drm/i915: Keep track of preferred cdclk vco frequency on SKL

Now that skl_vco_freq tracks the actual DPLL0 vco frequency, we'll need
something that keeps track of which vco frequency we want to use in case
the current vco is 0. This would be important across supend/resume since
we'll disable DPLL0 around those parts.

We'll also update our idea of max cdclk/dotclock when the preferred
vco changes. That could happen if out initial guess was wrong, and
later eDP would force us to change it. One issue here could be that
changing the max dotclock could cause our mode list to change during
next time the displays get probed. But I don't see a good way to avoid
that, except perhaps by allowing either vco frequency to be used as
needed. But the docs suggest that such usage wasn't really inteded.

Also need to make sure we don't update our max_cdclk value before we
have a preferred vco value, which means moving that to happen after
the cdclk sanitation.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1463172100-24715-9-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com>

drivers/gpu/drm/i915/i915_drv.h

@@ -1816,6 +1816,7 @@ struct drm_i915_private {
 
 	unsigned int fsb_freq, mem_freq, is_ddr3;
 	unsigned int skl_vco_freq;
+	unsigned int skl_preferred_vco_freq;
 	unsigned int cdclk_freq, max_cdclk_freq, atomic_cdclk_freq;
 	unsigned int max_dotclk_freq;
 	unsigned int rawclk_freq;

drivers/gpu/drm/i915/intel_display.c

@@ -5185,21 +5185,34 @@ static int intel_compute_max_dotclk(struct drm_i915_private *dev_priv)
 		return max_cdclk_freq*90/100;
 }
 
+static int skl_calc_cdclk(int max_pixclk, int vco);
+
 static void intel_update_max_cdclk(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
 	if (IS_SKYLAKE(dev) || IS_KABYLAKE(dev)) {
 		u32 limit = I915_READ(SKL_DFSM) & SKL_DFSM_CDCLK_LIMIT_MASK;
+		int max_cdclk, vco;
+
+		vco = dev_priv->skl_preferred_vco_freq;
+		WARN_ON(vco != 8100 && vco != 8640);
 
+		/*
+		 * Use the lower (vco 8640) cdclk values as a
+		 * first guess. skl_calc_cdclk() will correct it
+		 * if the preferred vco is 8100 instead.
+		 */
 		if (limit == SKL_DFSM_CDCLK_LIMIT_675)
-			dev_priv->max_cdclk_freq = 675000;
+			max_cdclk = 617140;
 		else if (limit == SKL_DFSM_CDCLK_LIMIT_540)
-			dev_priv->max_cdclk_freq = 540000;
+			max_cdclk = 540000;
 		else if (limit == SKL_DFSM_CDCLK_LIMIT_450)
-			dev_priv->max_cdclk_freq = 450000;
+			max_cdclk = 432000;
 		else
-			dev_priv->max_cdclk_freq = 337500;
+			max_cdclk = 308570;
+
+		dev_priv->max_cdclk_freq = skl_calc_cdclk(max_cdclk, vco);
 	} else if (IS_BROXTON(dev)) {
 		dev_priv->max_cdclk_freq = 624000;
 	} else if (IS_BROADWELL(dev))  {
@@ -5256,9 +5269,6 @@ static void intel_update_cdclk(struct drm_device *dev)
 	 */
 	if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
 		I915_WRITE(GMBUSFREQ_VLV, DIV_ROUND_UP(dev_priv->cdclk_freq, 1000));
-
-	if (dev_priv->max_cdclk_freq == 0)
-		intel_update_max_cdclk(dev);
 }
 
 /* convert from kHz to .1 fixpoint MHz with -1MHz offset */
@@ -5507,12 +5517,24 @@ skl_dpll0_update(struct drm_i915_private *dev_priv)
 	}
 }
 
+void skl_set_preferred_cdclk_vco(struct drm_i915_private *dev_priv, int vco)
+{
+	bool changed = dev_priv->skl_preferred_vco_freq != vco;
+
+	dev_priv->skl_preferred_vco_freq = vco;
+
+	if (changed)
+		intel_update_max_cdclk(dev_priv->dev);
+}
+
 static void
 skl_dpll0_enable(struct drm_i915_private *dev_priv, int vco)
 {
 	int min_cdclk = skl_calc_cdclk(0, vco);
 	u32 val;
 
+	WARN_ON(vco != 8100 && vco != 8640);
+
 	/* select the minimum CDCLK before enabling DPLL 0 */
 	val = CDCLK_FREQ_337_308 | skl_cdclk_decimal(min_cdclk);
 	I915_WRITE(CDCLK_CTL, val);
@@ -5548,6 +5570,9 @@ skl_dpll0_enable(struct drm_i915_private *dev_priv, int vco)
 		DRM_ERROR("DPLL0 not locked\n");
 
 	dev_priv->skl_vco_freq = vco;
+
+	/* We'll want to keep using the current vco from now on. */
+	skl_set_preferred_cdclk_vco(dev_priv, vco);
 }
 
 static void
@@ -5664,7 +5689,9 @@ void skl_init_cdclk(struct drm_i915_private *dev_priv)
 		int cdclk, vco;
 
 		/* set CDCLK to the lowest frequency, Modeset follows */
-		vco = 8100;
+		vco = dev_priv->skl_preferred_vco_freq;
+		if (vco == 0)
+			vco = 8100;
 		cdclk = skl_calc_cdclk(0, vco);
 
 		skl_set_cdclk(dev_priv, cdclk, vco);
@@ -12651,6 +12678,8 @@ static int intel_modeset_checks(struct drm_atomic_state *state)
 	if (dev_priv->display.modeset_calc_cdclk) {
 		if (!intel_state->cdclk_pll_vco)
 			intel_state->cdclk_pll_vco = dev_priv->skl_vco_freq;
+		if (!intel_state->cdclk_pll_vco)
+			intel_state->cdclk_pll_vco = dev_priv->skl_preferred_vco_freq;
 
 		ret = dev_priv->display.modeset_calc_cdclk(state);
 		if (ret < 0)
@@ -14905,6 +14934,9 @@ void intel_modeset_init(struct drm_device *dev)
 
 	intel_shared_dpll_init(dev);
 
+	if (dev_priv->max_cdclk_freq == 0)
+		intel_update_max_cdclk(dev);
+
 	/* Just disable it once at startup */
 	i915_disable_vga(dev);
 	intel_setup_outputs(dev);

drivers/gpu/drm/i915/intel_dpll_mgr.c

@@ -1635,6 +1635,11 @@ static void intel_ddi_pll_init(struct drm_device *dev)
 	if (IS_SKYLAKE(dev) || IS_KABYLAKE(dev)) {
 		if (skl_sanitize_cdclk(dev_priv))
 			DRM_DEBUG_KMS("Sanitized cdclk programmed by pre-os\n");
+
+		/* We'll want to keep using the current vco from now on */
+		if (dev_priv->skl_vco_freq != 0)
+			skl_set_preferred_cdclk_vco(dev_priv,
+						    dev_priv->skl_vco_freq);
 	} else if (!IS_BROXTON(dev_priv)) {
 		/*
 		 * The LCPLL register should be turned on by the BIOS. For now

drivers/gpu/drm/i915/intel_drv.h

@@ -1143,6 +1143,7 @@ void i915_audio_component_init(struct drm_i915_private *dev_priv);
 void i915_audio_component_cleanup(struct drm_i915_private *dev_priv);
 
 /* intel_display.c */
+void skl_set_preferred_cdclk_vco(struct drm_i915_private *dev_priv, int vco);
 void intel_update_rawclk(struct drm_i915_private *dev_priv);
 int vlv_get_cck_clock(struct drm_i915_private *dev_priv,
 		      const char *name, u32 reg, int ref_freq);