drm/i915: Refactor gen6_set_rps

What used to be a short-circuit now needs to adjust interrupt masking in
response to user requests for changing the min/max allowed frequencies.
This is currently done by a special case and early return, but the next
patch adds another common action to take, so refactor the code to reduce
duplication.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Deepak S <deepak.s@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -3017,36 +3017,30 @@ void gen6_set_rps(struct drm_device *dev, u8 val)
 	WARN_ON(val > dev_priv->rps.max_freq_softlimit);
 	WARN_ON(val < dev_priv->rps.min_freq_softlimit);
 
-	if (val == dev_priv->rps.cur_freq) {
-		/* min/max delay may still have been modified so be sure to
-		 * write the limits value */
-		I915_WRITE(GEN6_RP_INTERRUPT_LIMITS,
-			   gen6_rps_limits(dev_priv, val));
+	/* min/max delay may still have been modified so be sure to
+	 * write the limits value.
+	 */
+	if (val != dev_priv->rps.cur_freq) {
+		gen6_set_rps_thresholds(dev_priv, val);
 
-		return;
+		if (IS_HASWELL(dev))
+			I915_WRITE(GEN6_RPNSWREQ,
+				   HSW_FREQUENCY(val));
+		else
+			I915_WRITE(GEN6_RPNSWREQ,
+				   GEN6_FREQUENCY(val) |
+				   GEN6_OFFSET(0) |
+				   GEN6_AGGRESSIVE_TURBO);
 	}
 
-	gen6_set_rps_thresholds(dev_priv, val);
-
-	if (IS_HASWELL(dev))
-		I915_WRITE(GEN6_RPNSWREQ,
-			   HSW_FREQUENCY(val));
-	else
-		I915_WRITE(GEN6_RPNSWREQ,
-			   GEN6_FREQUENCY(val) |
-			   GEN6_OFFSET(0) |
-			   GEN6_AGGRESSIVE_TURBO);
-
 	/* Make sure we continue to get interrupts
 	 * until we hit the minimum or maximum frequencies.
 	 */
-	I915_WRITE(GEN6_RP_INTERRUPT_LIMITS,
-		   gen6_rps_limits(dev_priv, val));
+	I915_WRITE(GEN6_RP_INTERRUPT_LIMITS, gen6_rps_limits(dev_priv, val));
 
 	POSTING_READ(GEN6_RPNSWREQ);
 
 	dev_priv->rps.cur_freq = val;
-
 	trace_intel_gpu_freq_change(val * 50);
 }