[Intel-gfx] [PATCH] drm/i915: make sure GPU freq drops to minimum after entering RC6 v3

[Ville Syrjälä]

On Tue, Apr 23, 2013 at 11:45:03AM +0300, Jani Nikula wrote:
> On Tue, 23 Apr 2013, Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
> > On VLV, the Punit doesn't automatically drop the GPU to it's minimum
> > voltage level when entering RC6, so we arm a timer to do it for us from
> > the RPS interrupt handler.  It'll generally only fire when we go idle
> > (or if for some reason there's a long delay between RPS interrupts), but
> > won't be re-armed again until the next RPS event, so shouldn't affect
> > power consumption after we go idle and it triggers.
> >
> > v2: use delayed work instead of timer + work queue combo (Ville)
> > v3: fix up delayed work cancel (must be outside lock) (Daniel)
> >     fix up delayed work handling func for delayed work (Jesse)
> >
> > Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
> > ---
> >  drivers/gpu/drm/i915/i915_drv.h |    2 ++
> >  drivers/gpu/drm/i915/i915_irq.c |   11 +++++++++++
> >  drivers/gpu/drm/i915/intel_pm.c |   22 ++++++++++++++++++++++
> >  3 files changed, 35 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > index 2557fc7..f563f25 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -660,6 +660,7 @@ struct i915_suspend_saved_registers {
> >  
> >  struct intel_gen6_power_mgmt {
> >  	struct work_struct work;
> > +	struct delayed_work vlv_work;
> >  	u32 pm_iir;
> >  	/* lock - irqsave spinlock that protectects the work_struct and
> >  	 * pm_iir. */
> > @@ -670,6 +671,7 @@ struct intel_gen6_power_mgmt {
> >  	u8 cur_delay;
> >  	u8 min_delay;
> >  	u8 max_delay;
> > +	u8 rpe_delay;
> >  	u8 hw_max;
> >  
> >  	struct delayed_work delayed_resume_work;
> > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> > index 932e7f8..af385e2 100644
> > --- a/drivers/gpu/drm/i915/i915_irq.c
> > +++ b/drivers/gpu/drm/i915/i915_irq.c
> > @@ -488,6 +488,17 @@ static void gen6_pm_rps_work(struct work_struct *work)
> >  			gen6_set_rps(dev_priv->dev, new_delay);
> >  	}
> >  
> > +	if (IS_VALLEYVIEW(dev_priv->dev)) {
> > +		/*
> > +		 * On VLV, when we enter RC6 we may not be at the minimum
> > +		 * voltage level, so arm a timer to check.  It should only
> > +		 * fire when there's activity or once after we've entered
> > +		 * RC6, and then won't be re-armed until the next RPS interrupt.
> > +		 */
> > +		mod_delayed_work(dev_priv->wq, &dev_priv->rps.vlv_work,
> > +				 jiffies + msecs_to_jiffies(100));
> 
> Hooray for conflicting semantics. Unlike mod_timer, mod_delayed_work
> wants a delay, not an absolute time in jiffies.
> 
> > +	}
> > +
> >  	mutex_unlock(&dev_priv->rps.hw_lock);
> >  }
> >  
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> > index 2557926..c106187 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -2822,6 +2822,23 @@ int valleyview_rps_min_freq(struct drm_i915_private *dev_priv)
> >  	return val & 0xff;
> >  }
> >  
> > +static void vlv_rps_timer_work(struct work_struct *work)
> > +{
> > +	drm_i915_private_t *dev_priv = container_of(work, drm_i915_private_t,
> > +						    rps.vlv_work.work);
> > +
> > +	/*
> > +	 * Timer fired, we must be idle.  Drop to min voltage state.
> > +	 * Note: we use RPe here since it should match the
> > +	 * Vmin we were shooting for.  That should give us better
> > +	 * perf when we come back out of RC6 than if we used the
> > +	 * min freq available.
> > +	 */
> > +	mutex_lock(&dev_priv->rps.hw_lock);
> > +	valleyview_set_rps(dev_priv->dev, dev_priv->rps.rpe_delay);
> > +	mutex_unlock(&dev_priv->rps.hw_lock);
> > +}
> > +
> >  static void valleyview_enable_rps(struct drm_device *dev)
> >  {
> >  	struct drm_i915_private *dev_priv = dev->dev_private;
> > @@ -2886,6 +2903,7 @@ static void valleyview_enable_rps(struct drm_device *dev)
> >  	rpe = valleyview_rps_rpe_freq(dev_priv);
> >  	DRM_DEBUG_DRIVER("RPe GPU freq: %d\n",
> >  			 vlv_gpu_freq(dev_priv->mem_freq, rpe));
> > +	dev_priv->rps.rpe_delay = rpe;
> >  
> >  	val = valleyview_rps_min_freq(dev_priv);
> >  	DRM_DEBUG_DRIVER("min GPU freq: %d\n", vlv_gpu_freq(dev_priv->mem_freq,
> > @@ -2895,6 +2913,8 @@ static void valleyview_enable_rps(struct drm_device *dev)
> >  	DRM_DEBUG_DRIVER("setting GPU freq to %d\n",
> >  			 vlv_gpu_freq(dev_priv->mem_freq, rpe));
> >  
> > +	INIT_DELAYED_WORK(&dev_priv->rps.vlv_work, vlv_rps_timer_work);
> > +
> >  	valleyview_set_rps(dev_priv->dev, rpe);
> >  
> >  	/* requires MSI enabled */
> > @@ -3640,6 +3660,8 @@ void intel_disable_gt_powersave(struct drm_device *dev)
> >  		mutex_lock(&dev_priv->rps.hw_lock);
> >  		gen6_disable_rps(dev);
> >  		mutex_unlock(&dev_priv->rps.hw_lock);
> 
> Theoretically the work could get executed here, between unlock and
> cancel. Does that matter?

AFAICS even gen6_pm_rps_work() might be executing even after
gen6_disable_rps() was called.

I'm not quite sure if allowing gen6_pm_rps_work() to do stuff after
gen6_disable_rps() was called is already a problem on it's own. At
least it can overwrite RPNSWREQ on !VLV. BTW that register doesn't seem
to exist on VLV and yet we're poking at it from gen6_disable_rps()...

> 
> > +		if (IS_VALLEYVIEW(dev))
> > +			cancel_delayed_work_sync(&dev_priv->rps.vlv_work);
> >  	}
> >  }
> >  
> > -- 
> > 1.7.10.4
> >
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-- 
Ville Syrjälä
Intel OTC