drm/i915: Use GPLL ref clock to calculate GPU freqs on VLV/CHV

Extract the GPLL reference frequency from CCK and use it in the
GPU freq<->opcode conversions on VLV/CHV. This eliminates all the
assumptions we have about which divider is used for which czclk
frequency.

Note that unlike most clocks from CCK, the GPLL ref clock is a divided
down version of the CZ clock rather than the HPLL clock. CZ clock itself
is a divided down version of the HPLL clock though, so in effect it just
gets divided down twice.

While at it, throw in a few comments explaining the remaining constants
for anyone who later wants to compare this to the spreadsheets.

v2: Add slow/fast notes for CHV clocks (Imre)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1457120584-26080-2-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com> (v1)

1 files changed, 13 insertions, 6 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index af74cdba7081..cb2d6af7a839 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -147,15 +147,12 @@ static int valleyview_get_vco(struct drm_i915_private *dev_priv)
 	return vco_freq[hpll_freq] * 1000;
 }
 
-static int vlv_get_cck_clock_hpll(struct drm_i915_private *dev_priv,
-				  const char *name, u32 reg)
+int vlv_get_cck_clock(struct drm_i915_private *dev_priv,
+		      const char *name, u32 reg, int ref_freq)
 {
 	u32 val;
 	int divider;
 
-	if (dev_priv->hpll_freq == 0)
-		dev_priv->hpll_freq = valleyview_get_vco(dev_priv);
-
 	mutex_lock(&dev_priv->sb_lock);
 	val = vlv_cck_read(dev_priv, reg);
 	mutex_unlock(&dev_priv->sb_lock);
@@ -166,7 +163,17 @@ static int vlv_get_cck_clock_hpll(struct drm_i915_private *dev_priv,
 	     (divider << CCK_FREQUENCY_STATUS_SHIFT),
 	     "%s change in progress\n", name);
 
-	return DIV_ROUND_CLOSEST(dev_priv->hpll_freq << 1, divider + 1);
+	return DIV_ROUND_CLOSEST(ref_freq << 1, divider + 1);
+}
+
+static int vlv_get_cck_clock_hpll(struct drm_i915_private *dev_priv,
+				  const char *name, u32 reg)
+{
+	if (dev_priv->hpll_freq == 0)
+		dev_priv->hpll_freq = valleyview_get_vco(dev_priv);
+
+	return vlv_get_cck_clock(dev_priv, name, reg,
+				 dev_priv->hpll_freq);
 }
 
 static int