drm/i915: Allow enable/disable of DPLL0 around cdclk changes on SKL

In case we originally guessed wrong which lcpll vco frequency to use,
we will need to shut down the pll and restart it when reprogamming the
cdclk.

This also allows us to track the actual vco frequency in dev_priv
instead of just a guess.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1463172100-24715-8-git-send-email-ville.syrjala@linux.intel.comReviewed-by: Imre Deak <imre.deak@intel.com>

drivers/gpu/drm/i915/intel_display.c

@@ -5546,6 +5546,8 @@ skl_dpll0_enable(struct drm_i915_private *dev_priv, int vco)
 
 	if (wait_for(I915_READ(LCPLL1_CTL) & LCPLL_PLL_LOCK, 5))
 		DRM_ERROR("DPLL0 not locked\n");
+
+	dev_priv->skl_vco_freq = vco;
 }
 
 static void
@@ -5554,6 +5556,8 @@ skl_dpll0_disable(struct drm_i915_private *dev_priv)
 	I915_WRITE(LCPLL1_CTL, I915_READ(LCPLL1_CTL) & ~LCPLL_PLL_ENABLE);
 	if (wait_for(!(I915_READ(LCPLL1_CTL) & LCPLL_PLL_LOCK), 1))
 		DRM_ERROR("Couldn't disable DPLL0\n");
+
+	dev_priv->skl_vco_freq = 0;
 }
 
 static bool skl_cdclk_pcu_ready(struct drm_i915_private *dev_priv)
@@ -5583,12 +5587,14 @@ static bool skl_cdclk_wait_for_pcu_ready(struct drm_i915_private *dev_priv)
 	return false;
 }
 
-static void skl_set_cdclk(struct drm_i915_private *dev_priv, int cdclk)
+static void skl_set_cdclk(struct drm_i915_private *dev_priv, int cdclk, int vco)
 {
 	struct drm_device *dev = dev_priv->dev;
 	u32 freq_select, pcu_ack;
 
-	DRM_DEBUG_DRIVER("Changing CDCLK to %dKHz\n", cdclk);
+	WARN_ON((cdclk == 24000) != (vco == 0));
+
+	DRM_DEBUG_DRIVER("Changing CDCLK to %d kHz (VCO %d MHz)\n", cdclk, vco);
 
 	if (!skl_cdclk_wait_for_pcu_ready(dev_priv)) {
 		DRM_ERROR("failed to inform PCU about cdclk change\n");
@@ -5619,6 +5625,13 @@ static void skl_set_cdclk(struct drm_i915_private *dev_priv, int cdclk)
 		break;
 	}
 
+	if (dev_priv->skl_vco_freq != 0 &&
+	    dev_priv->skl_vco_freq != vco)
+		skl_dpll0_disable(dev_priv);
+
+	if (dev_priv->skl_vco_freq != vco)
+		skl_dpll0_enable(dev_priv, vco);
+
 	I915_WRITE(CDCLK_CTL, freq_select | skl_cdclk_decimal(cdclk));
 	POSTING_READ(CDCLK_CTL);
 
@@ -5641,26 +5654,21 @@ void skl_uninit_cdclk(struct drm_i915_private *dev_priv)
 	if (I915_READ(DBUF_CTL) & DBUF_POWER_STATE)
 		DRM_ERROR("DBuf power disable timeout\n");
 
-	skl_dpll0_disable(dev_priv);
+	skl_set_cdclk(dev_priv, 24000, 0);
 }
 
 void skl_init_cdclk(struct drm_i915_private *dev_priv)
 {
-	unsigned int cdclk;
-
 	/* DPLL0 not enabled (happens on early BIOS versions) */
-	if (!(I915_READ(LCPLL1_CTL) & LCPLL_PLL_ENABLE)) {
-		/* enable DPLL0 */
-		if (dev_priv->skl_vco_freq != 8640)
-			dev_priv->skl_vco_freq = 8100;
-		skl_dpll0_enable(dev_priv, dev_priv->skl_vco_freq);
-		cdclk = skl_calc_cdclk(0, dev_priv->skl_vco_freq);
-	} else {
-		cdclk = dev_priv->cdclk_freq;
-	}
+	if (dev_priv->skl_vco_freq == 0) {
+		int cdclk, vco;
 
-	/* set CDCLK to the lowest frequency, Modeset follows */
-	skl_set_cdclk(dev_priv, cdclk);
+		/* set CDCLK to the lowest frequency, Modeset follows */
+		vco = 8100;
+		cdclk = skl_calc_cdclk(0, vco);
+
+		skl_set_cdclk(dev_priv, cdclk, vco);
+	}
 
 	/* enable DBUF power */
 	I915_WRITE(DBUF_CTL, I915_READ(DBUF_CTL) | DBUF_POWER_REQUEST);
@@ -9703,16 +9711,12 @@ static int skl_modeset_calc_cdclk(struct drm_atomic_state *state)
 
 static void skl_modeset_commit_cdclk(struct drm_atomic_state *old_state)
 {
-	struct drm_device *dev = old_state->dev;
-	struct drm_i915_private *dev_priv = dev->dev_private;
-	unsigned int req_cdclk = to_intel_atomic_state(old_state)->dev_cdclk;
-
-	/*
-	 * FIXME disable/enable PLL should wrap set_cdclk()
-	 */
-	skl_set_cdclk(dev_priv, req_cdclk);
+	struct drm_i915_private *dev_priv = to_i915(old_state->dev);
+	struct intel_atomic_state *intel_state = to_intel_atomic_state(old_state);
+	unsigned int req_cdclk = intel_state->dev_cdclk;
+	unsigned int req_vco = intel_state->cdclk_pll_vco;
 
-	dev_priv->skl_vco_freq = to_intel_atomic_state(old_state)->cdclk_pll_vco;
+	skl_set_cdclk(dev_priv, req_cdclk, req_vco);
 }
 
 static int haswell_crtc_compute_clock(struct intel_crtc *crtc,