drm/i915: Finish enabling rps before use by sysfs or debugfs

Enabling rps (turbo setup) was put in a work queue because it may
take quite awhile.  This change flushes the work queue to initialize
rps values before use by sysfs or debugfs.  Specifically,
rps.delayed_resume_work is flushed before using rps.hw_max,
rps.max_delay, rps.min_delay, or rps.cur_delay.

This change fixes a problem in sysfs where show functions using
uninitialized values show incorrect values and store functions
using uninitialized values in range checks incorrectly fail to
store valid input values.  This change also addresses similar use
before initialized problems in debugfs.

Signed-off-by: Tom O'Rourke <Tom.O'Rourke@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_sysfs.c b/drivers/gpu/drm/i915/i915_sysfs.c
index 8003886..9ff1e4d 100644
--- a/drivers/gpu/drm/i915/i915_sysfs.c
+++ b/drivers/gpu/drm/i915/i915_sysfs.c
@@ -251,6 +251,8 @@
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int ret;
 
+	flush_delayed_work(&dev_priv->rps.delayed_resume_work);
+
 	mutex_lock(&dev_priv->rps.hw_lock);
 	if (IS_VALLEYVIEW(dev_priv->dev)) {
 		u32 freq;
@@ -283,6 +285,8 @@
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int ret;
 
+	flush_delayed_work(&dev_priv->rps.delayed_resume_work);
+
 	mutex_lock(&dev_priv->rps.hw_lock);
 	if (IS_VALLEYVIEW(dev_priv->dev))
 		ret = vlv_gpu_freq(dev_priv->mem_freq, dev_priv->rps.max_delay);
@@ -307,6 +311,8 @@
 	if (ret)
 		return ret;
 
+	flush_delayed_work(&dev_priv->rps.delayed_resume_work);
+
 	mutex_lock(&dev_priv->rps.hw_lock);
 
 	if (IS_VALLEYVIEW(dev_priv->dev)) {
@@ -355,6 +361,8 @@
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int ret;
 
+	flush_delayed_work(&dev_priv->rps.delayed_resume_work);
+
 	mutex_lock(&dev_priv->rps.hw_lock);
 	if (IS_VALLEYVIEW(dev_priv->dev))
 		ret = vlv_gpu_freq(dev_priv->mem_freq, dev_priv->rps.min_delay);
@@ -379,6 +387,8 @@
 	if (ret)
 		return ret;
 
+	flush_delayed_work(&dev_priv->rps.delayed_resume_work);
+
 	mutex_lock(&dev_priv->rps.hw_lock);
 
 	if (IS_VALLEYVIEW(dev)) {