drm/i915: Allow pixel clock up to 95% of cdclk on CHV

Supposedly CHV can sustain a pixel clock of up to 95% of
cdclk, as opposed to the 90% limit that was used old older
platforms. Update the cdclk selection code to allow for this.

This will allow eg. HDMI 4k modes with their 297MHz pixel clock
while still respecting the 320 MHz cdclk limit on CHV.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Vijay Purushothaman <vijay.a.purushothaman@linux.intel.com>
Reviewed-by: Yogesh Mohan Marimuthu <yogesh.mohan.marimuthu@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -5038,6 +5038,7 @@ static int valleyview_calc_cdclk(struct drm_i915_private *dev_priv,
 				 int max_pixclk)
 {
 	int freq_320 = (dev_priv->hpll_freq <<  1) % 320000 != 0 ? 333333 : 320000;
+	int limit = IS_CHERRYVIEW(dev_priv) ? 95 : 90;
 
 	/* FIXME: Punit isn't quite ready yet */
 	if (IS_CHERRYVIEW(dev_priv->dev))
@@ -5048,17 +5049,18 @@ static int valleyview_calc_cdclk(struct drm_i915_private *dev_priv,
 	 *   200MHz
 	 *   267MHz
 	 *   320/333MHz (depends on HPLL freq)
-	 *   400MHz
-	 * So we check to see whether we're above 90% of the lower bin and
-	 * adjust if needed.
+	 *   400MHz (VLV only)
+	 * So we check to see whether we're above 90% (VLV) or 95% (CHV)
+	 * of the lower bin and adjust if needed.
 	 *
 	 * We seem to get an unstable or solid color picture at 200MHz.
 	 * Not sure what's wrong. For now use 200MHz only when all pipes
 	 * are off.
 	 */
-	if (max_pixclk > freq_320*9/10)
+	if (!IS_CHERRYVIEW(dev_priv) &&
+	    max_pixclk > freq_320*limit/100)
 		return 400000;
-	else if (max_pixclk > 266667*9/10)
+	else if (max_pixclk > 266667*limit/100)
 		return freq_320;
 	else if (max_pixclk > 0)
 		return 266667;