drm/i915/cnl: Implement .set_cdclk() for CNL

Add support for changing the cdclk frequency on CNL. Again, quite
similar to BXT, but there are some annoying differences which means
trying to share more code might not be feasible:
* PLL ratio now lives in the PLL enable register
* pcode came from SKL, not from BXT

We support three cdclk frequencies: 168,336,528 Mhz. The first two
use the same PLL frequency, the last one uses a different one meaning
we once again may need to toggle the PLL off and on when changing
cdclk.

v2: Rebased by Rodrigo on top of Ville's cdclk rework.
v3: Respect order of set_ bellow get_ (Ville)
v4: Added __attribute__((unused)) to avoid broken compilation with Werror.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1497047175-27250-2-git-send-email-rodrigo.vivi@intel.com

drivers/gpu/drm/i915/intel_cdclk.c

@@ -1452,6 +1452,112 @@ static void cnl_get_cdclk(struct drm_i915_private *dev_priv,
 	cdclk_state->cdclk = DIV_ROUND_CLOSEST(cdclk_state->vco, div);
 }
 
+static void cnl_cdclk_pll_disable(struct drm_i915_private *dev_priv)
+{
+	u32 val;
+
+	val = I915_READ(BXT_DE_PLL_ENABLE);
+	val &= ~BXT_DE_PLL_PLL_ENABLE;
+	I915_WRITE(BXT_DE_PLL_ENABLE, val);
+
+	/* Timeout 200us */
+	if (wait_for((I915_READ(BXT_DE_PLL_ENABLE) & BXT_DE_PLL_LOCK) == 0, 1))
+		DRM_ERROR("timout waiting for CDCLK PLL unlock\n");
+
+	dev_priv->cdclk.hw.vco = 0;
+}
+
+static void cnl_cdclk_pll_enable(struct drm_i915_private *dev_priv, int vco)
+{
+	int ratio = DIV_ROUND_CLOSEST(vco, dev_priv->cdclk.hw.ref);
+	u32 val;
+
+	val = CNL_CDCLK_PLL_RATIO(ratio);
+	I915_WRITE(BXT_DE_PLL_ENABLE, val);
+
+	val |= BXT_DE_PLL_PLL_ENABLE;
+	I915_WRITE(BXT_DE_PLL_ENABLE, val);
+
+	/* Timeout 200us */
+	if (wait_for((I915_READ(BXT_DE_PLL_ENABLE) & BXT_DE_PLL_LOCK) != 0, 1))
+		DRM_ERROR("timout waiting for CDCLK PLL lock\n");
+
+	dev_priv->cdclk.hw.vco = vco;
+}
+
+__attribute__((unused))
+static void cnl_set_cdclk(struct drm_i915_private *dev_priv,
+			  const struct intel_cdclk_state *cdclk_state)
+{
+	int cdclk = cdclk_state->cdclk;
+	int vco = cdclk_state->vco;
+	u32 val, divider, pcu_ack;
+	int ret;
+
+	mutex_lock(&dev_priv->rps.hw_lock);
+	ret = skl_pcode_request(dev_priv, SKL_PCODE_CDCLK_CONTROL,
+				SKL_CDCLK_PREPARE_FOR_CHANGE,
+				SKL_CDCLK_READY_FOR_CHANGE,
+				SKL_CDCLK_READY_FOR_CHANGE, 3);
+	mutex_unlock(&dev_priv->rps.hw_lock);
+	if (ret) {
+		DRM_ERROR("Failed to inform PCU about cdclk change (%d)\n",
+			  ret);
+		return;
+	}
+
+	/* cdclk = vco / 2 / div{1,2} */
+	switch (DIV_ROUND_CLOSEST(vco, cdclk)) {
+	case 4:
+		divider = BXT_CDCLK_CD2X_DIV_SEL_2;
+		break;
+	case 2:
+		divider = BXT_CDCLK_CD2X_DIV_SEL_1;
+		break;
+	default:
+		WARN_ON(cdclk != dev_priv->cdclk.hw.ref);
+		WARN_ON(vco != 0);
+
+		divider = BXT_CDCLK_CD2X_DIV_SEL_1;
+		break;
+	}
+
+	switch (cdclk) {
+	case 528000:
+		pcu_ack = 2;
+		break;
+	case 336000:
+		pcu_ack = 1;
+		break;
+	case 168000:
+	default:
+		pcu_ack = 0;
+		break;
+	}
+
+	if (dev_priv->cdclk.hw.vco != 0 &&
+	    dev_priv->cdclk.hw.vco != vco)
+		cnl_cdclk_pll_disable(dev_priv);
+
+	if (dev_priv->cdclk.hw.vco != vco)
+		cnl_cdclk_pll_enable(dev_priv, vco);
+
+	val = divider | skl_cdclk_decimal(cdclk);
+	/*
+	 * FIXME if only the cd2x divider needs changing, it could be done
+	 * without shutting off the pipe (if only one pipe is active).
+	 */
+	val |= BXT_CDCLK_CD2X_PIPE_NONE;
+	I915_WRITE(CDCLK_CTL, val);
+
+	/* inform PCU of the change */
+	mutex_lock(&dev_priv->rps.hw_lock);
+	sandybridge_pcode_write(dev_priv, SKL_PCODE_CDCLK_CONTROL, pcu_ack);
+	mutex_unlock(&dev_priv->rps.hw_lock);
+
+	intel_update_cdclk(dev_priv);
+}
+
 /**
  * intel_cdclk_state_compare - Determine if two CDCLK states differ
  * @a: first CDCLK state