drm/i915: Disable RC6 on Ironlake

The automatic powersaving feature is once again causing havoc, with 100%
reliable hangs on boot and resume on affected machines.
Reported-by: Francesco Allertsen <fallertsen@gmail.com>
Reported-by: Gui Rui <chaos.proton@gmail.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=28582Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_drv.c

@@ -46,6 +46,9 @@ module_param_named(fbpercrtc, i915_fbpercrtc, int, 0400);
 unsigned int i915_powersave = 1;
 module_param_named(powersave, i915_powersave, int, 0600);
 
+unsigned int i915_enable_rc6 = 0;
+module_param_named(i915_enable_rc6, i915_enable_rc6, int, 0600);
+
 unsigned int i915_lvds_downclock = 0;
 module_param_named(lvds_downclock, i915_lvds_downclock, int, 0400);
 
@@ -360,7 +363,7 @@ static int i915_drm_thaw(struct drm_device *dev)
 		/* Resume the modeset for every activated CRTC */
 		drm_helper_resume_force_mode(dev);
 
-		if (dev_priv->renderctx && dev_priv->pwrctx)
+		if (IS_IRONLAKE_M(dev))
 			ironlake_enable_rc6(dev);
 	}
 

drivers/gpu/drm/i915/i915_drv.h

@@ -958,6 +958,7 @@ extern unsigned int i915_fbpercrtc;
 extern unsigned int i915_powersave;
 extern unsigned int i915_lvds_downclock;
 extern unsigned int i915_panel_use_ssc;
+extern unsigned int i915_enable_rc6;
 
 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_display.c

@@ -6463,52 +6463,60 @@ void intel_enable_clock_gating(struct drm_device *dev)
 	}
 }
 
-void intel_disable_clock_gating(struct drm_device *dev)
+static void ironlake_teardown_rc6(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
 	if (dev_priv->renderctx) {
-		struct drm_i915_gem_object *obj = dev_priv->renderctx;
-
-		I915_WRITE(CCID, 0);
-		POSTING_READ(CCID);
-
-		i915_gem_object_unpin(obj);
-		drm_gem_object_unreference(&obj->base);
+		i915_gem_object_unpin(dev_priv->renderctx);
+		drm_gem_object_unreference(&dev_priv->renderctx->base);
 		dev_priv->renderctx = NULL;
 	}
 
 	if (dev_priv->pwrctx) {
-		struct drm_i915_gem_object *obj = dev_priv->pwrctx;
+		i915_gem_object_unpin(dev_priv->pwrctx);
+		drm_gem_object_unreference(&dev_priv->pwrctx->base);
+		dev_priv->pwrctx = NULL;
+	}
+}
+
+static void ironlake_disable_rc6(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	if (I915_READ(PWRCTXA)) {
+		/* Wake the GPU, prevent RC6, then restore RSTDBYCTL */
+		I915_WRITE(RSTDBYCTL, I915_READ(RSTDBYCTL) | RCX_SW_EXIT);
+		wait_for(((I915_READ(RSTDBYCTL) & RSX_STATUS_MASK) == RSX_STATUS_ON),
+			 50);
 
 		I915_WRITE(PWRCTXA, 0);
 		POSTING_READ(PWRCTXA);
 
-		i915_gem_object_unpin(obj);
-		drm_gem_object_unreference(&obj->base);
-		dev_priv->pwrctx = NULL;
+		I915_WRITE(RSTDBYCTL, I915_READ(RSTDBYCTL) & ~RCX_SW_EXIT);
+		POSTING_READ(RSTDBYCTL);
 	}
+
+	ironlake_disable_rc6(dev);
 }
 
