drm/i915: Extract skl_calc_cdclk()

We have many places where we want to pick a suitable cdclk frequency for
skl based on the dotclock and lcpll vco. Split that code into a small
helper and call it from all over.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1463172100-24715-5-git-send-email-ville.syrjala@linux.intel.comReviewed-by: Imre Deak <imre.deak@intel.com>

drivers/gpu/drm/i915/intel_display.c

@@ -5447,6 +5447,30 @@ void broxton_uninit_cdclk(struct drm_i915_private *dev_priv)
 	broxton_set_cdclk(dev_priv, 19200);
 }
 
+static int skl_calc_cdclk(int max_pixclk, int vco)
+{
+	if (vco == 8640) {
+		if (max_pixclk > 540000)
+			return 617140;
+		else if (max_pixclk > 432000)
+			return 540000;
+		else if (max_pixclk > 308570)
+			return 432000;
+		else
+			return 308570;
+	} else {
+		/* VCO 8100 */
+		if (max_pixclk > 540000)
+			return 675000;
+		else if (max_pixclk > 450000)
+			return 540000;
+		else if (max_pixclk > 337500)
+			return 450000;
+		else
+			return 337500;
+	}
+}
+
 static const struct skl_cdclk_entry {
 	unsigned int freq;
 	unsigned int vco;
@@ -5477,15 +5501,10 @@ unsigned int skl_cdclk_get_vco(unsigned int freq)
 static void
 skl_dpll0_enable(struct drm_i915_private *dev_priv, int vco)
 {
-	int min_cdclk;
+	int min_cdclk = skl_calc_cdclk(0, vco);
 	u32 val;
 
 	/* select the minimum CDCLK before enabling DPLL 0 */
-	if (vco == 8640)
-		min_cdclk = 308570;
-	else
-		min_cdclk = 337500;
-
 	val = CDCLK_FREQ_337_308 | skl_cdclk_decimal(min_cdclk);
 	I915_WRITE(CDCLK_CTL, val);
 	POSTING_READ(CDCLK_CTL);
@@ -5497,7 +5516,7 @@ skl_dpll0_enable(struct drm_i915_private *dev_priv, int vco)
 	 * 8100 while the eDP 1.4 alternate link rates need a VCO of 8640.
 	 * The modeset code is responsible for the selection of the exact link
 	 * rate later on, with the constraint of choosing a frequency that
-	 * works with required_vco.
+	 * works with vco.
 	 */
 	val = I915_READ(DPLL_CTRL1);
 
@@ -5626,7 +5645,7 @@ void skl_init_cdclk(struct drm_i915_private *dev_priv)
 		if (dev_priv->skl_vco_freq != 8640)
 			dev_priv->skl_vco_freq = 8100;
 		skl_dpll0_enable(dev_priv, dev_priv->skl_vco_freq);
-		cdclk = ((dev_priv->skl_vco_freq == 8100) ? 337500 : 308570);
+		cdclk = skl_calc_cdclk(0, dev_priv->skl_vco_freq);
 	} else {
 		cdclk = dev_priv->cdclk_freq;
 	}
@@ -9650,34 +9669,14 @@ static int skl_modeset_calc_cdclk(struct drm_atomic_state *state)
 	struct intel_atomic_state *intel_state = to_intel_atomic_state(state);
 	struct drm_i915_private *dev_priv = to_i915(state->dev);
 	const int max_pixclk = ilk_max_pixel_rate(state);
+	int vco = intel_state->cdclk_pll_vco;
 	int cdclk;
 
 	/*
 	 * FIXME should also account for plane ratio
 	 * once 64bpp pixel formats are supported.
 	 */
-
-	if (intel_state->cdclk_pll_vco == 8640) {
-		/* vco 8640 */
-		if (max_pixclk > 540000)
-			cdclk = 617140;
-		else if (max_pixclk > 432000)
-			cdclk = 540000;
-		else if (max_pixclk > 308570)
-			cdclk = 432000;
-		else
-			cdclk = 308570;
-	} else {
-		/* VCO 8100 */
-		if (max_pixclk > 540000)
-			cdclk = 675000;
-		else if (max_pixclk > 450000)
-			cdclk = 540000;
-		else if (max_pixclk > 337500)
-			cdclk = 450000;
-		else
-			cdclk = 337500;
-	}
+	cdclk = skl_calc_cdclk(max_pixclk, vco);
 
 	/*
 	 * FIXME move the cdclk caclulation to
@@ -9691,9 +9690,7 @@ static int skl_modeset_calc_cdclk(struct drm_atomic_state *state)
 
 	intel_state->cdclk = intel_state->dev_cdclk = cdclk;
 	if (!intel_state->active_crtcs)
-		intel_state->dev_cdclk = ((intel_state->cdclk_pll_vco == 8640) ?
-					   308570 : 337500);
-
+		intel_state->dev_cdclk = skl_calc_cdclk(0, vco);
 
 	return 0;
 }