drm/i915: Update DDL only for current CRTC

Instead of looping through all CRTCs, update DDL for current CRTC for which
watermark is being updated.
CHV is confirmed to have precision of 32/64 which is same as VLV.
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Gajanan Bhat <gajanan.bhat@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -1310,24 +1310,17 @@ static bool vlv_compute_drain_latency(struct drm_device *dev,
  * latency value.
  */
 
-static void vlv_update_drain_latency(struct drm_device *dev)
+static void vlv_update_drain_latency(struct drm_crtc *crtc)
 {
+	struct drm_device *dev = crtc->dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
-	enum pipe pipe;
-
-	for_each_pipe(pipe) {
+	enum pipe pipe = to_intel_crtc(crtc)->pipe;
 	int plane_prec, plane_dl;
 	int cursor_prec, cursor_dl;
 	int plane_prec_mult, cursor_prec_mult;
 
-		if (!vlv_compute_drain_latency(dev, pipe, &plane_prec_mult, &plane_dl,
-					       &cursor_prec_mult, &cursor_dl))
-			continue;
-
-		/*
-		 * FIXME CHV spec still lists 16 and 32 as the precision
-		 * values. Need to figure out if spec is outdated or what.
-		 */
+	if (vlv_compute_drain_latency(dev, pipe, &plane_prec_mult, &plane_dl,
+				      &cursor_prec_mult, &cursor_dl)) {
 		cursor_prec = (cursor_prec_mult == DRAIN_LATENCY_PRECISION_64) ?
 			DDL_CURSOR_PRECISION_64 : DDL_CURSOR_PRECISION_32;
 		plane_prec = (plane_prec_mult == DRAIN_LATENCY_PRECISION_64) ?
@@ -1352,7 +1345,7 @@ static void valleyview_update_wm(struct drm_crtc *crtc)
 	unsigned int enabled = 0;
 	bool cxsr_enabled;
 
-	vlv_update_drain_latency(dev);
+	vlv_update_drain_latency(crtc);
 
 	if (g4x_compute_wm0(dev, PIPE_A,
 			    &valleyview_wm_info, latency_ns,