From mboxrd@z Thu Jan  1 00:00:00 1970
From: Daniel Vetter <daniel@ffwll.ch>
Subject: Re: [PATCH 02/11] drm/i915: put runtime PM only at the
 end of intel_mark_idle
Date: Wed, 5 Mar 2014 14:14:47 +0100
Message-ID: <20140305131447.GH17001@phenom.ffwll.local>
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To: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: intel-gfx@lists.freedesktop.org, Paulo Zanoni <paulo.r.zanoni@intel.com>
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On Fri, Feb 21, 2014 at 09:28:25AM -0800, Jesse Barnes wrote:
> On Fri, 21 Feb 2014 13:52:19 -0300
> Paulo Zanoni <przanoni@gmail.com> wrote:
> 
> > From: Paulo Zanoni <paulo.r.zanoni@intel.com>
> > 
> > Because intel_mark_idle still touches some registers: it needs the
> > machine to be awake. If you set both the autosuspend and PC8 delays to
> > zero, you can get a "Device suspended" WARN when gen6_rps_idle touches
> > registers.
> > 
> > This is not easy to reproduce, but happens once in a while when
> > running pm_pc8.
> > 
> > Testcase: igt/pm_pc8
> > Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_display.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index dd416f2..10ec401 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -8210,10 +8210,8 @@ void intel_mark_idle(struct drm_device *dev)
> >  
> >  	dev_priv->mm.busy = false;
> >  
> > -	hsw_package_c8_gpu_idle(dev_priv);
> > -
> >  	if (!i915.powersave)
> > -		return;
> > +		goto out;
> >  
> >  	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
> >  		if (!crtc->fb)
> > @@ -8224,6 +8222,9 @@ void intel_mark_idle(struct drm_device *dev)
> >  
> >  	if (INTEL_INFO(dev)->gen >= 6)
> >  		gen6_rps_idle(dev->dev_private);
> > +
> > +out:
> > +	hsw_package_c8_gpu_idle(dev_priv);
> >  }
> >  
> >  void intel_mark_fb_busy(struct drm_i915_gem_object *obj,
> 
> Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>

Smells like another good reason for Jesse's idea with a register range
based power domain checker. Especially with suspend delays we'll have a
really hard time catching these kinds of bugs otherwise ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch