Re: [PATCH 02/11] drm/i915: put runtime PM only at the end of intel_mark_idle

Daniel Vetter
2014-03-05T13:14:53Z

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