Re: [PATCH 1/1] drm/i915: Adding Gfx Clock, Wake and Gunit save/restore logic in PM suspend/resume paths.

[Daniel Vetter <daniel@ffwll.ch>]

Gn Fri, Aug 08, 2014 at 03:43:49PM +0200, Daniel Vetter wrote:
> On Fri, Aug 08, 2014 at 02:34:37PM +0300, Imre Deak wrote:
> > On Fri, 2014-08-08 at 15:54 +0530, Sagar Arun Kamble wrote:
> > > On Fri, 2014-08-08 at 11:15 +0200, Daniel Vetter wrote:
> > > > On Fri, Aug 08, 2014 at 02:29:38PM +0530, Sagar Arun Kamble wrote:
> > > > > On Fri, 2014-08-08 at 09:42 +0200, Daniel Vetter wrote:
> > > > > > On Fri, Aug 08, 2014 at 12:22:44PM +0530, Sagar Arun Kamble wrote:
> > > > > > > Hi Daniel,
> > > > > > > On Mon, 2014-08-04 at 10:07 +0200, Daniel Vetter wrote:
> > > > > > > > On Fri, Aug 01, 2014 at 12:34:56PM +0530, sagar.a.kamble@intel.com wrote:
> > > > > > > > > From: Sagar Kamble <sagar.a.kamble@intel.com>
> > > > > > > > > @@ -562,7 +567,12 @@ static int i915_drm_freeze(struct drm_device *dev)
> > > > > > > > >  
> > > > > > > > >  	intel_display_set_init_power(dev_priv, false);
> > > > > > > > >  
> > > > > > > > > -	return 0;
> > > > > > > > > +	/* Save Gunit State and clear wake - Need to make sure
> > > > > > > > > +	 * changes in vlv_runtime_suspend path don't impact this path */
> > > > > > > > > +	if (IS_VALLEYVIEW(dev))
> > > > > > > > > +		ret = vlv_runtime_suspend(dev_priv);
> > > > > > > > 
> > > > > > > > Maybe I wasn't clear, but I absolutely don't want any IS_VLV additions to
> > > > > > > > core resume/thaw code. This should be shovelled into the runtime pm
> > > > > > > > handling code, which should be reused in the suspend/resume code.
> > > > > > > This piece of code does not fit into any of the power well get/put path.
> > > > > > > Its specific sequence that need to be followed in VLV when Gunit gets
> > > > > > > power gated. So we have to keep this IS_VLV related functionality in
> > > > > > > both runtime and pm suspend/resume.
> > > > > > 
> > > > > > Well we support S0ix now. Which means our system suspend/resume code
> > > > > > actually calls into the runtime pm code. So either that design is broken
> > > > > > (and we need to fix this) or something else is amiss. Or we don't need
> > > > > > this code any more.
> > > > > > 
> > > > > > But duplicating it is not the right approach. And yeah the power domain
> > > > > > stuff might not be the right place, I've just used that as a place-holder
> > > > > > for all the runtime pm code we have.
> > > > > > -Daniel
> > > > > While entering S0iX we are getting following call flow:
> > > > > intel_runtime_resume followed by i915_drm_freeze 
> > > > > and While resuming back from S0iX:
> > > > > i915_drm_thaw
> > > > > 
> > > > > How can we share that wake control, gunit save/restore functionality?
> > > > > 
> > > > > I am observing issue given below:
> > > > > 
> > > > > 
> > > > > Here is how I am achieving S0ix:
> > > > > 1. echo mem > /sys/power/state
> > > > > 2. (Assuming we have removed all wake_locks in /sys/powe/wake_lock)
> > > > >         If device is runtime suspend it is getting resumed with
> > > > > runtime_resume
> > > > > 3. PM core triggers this sequence for each device
> > > > > (prepare, suspend, suspend_late, suspend_noirq)
> > > > > 4. Then pm_suspend happens for Gfx.
> > > > > 
> > > > > After all devices are suspended S0i0->S0iR->S0i1->S0i2->S0i3 happens.
> > > > > Gunit gets power gated.
> > > > > 
> > > > > While resuming back (with user action/power button press)
> > > > > 1. PM core triggers following sequenc for each device:
> > > > > (resume_noirq, resume_early, resume, complete)
> > > > > 
> > > > > After call to i915_drm_thaw_early(called through resume_early),
> > > > > during i915_drm_thaw(called through resume) we were seeing following
> > > > > issue during ring initialization.
> > > > > This is happening since wake is not enabled and Gunit registers are not
> > > > > restored(which is done in runtime_resume but that path is not taken here
> > > > > since this is resume from pm_suspend)
> > > > 
> > > > We have intel_runtime_pm_get/put calls in the suspend/resume paths which
> > > > should achieve this. Maybe they're not at the right place or not in the
> > > > right ordering, but they're there. So on platforms with runtime pm support
> > > > we _do_ call all the relevant runtime pm callbacks from system
> > > > suspend/resume.
> > > > -Daniel
> > > I am seeing following commit removed get/put calls from suspend resume
> > > paths:
> > > commit 395a5abbd97d7d76a7a26da52f33daebe279b3b3
> > > Author: Jesse Barnes <jbarnes@virtuousgeek.org>
> > > Date:   Wed Jun 18 09:52:56 2014 -0700
> > > 
> > >     drm/i915: don't take runtime PM reference around freeze/thaw
> > >     
> > > 
> > > That ordering of get/put was also incorrect probably. Even though we do
> > > rpm_get before freeze after S0i3 we need to explicitely do wake
> > > contro/gunit save restore.
> > > 
> > > 
> > > In the current patch, the rpm handlers are called directly instead of
> > > (intel_runtime_pm_get/put).
> > > 
> > > valleyview_runtime_suspend at the end of i915_drm_freeze and 
> > > valleyview_runtime_resume at the beginning of i915_drm_thaw_early.
> > > 
> > > Do I need to replace them with intel_display_power_get/put? Will DPM
> > > core allow rpm calls when system pm suspend/resume is in progress?
> > 
> > No, you can't make the device runtime suspend while the system suspend
> > handler runs since DPM takes an RPM reference before calling this
> > handler. The reference will be dropped only after returning from the
> > corresponding system resume handler.
> 
> Blergh, I always forget that little piece of nonsense. Then we just need
> to call the relevant stuff directly, but not the individual platform
> functions but the generic interfaces.

Ok, so I guess I have to unlazy to avoid looking like an incompetent idiot
any longer ;-)

So when Jesse added basic soix support in

commit 8abdc17941c71b37311bb93876ac83dce58160c8
Author: Kristen Carlson Accardi <kristen@linux.intel.com>
Date:   Thu Jun 12 08:35:48 2014 -0700

    drm/i915: make sure PC8 is enabled on suspend and disabled on resume v4

he just added a direct call to the relevant runtime pm function. Which
isn't too cool really, but I merged it.

The next platform that wants this (i.e. you) gets to refactor this so that
we can get rid of the HSW/BDW checks in there and don't need to add
anything else either. So essentially instead of calling platform hooks
directly you shoulc call the relevant driver-internal interfaces/vfuncs.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch