Revert "drm/i915/ilk: Don't disable SSC source if it's in use"

This reverts commit f165d283.

It breaks one of our CI systems. Quoting from Ville:

[   13.100979] [drm:ironlake_init_pch_refclk] has_panel 1 has_lvds 1 has_ck505 0 using_ssc_source 1
[   13.101413] ------------[ cut here ]------------
[   13.101429] kernel BUG at drivers/gpu/drm/i915/intel_display.c:8528!

"which is the 'BUG_ON(val != final)' at the end of ironlake_init_pch_refclk()."

Cc: stable@vger.kernel.org
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Lyude <cpaul@redhat.com>
Cc: marius.c.vlad@intel.com
References: https://www.spinics.net/lists/dri-devel/msg109557.htmlAcked-by: Lyude <cpaul@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

drivers/gpu/drm/i915/intel_display.c

@@ -8361,14 +8361,12 @@ static void ironlake_init_pch_refclk(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_encoder *encoder;
-	int i;
 	u32 val, final;
 	bool has_lvds = false;
 	bool has_cpu_edp = false;
 	bool has_panel = false;
 	bool has_ck505 = false;
 	bool can_ssc = false;
-	bool using_ssc_source = false;
 
 	/* We need to take the global config into account */
 	for_each_intel_encoder(dev, encoder) {
@@ -8395,22 +8393,8 @@ static void ironlake_init_pch_refclk(struct drm_device *dev)
 		can_ssc = true;
 	}
 
-	/* Check if any DPLLs are using the SSC source */
-	for (i = 0; i < dev_priv->num_shared_dpll; i++) {
-		u32 temp = I915_READ(PCH_DPLL(i));
-
-		if (!(temp & DPLL_VCO_ENABLE))
-			continue;
-
-		if ((temp & PLL_REF_INPUT_MASK) ==
-		    PLLB_REF_INPUT_SPREADSPECTRUMIN) {
-			using_ssc_source = true;
-			break;
-		}
-	}
-
-	DRM_DEBUG_KMS("has_panel %d has_lvds %d has_ck505 %d using_ssc_source %d\n",
-		      has_panel, has_lvds, has_ck505, using_ssc_source);
+	DRM_DEBUG_KMS("has_panel %d has_lvds %d has_ck505 %d\n",
+		      has_panel, has_lvds, has_ck505);
 
 	/* Ironlake: try to setup display ref clock before DPLL
 	 * enabling. This is only under driver's control after
@@ -8430,12 +8414,9 @@ static void ironlake_init_pch_refclk(struct drm_device *dev)
 	else
 		final |= DREF_NONSPREAD_SOURCE_ENABLE;
 
-	final &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
-
-	if (!using_ssc_source) {
 	final &= ~DREF_SSC_SOURCE_MASK;
+	final &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
 	final &= ~DREF_SSC1_ENABLE;
-	}
 
 	if (has_panel) {
 		final |= DREF_SSC_SOURCE_ENABLE;
@@ -8498,7 +8479,7 @@ static void ironlake_init_pch_refclk(struct drm_device *dev)
 		POSTING_READ(PCH_DREF_CONTROL);
 		udelay(200);
 	} else {
-		DRM_DEBUG_KMS("Disabling CPU source output\n");
+		DRM_DEBUG_KMS("Disabling SSC entirely\n");
 
 		val &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
 
@@ -8509,9 +8490,6 @@ static void ironlake_init_pch_refclk(struct drm_device *dev)
 		POSTING_READ(PCH_DREF_CONTROL);
 		udelay(200);
 
-		if (!using_ssc_source) {
-			DRM_DEBUG_KMS("Disabling SSC source\n");
-
 		/* Turn off the SSC source */
 		val &= ~DREF_SSC_SOURCE_MASK;
 		val |= DREF_SSC_SOURCE_DISABLE;
@@ -8523,7 +8501,6 @@ static void ironlake_init_pch_refclk(struct drm_device *dev)
 		POSTING_READ(PCH_DREF_CONTROL);
 		udelay(200);
 	}
-	}
 
 	BUG_ON(val != final);
 }