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_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 5fd6a5d..a569597 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -847,6 +847,8 @@
 	drm_i915_private_t *dev_priv = dev->dev_private;
 	int ret;
 
+	flush_delayed_work(&dev_priv->rps.delayed_resume_work);
+
 	if (IS_GEN5(dev)) {
 		u16 rgvswctl = I915_READ16(MEMSWCTL);
 		u16 rgvstat = I915_READ16(MEMSTAT_ILK);
@@ -1325,6 +1327,8 @@
 		return 0;
 	}
 
+	flush_delayed_work(&dev_priv->rps.delayed_resume_work);
+
 	ret = mutex_lock_interruptible(&dev_priv->rps.hw_lock);
 	if (ret)
 		return ret;
@@ -1940,6 +1944,8 @@
 	if (!(IS_GEN6(dev) || IS_GEN7(dev)))
 		return -ENODEV;
 
+	flush_delayed_work(&dev_priv->rps.delayed_resume_work);
+
 	ret = mutex_lock_interruptible(&dev_priv->rps.hw_lock);
 	if (ret)
 		return ret;
@@ -1964,6 +1970,8 @@
 	if (!(IS_GEN6(dev) || IS_GEN7(dev)))
 		return -ENODEV;
 
+	flush_delayed_work(&dev_priv->rps.delayed_resume_work);
+
 	DRM_DEBUG_DRIVER("Manually setting max freq to %llu\n", val);
 
 	ret = mutex_lock_interruptible(&dev_priv->rps.hw_lock);
@@ -2002,6 +2010,8 @@
 	if (!(IS_GEN6(dev) || IS_GEN7(dev)))
 		return -ENODEV;
 
+	flush_delayed_work(&dev_priv->rps.delayed_resume_work);
+
 	ret = mutex_lock_interruptible(&dev_priv->rps.hw_lock);
 	if (ret)
 		return ret;
@@ -2026,6 +2036,8 @@
 	if (!(IS_GEN6(dev) || IS_GEN7(dev)))
 		return -ENODEV;
 
+	flush_delayed_work(&dev_priv->rps.delayed_resume_work);
+
 	DRM_DEBUG_DRIVER("Manually setting min freq to %llu\n", val);
 
 	ret = mutex_lock_interruptible(&dev_priv->rps.hw_lock);