drm/i915: Add a module option to override the use of SSC

In order to workaround the issue with LVDS not working on the Lenovo
U160 apparently due to using the wrong SSC frequency, add an option to
disable SSC.

Suggested-by: Lukács, Árpád <lukacs.arpad@gmail.com>
Bugzillla: https://bugs.freedesktop.org/show_bug.cgi?id=32748
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org

drivers/gpu/drm/i915/i915_drv.c

@@ -49,6 +49,9 @@ module_param_named(powersave, i915_powersave, int, 0600);
 unsigned int i915_lvds_downclock = 0;
 module_param_named(lvds_downclock, i915_lvds_downclock, int, 0400);
 
+unsigned int i915_panel_use_ssc = 1;
+module_param_named(lvds_use_ssc, i915_panel_use_ssc, int, 0600);
+
 bool i915_try_reset = true;
 module_param_named(reset, i915_try_reset, bool, 0600);
 

drivers/gpu/drm/i915/i915_drv.h

@@ -954,6 +954,7 @@ extern int i915_max_ioctl;
 extern unsigned int i915_fbpercrtc;
 extern unsigned int i915_powersave;
 extern unsigned int i915_lvds_downclock;
+extern unsigned int i915_panel_use_ssc;
 
 extern int i915_suspend(struct drm_device *dev, pm_message_t state);
 extern int i915_resume(struct drm_device *dev);

drivers/gpu/drm/i915/intel_bios.c

@@ -264,17 +264,12 @@ parse_general_features(struct drm_i915_private *dev_priv,
 		dev_priv->int_crt_support = general->int_crt_support;
 		dev_priv->lvds_use_ssc = general->enable_ssc;
 
-		if (dev_priv->lvds_use_ssc) {
-			if (IS_I85X(dev))
-				dev_priv->lvds_ssc_freq =
-					general->ssc_freq ? 66 : 48;
-			else if (IS_GEN5(dev) || IS_GEN6(dev))
-				dev_priv->lvds_ssc_freq =
-					general->ssc_freq ? 100 : 120;
-			else
-				dev_priv->lvds_ssc_freq =
-					general->ssc_freq ? 100 : 96;
-		}
+		if (IS_I85X(dev))
+			dev_priv->lvds_ssc_freq = general->ssc_freq ? 66 : 48;
+		else if (IS_GEN5(dev) || IS_GEN6(dev))
+			dev_priv->lvds_ssc_freq = general->ssc_freq ? 100 : 120;
+		else
+			dev_priv->lvds_ssc_freq = general->ssc_freq ? 100 : 96;
 	}
 }
 

drivers/gpu/drm/i915/intel_display.c

@@ -3822,6 +3822,11 @@ static void intel_update_watermarks(struct drm_device *dev)
 				    sr_hdisplay, sr_htotal, pixel_size);
 }
 
+static inline bool intel_panel_use_ssc(struct drm_i915_private *dev_priv)
+{
+	return dev_priv->lvds_use_ssc && i915_panel_use_ssc;
+}
+
 static int intel_crtc_mode_set(struct drm_crtc *crtc,
 			       struct drm_display_mode *mode,
 			       struct drm_display_mode *adjusted_mode,
@@ -3884,7 +3889,7 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 		num_connectors++;
 	}
 
-	if (is_lvds && dev_priv->lvds_use_ssc && num_connectors < 2) {
+	if (is_lvds && intel_panel_use_ssc(dev_priv) && num_connectors < 2) {
 		refclk = dev_priv->lvds_ssc_freq * 1000;
 		DRM_DEBUG_KMS("using SSC reference clock of %d MHz\n",
 			      refclk / 1000);
@@ -4059,7 +4064,7 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 		udelay(200);
 
 		if (has_edp_encoder) {
-			if (dev_priv->lvds_use_ssc) {
+			if (intel_panel_use_ssc(dev_priv)) {
 				temp |= DREF_SSC1_ENABLE;
 				I915_WRITE(PCH_DREF_CONTROL, temp);
 
@@ -4070,13 +4075,13 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 
 			/* Enable CPU source on CPU attached eDP */
 			if (!intel_encoder_is_pch_edp(&has_edp_encoder->base)) {
-				if (dev_priv->lvds_use_ssc)
+				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 (dev_priv->lvds_use_ssc) {
+				if (intel_panel_use_ssc(dev_priv)) {
 					DRM_ERROR("enabling SSC on PCH\n");
 					temp |= DREF_SUPERSPREAD_SOURCE_ENABLE;
 				}
@@ -4104,7 +4109,7 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 		int factor = 21;
 
 		if (is_lvds) {
-			if ((dev_priv->lvds_use_ssc &&
+			if ((intel_panel_use_ssc(dev_priv) &&
 			     dev_priv->lvds_ssc_freq == 100) ||
 			    (I915_READ(PCH_LVDS) & LVDS_CLKB_POWER_MASK) == LVDS_CLKB_POWER_UP)
 				factor = 25;
@@ -4183,7 +4188,7 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 		/* XXX: just matching BIOS for now */
 		/*	dpll |= PLL_REF_INPUT_TVCLKINBC; */
 		dpll |= 3;
-	else if (is_lvds && dev_priv->lvds_use_ssc && num_connectors < 2)
+	else if (is_lvds && intel_panel_use_ssc(dev_priv) && num_connectors < 2)
 		dpll |= PLLB_REF_INPUT_SPREADSPECTRUMIN;
 	else
 		dpll |= PLL_REF_INPUT_DREFCLK;