drm/i915: Avoid tweaking RPS before it is enabled

As we delay the initial RPS enabling (upon boot and after resume), there
is a chance that we may start to render and trigger RPS boosts before we
set up the punit. Any changes we make could result in inconsistent
hardware state, with a danger of causing undefined behaviour. However,
as the boosting is a optional tweak to RPS, we can simply ignore it
whilst RPS is not yet enabled.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -862,6 +862,7 @@ struct intel_gen6_power_mgmt {
 	int last_adj;
 	enum { LOW_POWER, BETWEEN, HIGH_POWER } power;
 
+	bool enabled;
 	struct delayed_work delayed_resume_work;
 
 	/*

drivers/gpu/drm/i915/intel_pm.c

@@ -3442,22 +3442,26 @@ void gen6_set_rps(struct drm_device *dev, u8 val)
 void gen6_rps_idle(struct drm_i915_private *dev_priv)
 {
 	mutex_lock(&dev_priv->rps.hw_lock);
+	if (dev_priv->rps.enabled) {
 		if (dev_priv->info->is_valleyview)
 			valleyview_set_rps(dev_priv->dev, dev_priv->rps.min_delay);
 		else
 			gen6_set_rps(dev_priv->dev, dev_priv->rps.min_delay);
 		dev_priv->rps.last_adj = 0;
+	}
 	mutex_unlock(&dev_priv->rps.hw_lock);
 }
 
 void gen6_rps_boost(struct drm_i915_private *dev_priv)
 {
 	mutex_lock(&dev_priv->rps.hw_lock);
+	if (dev_priv->rps.enabled) {
 		if (dev_priv->info->is_valleyview)
 			valleyview_set_rps(dev_priv->dev, dev_priv->rps.max_delay);
 		else
 			gen6_set_rps(dev_priv->dev, dev_priv->rps.max_delay);
 		dev_priv->rps.last_adj = 0;
+	}
 	mutex_unlock(&dev_priv->rps.hw_lock);
 }
 
@@ -4716,6 +4720,7 @@ void intel_disable_gt_powersave(struct drm_device *dev)
 			valleyview_disable_rps(dev);
 		else
 			gen6_disable_rps(dev);
+		dev_priv->rps.enabled = false;
 		mutex_unlock(&dev_priv->rps.hw_lock);
 	}
 }
@@ -4735,6 +4740,7 @@ static void intel_gen6_powersave_work(struct work_struct *work)
 		gen6_enable_rps(dev);
 		gen6_update_ring_freq(dev);
 	}
+	dev_priv->rps.enabled = true;
 	mutex_unlock(&dev_priv->rps.hw_lock);
 }