drm/i915: factor out intel_set_cpu_fifo_underrun_reporting_nolock

Needed by the next patch, wanting to set the underrun reporting as part
of a bigger dev_priv->irq_lock'ed sequence.
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
[danvet: Use more customary __ prefix instead of _nolock postfix.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_irq.c

@@ -387,17 +387,14 @@ static void cpt_set_fifo_underrun_reporting(struct drm_device *dev,
  *
  * Returns the previous state of underrun reporting.
  */
-bool intel_set_cpu_fifo_underrun_reporting(struct drm_device *dev,
+bool __intel_set_cpu_fifo_underrun_reporting(struct drm_device *dev,
 					     enum pipe pipe, bool enable)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct drm_crtc *crtc = dev_priv->pipe_to_crtc_mapping[pipe];
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
-	unsigned long flags;
 	bool ret;
 
-	spin_lock_irqsave(&dev_priv->irq_lock, flags);
-
 	ret = !intel_crtc->cpu_fifo_underrun_disabled;
 
 	if (enable == ret)
@@ -415,7 +412,20 @@ bool intel_set_cpu_fifo_underrun_reporting(struct drm_device *dev,
 		broadwell_set_fifo_underrun_reporting(dev, pipe, enable);
 
 done:
+	return ret;
+}
+
+bool intel_set_cpu_fifo_underrun_reporting(struct drm_device *dev,
+					   enum pipe pipe, bool enable)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	unsigned long flags;
+	bool ret;
+
+	spin_lock_irqsave(&dev_priv->irq_lock, flags);
+	ret = __intel_set_cpu_fifo_underrun_reporting(dev, pipe, enable);
 	spin_unlock_irqrestore(&dev_priv->irq_lock, flags);
+
 	return ret;
 }