drm/i915/skl: If needed sanitize bios programmed cdclk

Especially in cases where pre-os does not enable display, cdclk might
not be in sane state. During sanitization initialize cdclk with maximum
value till we get dynamic cdclk support.

v2: Check if BIOS programmed correctly rather than always calling init
    - Do validation of programmed cdctl and what it is expected
    - Only do slk_init_cdclk if validation failed else reuse BIOS
      programmed value

v3: Move the validation logic in a separate sanitize function (Ville)

v4: No need to check LCPLL after sanitize and use max_cdclk_freq instead
    of hardcoded value (Ville)

Cc: Imre Deak <imre.deak@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1445344992-14658-1-git-send-email-shobhit.kumar@intel.comReviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_ddi.c

@@ -2949,8 +2949,8 @@ void intel_ddi_pll_init(struct drm_device *dev)
 
 		cdclk_freq = dev_priv->display.get_display_clock_speed(dev);
 		dev_priv->skl_boot_cdclk = cdclk_freq;
-		if (!(I915_READ(LCPLL1_CTL) & LCPLL_PLL_ENABLE))
-			DRM_ERROR("LCPLL1 is disabled\n");
+		if (skl_sanitize_cdclk(dev_priv))
+			DRM_DEBUG_KMS("Sanitized cdclk programmed by pre-os\n");
 		else
 			intel_display_power_get(dev_priv, POWER_DOMAIN_PLLS);
 	} else if (IS_BROXTON(dev)) {

drivers/gpu/drm/i915/intel_display.c

@@ -5760,6 +5760,37 @@ void skl_init_cdclk(struct drm_i915_private *dev_priv)
 		DRM_ERROR("DBuf power enable timeout\n");
 }
 
+int skl_sanitize_cdclk(struct drm_i915_private *dev_priv)
+{
+	uint32_t lcpll1 = I915_READ(LCPLL1_CTL);
+	uint32_t cdctl = I915_READ(CDCLK_CTL);
+	int freq = dev_priv->skl_boot_cdclk;
+
+	/* Is PLL enabled and locked ? */
+	if (!((lcpll1 & LCPLL_PLL_ENABLE) && (lcpll1 & LCPLL_PLL_LOCK)))
+		goto sanitize;
+
+	/* DPLL okay; verify the cdclock
+	 *
+	 * Noticed in some instances that the freq selection is correct but
+	 * decimal part is programmed wrong from BIOS where pre-os does not
+	 * enable display. Verify the same as well.
+	 */
+	if (cdctl == ((cdctl & CDCLK_FREQ_SEL_MASK) | skl_cdclk_decimal(freq)))
+		/* All well; nothing to sanitize */
+		return false;
+sanitize:
+	/*
+	 * As of now initialize with max cdclk till
+	 * we get dynamic cdclk support
+	 * */
+	dev_priv->skl_boot_cdclk = dev_priv->max_cdclk_freq;
+	skl_init_cdclk(dev_priv);
+
+	/* we did have to sanitize */
+	return true;
+}
+
 /* Adjust CDclk dividers to allow high res or save power if possible */
 static void valleyview_set_cdclk(struct drm_device *dev, int cdclk)
 {

drivers/gpu/drm/i915/intel_drv.h

@@ -1151,6 +1151,7 @@ void broxton_ddi_phy_uninit(struct drm_device *dev);
 void bxt_enable_dc9(struct drm_i915_private *dev_priv);
 void bxt_disable_dc9(struct drm_i915_private *dev_priv);
 void skl_init_cdclk(struct drm_i915_private *dev_priv);
+int skl_sanitize_cdclk(struct drm_i915_private *dev_priv);
 void skl_uninit_cdclk(struct drm_i915_private *dev_priv);
 void skl_enable_dc6(struct drm_i915_private *dev_priv);
 void skl_disable_dc6(struct drm_i915_private *dev_priv);