drm/i915: make sure GPU freq drops to minimum after entering RC6 v4

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)
v4: cancel delayed work before RPS shutdown (Jani)
    pass delay not absolute time to mod_delayed_work (Jani)
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -653,6 +653,7 @@ 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. */
@@ -663,6 +664,7 @@ 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;

drivers/gpu/drm/i915/i915_irq.c

@@ -725,6 +725,17 @@ 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,
+				 msecs_to_jiffies(100));
+	}
+
 	mutex_unlock(&dev_priv->rps.hw_lock);
 }
 

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 */
@@ -3637,6 +3657,8 @@ void intel_disable_gt_powersave(struct drm_device *dev)
 		ironlake_disable_rc6(dev);
 	} else if (INTEL_INFO(dev)->gen >= 6) {
 		cancel_delayed_work_sync(&dev_priv->rps.delayed_resume_work);
+		if (IS_VALLEYVIEW(dev))
+			cancel_delayed_work_sync(&dev_priv->rps.vlv_work);
 		mutex_lock(&dev_priv->rps.hw_lock);
 		gen6_disable_rps(dev);
 		mutex_unlock(&dev_priv->rps.hw_lock);