drm/i915: vlv: cache current CD clock rate

Instead of reading out the CD clock rate from the HW at each modeset, do
this only during driver init and resume and use the cached value during
modeset. This moves things towards a state where the sw and hw side
setup is separated. It's also needed for VLV RPM, where we don't put
device into D0 state until modeset_global_resources is called and thus
can't access any display/gfx registers.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Antti Koskipää <antti.koskipaa@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index c31c620..451eef7 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4201,6 +4201,9 @@
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	u32 val, cmd;
 
+	WARN_ON(valleyview_cur_cdclk(dev_priv) != dev_priv->vlv_cdclk_freq);
+	dev_priv->vlv_cdclk_freq = cdclk;
+
 	if (cdclk >= 320) /* jump to highest voltage for 400MHz too */
 		cmd = 2;
 	else if (cdclk == 266)
@@ -4255,7 +4258,7 @@
 	intel_i2c_reset(dev);
 }
 
-static int valleyview_cur_cdclk(struct drm_i915_private *dev_priv)
+int valleyview_cur_cdclk(struct drm_i915_private *dev_priv)
 {
 	int cur_cdclk, vco;
 	int divider;
@@ -4276,10 +4279,6 @@
 static int valleyview_calc_cdclk(struct drm_i915_private *dev_priv,
 				 int max_pixclk)
 {
-	int cur_cdclk;
-
-	cur_cdclk = valleyview_cur_cdclk(dev_priv);
-
 	/*
 	 * Really only a few cases to deal with, as only 4 CDclks are supported:
 	 *   200MHz
@@ -4321,9 +4320,9 @@
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_crtc *intel_crtc;
 	int max_pixclk = intel_mode_max_pixclk(dev_priv);
-	int cur_cdclk = valleyview_cur_cdclk(dev_priv);
 
-	if (valleyview_calc_cdclk(dev_priv, max_pixclk) == cur_cdclk)
+	if (valleyview_calc_cdclk(dev_priv, max_pixclk) ==
+	    dev_priv->vlv_cdclk_freq)
 		return;
 
 	/* disable/enable all currently active pipes while we change cdclk */
@@ -4337,10 +4336,9 @@
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int max_pixclk = intel_mode_max_pixclk(dev_priv);
-	int cur_cdclk = valleyview_cur_cdclk(dev_priv);
 	int req_cdclk = valleyview_calc_cdclk(dev_priv, max_pixclk);
 
-	if (req_cdclk != cur_cdclk)
+	if (req_cdclk != dev_priv->vlv_cdclk_freq)
 		valleyview_set_cdclk(dev, req_cdclk);
 	modeset_update_crtc_power_domains(dev);
 }