Revert "drm/i915: Disable SSC for outputs other than LVDS or DP"

This reverts commit 633f2ea2 and the
attempted fix dcbe6f2b.

There is a single clock source used for both SSC (some LVDS and DP) and
non-SSC (VGA, DVI) outputs. So we need to be careful to only enable SSC
as necessary. However, fiddling with DREFCLK was causing DP links to be
dropped and we do not have a fix ready, so revert.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_drv.h

@@ -346,7 +346,6 @@ typedef struct drm_i915_private {
 	unsigned int lvds_vbt:1;
 	unsigned int int_crt_support:1;
 	unsigned int lvds_use_ssc:1;
-	unsigned int display_clock_mode:1;
 	int lvds_ssc_freq;
 	struct {
 		int rate;

drivers/gpu/drm/i915/intel_bios.c

@@ -285,7 +285,6 @@ parse_general_features(struct drm_i915_private *dev_priv,
 		dev_priv->lvds_use_ssc = general->enable_ssc;
 		dev_priv->lvds_ssc_freq =
 			intel_bios_ssc_frequency(dev, general->ssc_freq);
-		dev_priv->display_clock_mode = general->display_clock_mode;
 	}
 }
 

drivers/gpu/drm/i915/intel_bios.h

@@ -120,9 +120,7 @@ struct bdb_general_features {
 	u8 ssc_freq:1;
 	u8 enable_lfp_on_override:1;
 	u8 disable_ssc_ddt:1;
-	u8 rsvd7:1;
-	u8 display_clock_mode:1;
-	u8 rsvd8:1; /* finish byte */
+	u8 rsvd8:3; /* finish byte */
 
         /* bits 3 */
 	u8 disable_smooth_vision:1;

drivers/gpu/drm/i915/intel_display.c

@@ -4506,81 +4506,6 @@ static inline bool intel_panel_use_ssc(struct drm_i915_private *dev_priv)
 	return dev_priv->lvds_use_ssc && i915_panel_use_ssc;
 }
 
-static void intel_update_dref(struct drm_i915_private *dev_priv)
-{
-	struct drm_device *dev = dev_priv->dev;
-	struct drm_mode_config *mode_config = &dev->mode_config;
-	struct intel_encoder *encoder;
-	struct drm_crtc *crtc;
-	u32 temp;
-	bool lvds_on = false, edp_on = false, pch_edp_on = false, other_on = false;
-
-	list_for_each_entry(encoder, &mode_config->encoder_list, base.head) {
-		crtc = encoder->base.crtc;
-
-		if (!crtc || !crtc->enabled)
-			continue;
-
-		switch (encoder->type) {
-		case INTEL_OUTPUT_LVDS:
-			lvds_on = true;
-			break;
-		case INTEL_OUTPUT_EDP:
-			edp_on = true;
-			if (!pch_edp_on)
-				pch_edp_on = intel_encoder_is_pch_edp(&encoder->base);
-			break;
-		default:
-			other_on = true;
-			break;
-		}
-	}
-
-	/*XXX BIOS treats 16:31 as a mask for 0:15 */
-
-	temp = I915_READ(PCH_DREF_CONTROL);
-
-	/* First clear the current state for output switching */
-	temp &= ~DREF_SSC1_ENABLE;
-	temp &= ~DREF_SSC4_ENABLE;
-	temp &= ~DREF_SUPERSPREAD_SOURCE_MASK;
-	temp &= ~DREF_NONSPREAD_SOURCE_MASK;
-	temp &= ~DREF_SSC_SOURCE_MASK;
-	temp &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
-	I915_WRITE(PCH_DREF_CONTROL, temp);
-
-	POSTING_READ(PCH_DREF_CONTROL);
-	udelay(200);
-
-	if ((lvds_on || edp_on) && intel_panel_use_ssc(dev_priv)) {
-		temp |= DREF_SSC_SOURCE_ENABLE;
-		if (edp_on) {
-			if (!pch_edp_on) {
-				/* Enable CPU source on CPU attached eDP */
-				temp |= DREF_CPU_SOURCE_OUTPUT_DOWNSPREAD;
-			} else {
-				/* Enable SSC on PCH eDP if needed */
-				temp |= DREF_SUPERSPREAD_SOURCE_ENABLE;
-			}
-			I915_WRITE(PCH_DREF_CONTROL, temp);
-		}
-		if (!dev_priv->display_clock_mode)
-			temp |= DREF_SSC1_ENABLE;
-	}
-
-	if (other_on && dev_priv->display_clock_mode)
-		temp |= DREF_NONSPREAD_CK505_ENABLE;
-	else if (other_on) {
-		temp |= DREF_NONSPREAD_SOURCE_ENABLE;
-		if (edp_on && !pch_edp_on)
-			temp |= DREF_CPU_SOURCE_OUTPUT_NONSPREAD;
-	}
-
-	I915_WRITE(PCH_DREF_CONTROL, temp);
-	POSTING_READ(PCH_DREF_CONTROL);
-	udelay(200);
-}
-
 static int intel_crtc_mode_set(struct drm_crtc *crtc,
 			       struct drm_display_mode *mode,
 			       struct drm_display_mode *adjusted_mode,
@@ -4806,8 +4731,46 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 	 * PCH B stepping, previous chipset stepping should be
 	 * ignoring this setting.
 	 */
-	if (HAS_PCH_SPLIT(dev))
-		intel_update_dref(dev_priv);
+	if (HAS_PCH_SPLIT(dev)) {
+		temp = I915_READ(PCH_DREF_CONTROL);
+		/* Always enable nonspread source */
+		temp &= ~DREF_NONSPREAD_SOURCE_MASK;
+		temp |= DREF_NONSPREAD_SOURCE_ENABLE;
+		temp &= ~DREF_SSC_SOURCE_MASK;
+		temp |= DREF_SSC_SOURCE_ENABLE;
+		I915_WRITE(PCH_DREF_CONTROL, temp);
+
+		POSTING_READ(PCH_DREF_CONTROL);
+		udelay(200);
+
+		if (has_edp_encoder) {
+			if (intel_panel_use_ssc(dev_priv)) {
+				temp |= DREF_SSC1_ENABLE;
+				I915_WRITE(PCH_DREF_CONTROL, temp);
+
+				POSTING_READ(PCH_DREF_CONTROL);
+				udelay(200);
+			}
+			temp &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
+
+			/* Enable CPU source on CPU attached eDP */
+			if (!intel_encoder_is_pch_edp(&has_edp_encoder->base)) {
+				if (intel_panel_use_ssc(dev_priv))
+					temp |= DREF_CPU_SOURCE_OUTPUT_DOWNSPREAD;
+				else
+					temp |= DREF_CPU_SOURCE_OUTPUT_NONSPREAD;
+			} else {
+				/* Enable SSC on PCH eDP if needed */
+				if (intel_panel_use_ssc(dev_priv)) {
+					DRM_ERROR("enabling SSC on PCH\n");
+					temp |= DREF_SUPERSPREAD_SOURCE_ENABLE;
+				}
+			}
+			I915_WRITE(PCH_DREF_CONTROL, temp);
+			POSTING_READ(PCH_DREF_CONTROL);
+			udelay(200);
+		}
+	}
 
 	if (IS_PINEVIEW(dev)) {
 		fp = (1 << clock.n) << 16 | clock.m1 << 8 | clock.m2;