drm/i915: Read out hrawclk from CCK on vlv/chv

Currently we assume that hrawclk is 200MHz on VLV/CHV. That should
be true always, but just to avoid such asumptions we can read out the
actual frequency from CCK.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1456932138-14004-5-git-send-email-ville.syrjala@linux.intel.comReviewed-by: Imre Deak <imre.deak@intel.com>

drivers/gpu/drm/i915/i915_reg.h

@@ -786,6 +786,7 @@ enum skl_disp_power_wells {
 #define  DSI_PLL_M1_DIV_MASK			(0x1ff << 0)
 #define CCK_CZ_CLOCK_CONTROL			0x62
 #define CCK_DISPLAY_CLOCK_CONTROL		0x6b
+#define CCK_DISPLAY_REF_CLOCK_CONTROL		0x6c
 #define  CCK_TRUNK_FORCE_ON			(1 << 17)
 #define  CCK_TRUNK_FORCE_OFF			(1 << 16)
 #define  CCK_FREQUENCY_STATUS			(0x1f << 8)

drivers/gpu/drm/i915/intel_display.c

@@ -178,7 +178,8 @@ intel_pch_rawclk(struct drm_i915_private *dev_priv)
 static int
 intel_vlv_hrawclk(struct drm_i915_private *dev_priv)
 {
-	return 200000;
+	return vlv_get_cck_clock_hpll(dev_priv, "hrawclk",
+				      CCK_DISPLAY_REF_CLOCK_CONTROL);
 }
 
 static int