-static void ironlake_disable_rc6(struct drm_device *dev)
+static int ironlake_setup_rc6(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	/* Wake the GPU, prevent RC6, then restore RSTDBYCTL */
-	I915_WRITE(RSTDBYCTL, I915_READ(RSTDBYCTL) | RCX_SW_EXIT);
-	wait_for(((I915_READ(RSTDBYCTL) & RSX_STATUS_MASK) == RSX_STATUS_ON),
-		 10);
-	POSTING_READ(CCID);
-	I915_WRITE(PWRCTXA, 0);
-	POSTING_READ(PWRCTXA);
-	I915_WRITE(RSTDBYCTL, I915_READ(RSTDBYCTL) & ~RCX_SW_EXIT);
-	POSTING_READ(RSTDBYCTL);
-	i915_gem_object_unpin(dev_priv->renderctx);
-	drm_gem_object_unreference(&dev_priv->renderctx->base);
-	dev_priv->renderctx = NULL;
-	i915_gem_object_unpin(dev_priv->pwrctx);
-	drm_gem_object_unreference(&dev_priv->pwrctx->base);
-	dev_priv->pwrctx = NULL;
+	if (dev_priv->renderctx == NULL)
+		dev_priv->renderctx = intel_alloc_context_page(dev);
+	if (!dev_priv->renderctx)
+		return -ENOMEM;
+
+	if (dev_priv->pwrctx == NULL)
+		dev_priv->pwrctx = intel_alloc_context_page(dev);
+	if (!dev_priv->pwrctx) {
+		ironlake_teardown_rc6(dev);
+		return -ENOMEM;
+	}
+
+	return 0;
 }
 
 void ironlake_enable_rc6(struct drm_device *dev)
@@ -6516,15 +6524,26 @@ void ironlake_enable_rc6(struct drm_device *dev)
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int ret;
 
+	/* rc6 disabled by default due to repeated reports of hanging during
+	 * boot and resume.
+	 */
+	if (!i915_enable_rc6)
+		return;
+
+	ret = ironlake_setup_rc6(dev);
+	if (ret)
+		return;
+
 	/*
 	 * GPU can automatically power down the render unit if given a page
 	 * to save state.
 	 */
 	ret = BEGIN_LP_RING(6);
 	if (ret) {
-		ironlake_disable_rc6(dev);
+		ironlake_teardown_rc6(dev);
 		return;
 	}
+
 	OUT_RING(MI_SUSPEND_FLUSH | MI_SUSPEND_FLUSH_EN);
 	OUT_RING(MI_SET_CONTEXT);
 	OUT_RING(dev_priv->renderctx->gtt_offset |
@@ -6541,6 +6560,7 @@ void ironlake_enable_rc6(struct drm_device *dev)
 	I915_WRITE(RSTDBYCTL, I915_READ(RSTDBYCTL) & ~RCX_SW_EXIT);
 }
 
+
 /* Set up chip specific display functions */
 static void intel_init_display(struct drm_device *dev)
 {
@@ -6783,21 +6803,9 @@ void intel_modeset_init(struct drm_device *dev)
 	if (IS_GEN6(dev))
 		gen6_enable_rps(dev_priv);
 
-	if (IS_IRONLAKE_M(dev)) {
-		dev_priv->renderctx = intel_alloc_context_page(dev);
-		if (!dev_priv->renderctx)
-			goto skip_rc6;
-		dev_priv->pwrctx = intel_alloc_context_page(dev);
-		if (!dev_priv->pwrctx) {
-			i915_gem_object_unpin(dev_priv->renderctx);
-			drm_gem_object_unreference(&dev_priv->renderctx->base);
-			dev_priv->renderctx = NULL;
-			goto skip_rc6;
-		}
+	if (IS_IRONLAKE_M(dev))
 		ironlake_enable_rc6(dev);
-	}
 
-skip_rc6:
 	INIT_WORK(&dev_priv->idle_work, intel_idle_update);
 	setup_timer(&dev_priv->idle_timer, intel_gpu_idle_timer,
 		    (unsigned long)dev);

drivers/gpu/drm/i915/intel_drv.h

@@ -298,7 +298,6 @@ extern void intel_crtc_fb_gamma_set(struct drm_crtc *crtc, u16 red, u16 green,
 extern void intel_crtc_fb_gamma_get(struct drm_crtc *crtc, u16 *red, u16 *green,
 				    u16 *blue, int regno);
 extern void intel_enable_clock_gating(struct drm_device *dev);
-extern void intel_disable_clock_gating(struct drm_device *dev);
 extern void ironlake_enable_drps(struct drm_device *dev);
 extern void ironlake_disable_drps(struct drm_device *dev);
 extern void gen6_enable_rps(struct drm_i915_private *dev_priv);