drm/i915: clear error registers after error capture

We need to clear the register in order to get correct value after the
next potential hang.

v2: Centralize error register clearing in i915_irq.c (Chris)

v3: Don't read gen8 register on < gen6 (Chris)

v4: Don't swap gen8+ & gen6+ code... (Chris)
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180830132424.21940-1-lionel.g.landwerlin@intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -2807,6 +2807,8 @@ extern void intel_irq_fini(struct drm_i915_private *dev_priv);
 int intel_irq_install(struct drm_i915_private *dev_priv);
 void intel_irq_uninstall(struct drm_i915_private *dev_priv);
 
+void i915_clear_error_registers(struct drm_i915_private *dev_priv);
+
 static inline bool intel_gvt_active(struct drm_i915_private *dev_priv)
 {
 	return dev_priv->gvt;

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -2337,7 +2337,7 @@ static bool needs_idle_maps(struct drm_i915_private *dev_priv)
 	return IS_GEN5(dev_priv) && IS_MOBILE(dev_priv) && intel_vtd_active();
 }
 
-static void gen6_check_and_clear_faults(struct drm_i915_private *dev_priv)
+static void gen6_check_faults(struct drm_i915_private *dev_priv)
 {
 	struct intel_engine_cs *engine;
 	enum intel_engine_id id;
@@ -2355,15 +2355,11 @@ static void gen6_check_and_clear_faults(struct drm_i915_private *dev_priv)
 					 fault & RING_FAULT_GTTSEL_MASK ? "GGTT" : "PPGTT",
 					 RING_FAULT_SRCID(fault),
 					 RING_FAULT_FAULT_TYPE(fault));
-			I915_WRITE(RING_FAULT_REG(engine),
-				   fault & ~RING_FAULT_VALID);
 		}
 	}
-
-	POSTING_READ(RING_FAULT_REG(dev_priv->engine[RCS]));
 }
 
-static void gen8_check_and_clear_faults(struct drm_i915_private *dev_priv)
+static void gen8_check_faults(struct drm_i915_private *dev_priv)
 {
 	u32 fault = I915_READ(GEN8_RING_FAULT_REG);
 
@@ -2388,22 +2384,20 @@ static void gen8_check_and_clear_faults(struct drm_i915_private *dev_priv)
 				 GEN8_RING_FAULT_ENGINE_ID(fault),
 				 RING_FAULT_SRCID(fault),
 				 RING_FAULT_FAULT_TYPE(fault));
-		I915_WRITE(GEN8_RING_FAULT_REG,
-			   fault & ~RING_FAULT_VALID);
 	}
-
-	POSTING_READ(GEN8_RING_FAULT_REG);
 }
 
 void i915_check_and_clear_faults(struct drm_i915_private *dev_priv)
 {
 	/* From GEN8 onwards we only have one 'All Engine Fault Register' */
 	if (INTEL_GEN(dev_priv) >= 8)
-		gen8_check_and_clear_faults(dev_priv);
+		gen8_check_faults(dev_priv);
 	else if (INTEL_GEN(dev_priv) >= 6)
-		gen6_check_and_clear_faults(dev_priv);
+		gen6_check_faults(dev_priv);
 	else
 		return;
+
+	i915_clear_error_registers(dev_priv);
 }
 
 void i915_gem_suspend_gtt_mappings(struct drm_i915_private *dev_priv)

drivers/gpu/drm/i915/i915_irq.c

@@ -3215,7 +3215,7 @@ static void i915_reset_device(struct drm_i915_private *dev_priv,
 		kobject_uevent_env(kobj, KOBJ_CHANGE, reset_done_event);
 }
 
-static void i915_clear_error_registers(struct drm_i915_private *dev_priv)
+void i915_clear_error_registers(struct drm_i915_private *dev_priv)
 {
 	u32 eir;
 
@@ -3238,6 +3238,22 @@ static void i915_clear_error_registers(struct drm_i915_private *dev_priv)
 		I915_WRITE(EMR, I915_READ(EMR) | eir);
 		I915_WRITE(IIR, I915_MASTER_ERROR_INTERRUPT);
 	}
+
+	if (INTEL_GEN(dev_priv) >= 8) {
+		I915_WRITE(GEN8_RING_FAULT_REG,
+			   I915_READ(GEN8_RING_FAULT_REG) & ~RING_FAULT_VALID);
+		POSTING_READ(GEN8_RING_FAULT_REG);
+	} else if (INTEL_GEN(dev_priv) >= 6) {
+		struct intel_engine_cs *engine;
+		enum intel_engine_id id;
+
+		for_each_engine(engine, dev_priv, id) {
+			I915_WRITE(RING_FAULT_REG(engine),
+				   I915_READ(RING_FAULT_REG(engine)) &
+				   ~RING_FAULT_VALID);
+		}
+		POSTING_READ(RING_FAULT_REG(dev_priv->engine[RCS]));
+	}
 }
 
 /**