drm/i915: Accurately initialize fifo underrun state on gmch platforms

We don't have hardware based disable bits on gmch platforms, so need
to block spurious underrun reports in software. Which means that we
_must_ start out with fifo underrun reporting disabled everywhere.

This is in big contrast to ilk/hsw/cpt where there's only _one_
disable bit for all platforms and hence we must allow underrun
reporting on disabled pipes. Otherwise nothing really works,
especially the CRC support since that's key'ed off the same irq
disable bit.

This allows us to ditch the fifo underrun reporting hack from the vlv
runtime pm code and unexport the internal function from i915_irq.c
again. Yay!

v2: Keep the display irq disabling, spotted by Imre.

Cc: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_irq.c

@@ -415,8 +415,8 @@ 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,
-					     enum pipe pipe, bool enable)
+static 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];

drivers/gpu/drm/i915/intel_display.c

@@ -11504,11 +11504,18 @@ static void intel_sanitize_crtc(struct intel_crtc *crtc)
 			encoder->base.crtc = NULL;
 		}
 	}
-	if (crtc->active) {
+
+	if (crtc->active || IS_VALLEYVIEW(dev) || INTEL_INFO(dev)->gen < 5) {
 		/*
 		 * We start out with underrun reporting disabled to avoid races.
 		 * For correct bookkeeping mark this on active crtcs.
 		 *
+		 * Also on gmch platforms we dont have any hardware bits to
+		 * disable the underrun reporting. Which means we need to start
+		 * out with underrun reporting disabled also on inactive pipes,
+		 * since otherwise we'll complain about the garbage we read when
+		 * e.g. coming up after runtime pm.
+		 *
 		 * No protection against concurrent access is required - at
 		 * worst a fifo underrun happens which also sets this to false.
 		 */

drivers/gpu/drm/i915/intel_drv.h

@@ -644,8 +644,6 @@ hdmi_to_dig_port(struct intel_hdmi *intel_hdmi)
 /* i915_irq.c */
 bool intel_set_cpu_fifo_underrun_reporting(struct drm_device *dev,
 					   enum pipe pipe, bool enable);
-bool __intel_set_cpu_fifo_underrun_reporting(struct drm_device *dev,
-					     enum pipe pipe, bool enable);
 bool intel_set_pch_fifo_underrun_reporting(struct drm_device *dev,
 					   enum transcoder pch_transcoder,
 					   bool enable);

drivers/gpu/drm/i915/intel_pm.c

@@ -5729,15 +5729,9 @@ static void vlv_display_power_well_enable(struct drm_i915_private *dev_priv,
 static void vlv_display_power_well_disable(struct drm_i915_private *dev_priv,
 					   struct i915_power_well *power_well)
 {
-	struct drm_device *dev = dev_priv->dev;
-	enum pipe pipe;
-
 	WARN_ON_ONCE(power_well->data != PUNIT_POWER_WELL_DISP2D);
 
 	spin_lock_irq(&dev_priv->irq_lock);
-	for_each_pipe(pipe)
-		__intel_set_cpu_fifo_underrun_reporting(dev, pipe, false);
-
 	valleyview_disable_display_irqs(dev_priv);
 	spin_unlock_irq(&dev_priv->irq_lock);