drm/i915: Actually read out DPLL0 vco on skl from hardware

Currently we're trying to guess which lcpll vco frequency is used
use based on the cdclk. That doesn't work for cdclk==540 since
both vco frequencies can generate a 540 Mhz output. Let's stop
guessing and just read the actual vco frequency from the
hardware.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1463172100-24715-6-git-send-email-ville.syrjala@linux.intel.comReviewed-by: Imre Deak <imre.deak@intel.com>

drivers/gpu/drm/i915/intel_display.c

@@ -5471,31 +5471,35 @@ static int skl_calc_cdclk(int max_pixclk, int vco)
 	}
 }
 
-static const struct skl_cdclk_entry {
-	unsigned int freq;
-	unsigned int vco;
-} skl_cdclk_frequencies[] = {
-	{ .freq = 308570, .vco = 8640 },
-	{ .freq = 337500, .vco = 8100 },
-	{ .freq = 432000, .vco = 8640 },
-	{ .freq = 450000, .vco = 8100 },
-	{ .freq = 540000, .vco = 8100 },
-	{ .freq = 617140, .vco = 8640 },
-	{ .freq = 675000, .vco = 8100 },
-};
-
-unsigned int skl_cdclk_get_vco(unsigned int freq)
+static void
+skl_dpll0_update(struct drm_i915_private *dev_priv)
 {
-	unsigned int i;
-
-	for (i = 0; i < ARRAY_SIZE(skl_cdclk_frequencies); i++) {
-		const struct skl_cdclk_entry *e = &skl_cdclk_frequencies[i];
+	u32 val;
 
-		if (e->freq == freq)
-			return e->vco;
+	val = I915_READ(LCPLL1_CTL);
+	if ((val & LCPLL_PLL_ENABLE) == 0) {
+		dev_priv->skl_vco_freq = 0;
+		return;
 	}
 
-	return 8100;
+	val = I915_READ(DPLL_CTRL1);
+
+	switch (val & DPLL_CTRL1_LINK_RATE_MASK(SKL_DPLL0)) {
+	case DPLL_CTRL1_LINK_RATE(DPLL_CTRL1_LINK_RATE_810, SKL_DPLL0):
+	case DPLL_CTRL1_LINK_RATE(DPLL_CTRL1_LINK_RATE_1350, SKL_DPLL0):
+	case DPLL_CTRL1_LINK_RATE(DPLL_CTRL1_LINK_RATE_1620, SKL_DPLL0):
+	case DPLL_CTRL1_LINK_RATE(DPLL_CTRL1_LINK_RATE_2700, SKL_DPLL0):
+		dev_priv->skl_vco_freq = 8100;
+		break;
+	case DPLL_CTRL1_LINK_RATE(DPLL_CTRL1_LINK_RATE_1080, SKL_DPLL0):
+	case DPLL_CTRL1_LINK_RATE(DPLL_CTRL1_LINK_RATE_2160, SKL_DPLL0):
+		dev_priv->skl_vco_freq = 8640;
+		break;
+	default:
+		MISSING_CASE(val & DPLL_CTRL1_LINK_RATE_MASK(SKL_DPLL0));
+		dev_priv->skl_vco_freq = 0;
+		break;
+	}
 }
 
 static void
@@ -6540,43 +6544,40 @@ static int intel_crtc_compute_config(struct intel_crtc *crtc,
 static int skylake_get_display_clock_speed(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = to_i915(dev);
-	uint32_t lcpll1 = I915_READ(LCPLL1_CTL);
-	uint32_t cdctl = I915_READ(CDCLK_CTL);
-	uint32_t linkrate;
+	uint32_t cdctl;
 
-	if (!(lcpll1 & LCPLL_PLL_ENABLE))
-		return 24000; /* 24MHz is the cd freq with NSSC ref */
+	skl_dpll0_update(dev_priv);
 
-	if ((cdctl & CDCLK_FREQ_SEL_MASK) == CDCLK_FREQ_540)
-		return 540000;
+	if (dev_priv->skl_vco_freq == 0)
+		return 24000; /* 24MHz is the cd freq with NSSC ref */
 
-	linkrate = (I915_READ(DPLL_CTRL1) &
-		    DPLL_CTRL1_LINK_RATE_MASK(SKL_DPLL0)) >> 1;
+	cdctl = I915_READ(CDCLK_CTL);
 
-	if (linkrate == DPLL_CTRL1_LINK_RATE_2160 ||
-	    linkrate == DPLL_CTRL1_LINK_RATE_1080) {
-		/* vco 8640 */
+	if (dev_priv->skl_vco_freq == 8640) {
 		switch (cdctl & CDCLK_FREQ_SEL_MASK) {
 		case CDCLK_FREQ_450_432:
 			return 432000;
 		case CDCLK_FREQ_337_308:
 			return 308570;
+		case CDCLK_FREQ_540:
+			return 540000;
 		case CDCLK_FREQ_675_617:
 			return 617140;
 		default:
-			WARN(1, "Unknown cd freq selection\n");
+			MISSING_CASE(cdctl & CDCLK_FREQ_SEL_MASK);
 		}
 	} else {
-		/* vco 8100 */
 		switch (cdctl & CDCLK_FREQ_SEL_MASK) {
 		case CDCLK_FREQ_450_432:
 			return 450000;
 		case CDCLK_FREQ_337_308:
 			return 337500;
+		case CDCLK_FREQ_540:
+			return 540000;
 		case CDCLK_FREQ_675_617:
 			return 675000;
 		default:
-			WARN(1, "Unknown cd freq selection\n");
+			MISSING_CASE(cdctl & CDCLK_FREQ_SEL_MASK);
 		}
 	}
 

drivers/gpu/drm/i915/intel_dpll_mgr.c

@@ -1633,14 +1633,8 @@ static void intel_ddi_pll_init(struct drm_device *dev)
 	uint32_t val = I915_READ(LCPLL_CTL);
 
 	if (IS_SKYLAKE(dev) || IS_KABYLAKE(dev)) {
-		int cdclk_freq;
-
-		cdclk_freq = dev_priv->display.get_display_clock_speed(dev);
-		dev_priv->skl_vco_freq = skl_cdclk_get_vco(cdclk_freq);
 		if (skl_sanitize_cdclk(dev_priv))
 			DRM_DEBUG_KMS("Sanitized cdclk programmed by pre-os\n");
-		if (!(I915_READ(LCPLL1_CTL) & LCPLL_PLL_ENABLE))
-			DRM_ERROR("LCPLL1 is disabled\n");
 	} else if (!IS_BROXTON(dev_priv)) {
 		/*
 		 * The LCPLL register should be turned on by the BIOS. For now