dpm_resume_end()->dpm_complete()).

>From our pov, this is ok.

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>

And we can apply this whilst we investigate whether this is the best
approach to avoiding the suspend optimization.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre