drm/i915: FIFO space query code refactor

When querying the GTFIFOCTL register to check the FIFO space, the read value
must be masked. The operation is repeated explicitly in several places. This
change refactors the read-and-mask code into a function call.

v2: rebased on top of Mika's forcewake patch set, specifically:
	[PATCH 8/8] drm/i915: Enum forcewake domains and domain identifiers

Change-Id: Id1a9f3785cb20b82d4caa330c37b31e4e384a3ef
Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_uncore.c

@@ -210,23 +210,29 @@ static void fw_domains_put_with_fifo(struct drm_i915_private *dev_priv,
 	gen6_gt_check_fifodbg(dev_priv);
 }
 
+static inline u32 fifo_free_entries(struct drm_i915_private *dev_priv)
+{
+	u32 count = __raw_i915_read32(dev_priv, GTFIFOCTL);
+
+	return count & GT_FIFO_FREE_ENTRIES_MASK;
+}
+
 static int __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv)
 {
 	int ret = 0;
 
 	/* On VLV, FIFO will be shared by both SW and HW.
 	 * So, we need to read the FREE_ENTRIES everytime */
 	if (IS_VALLEYVIEW(dev_priv->dev))
-		dev_priv->uncore.fifo_count =
-			__raw_i915_read32(dev_priv, GTFIFOCTL) &
-						GT_FIFO_FREE_ENTRIES_MASK;
+		dev_priv->uncore.fifo_count = fifo_free_entries(dev_priv);
 
 	if (dev_priv->uncore.fifo_count < GT_FIFO_NUM_RESERVED_ENTRIES) {
 		int loop = 500;
-		u32 fifo = __raw_i915_read32(dev_priv, GTFIFOCTL) & GT_FIFO_FREE_ENTRIES_MASK;
+		u32 fifo = fifo_free_entries(dev_priv);
+
 		while (fifo <= GT_FIFO_NUM_RESERVED_ENTRIES && loop--) {
 			udelay(10);
-			fifo = __raw_i915_read32(dev_priv, GTFIFOCTL) & GT_FIFO_FREE_ENTRIES_MASK;
+			fifo = fifo_free_entries(dev_priv);
 		}
 		if (WARN_ON(loop < 0 && fifo <= GT_FIFO_NUM_RESERVED_ENTRIES))
 			++ret;
@@ -314,8 +320,7 @@ void intel_uncore_forcewake_reset(struct drm_device *dev, bool restore)
 
 		if (IS_GEN6(dev) || IS_GEN7(dev))
 			dev_priv->uncore.fifo_count =
-				__raw_i915_read32(dev_priv, GTFIFOCTL) &
-				GT_FIFO_FREE_ENTRIES_MASK;
+				fifo_free_entries(dev_priv);
 	}
 
 	if (!restore)