drm/i915/guc: fix GuC suspend/resume

The ENTER/EXIT_S_STATE actions queue the save/restore operation in GuC
FW and then return, so waiting on the H2G is not enough to guarantee
GuC is done.
When all the processing is done, GuC writes 0 to scratch register 14,
so we can poll on that. Note that GuC does not ensure that the value
in the register is different from 0 while the action is in progress
so we need to take care of that ourselves as well.

v2: improve comment, return early on GuC error and improve error
    message (Michal)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20181016224648.2326-1-daniele.ceraolospurio@intel.com

drivers/gpu/drm/i915/intel_guc.c

@@ -521,6 +521,44 @@ int intel_guc_auth_huc(struct intel_guc *guc, u32 rsa_offset)
 	return intel_guc_send(guc, action, ARRAY_SIZE(action));
 }
 
+/*
+ * The ENTER/EXIT_S_STATE actions queue the save/restore operation in GuC FW and
+ * then return, so waiting on the H2G is not enough to guarantee GuC is done.
+ * When all the processing is done, GuC writes INTEL_GUC_SLEEP_STATE_SUCCESS to
+ * scratch register 14, so we can poll on that. Note that GuC does not ensure
+ * that the value in the register is different from
+ * INTEL_GUC_SLEEP_STATE_SUCCESS while the action is in progress so we need to
+ * take care of that ourselves as well.
+ */
+static int guc_sleep_state_action(struct intel_guc *guc,
+				  const u32 *action, u32 len)
+{
+	struct drm_i915_private *dev_priv = guc_to_i915(guc);
+	int ret;
+	u32 status;
+
+	I915_WRITE(SOFT_SCRATCH(14), INTEL_GUC_SLEEP_STATE_INVALID_MASK);
+
+	ret = intel_guc_send(guc, action, len);
+	if (ret)
+		return ret;
+
+	ret = __intel_wait_for_register(dev_priv, SOFT_SCRATCH(14),
+					INTEL_GUC_SLEEP_STATE_INVALID_MASK,
+					0, 0, 10, &status);
+	if (ret)
+		return ret;
+
+	if (status != INTEL_GUC_SLEEP_STATE_SUCCESS) {
+		DRM_ERROR("GuC failed to change sleep state. "
+			  "action=0x%x, err=%u\n",
+			  action[0], status);
+		return -EIO;
+	}
+
+	return 0;
+}
+
 /**
  * intel_guc_suspend() - notify GuC entering suspend state
  * @guc:	the guc
@@ -533,7 +571,7 @@ int intel_guc_suspend(struct intel_guc *guc)
 		intel_guc_ggtt_offset(guc, guc->shared_data)
 	};
 
-	return intel_guc_send(guc, data, ARRAY_SIZE(data));
+	return guc_sleep_state_action(guc, data, ARRAY_SIZE(data));
 }
 
 /**
@@ -571,7 +609,7 @@ int intel_guc_resume(struct intel_guc *guc)
 		intel_guc_ggtt_offset(guc, guc->shared_data)
 	};
 
-	return intel_guc_send(guc, data, ARRAY_SIZE(data));
+	return guc_sleep_state_action(guc, data, ARRAY_SIZE(data));
 }
 
 /**

drivers/gpu/drm/i915/intel_guc_fwif.h

@@ -687,6 +687,13 @@ enum intel_guc_report_status {
 	INTEL_GUC_REPORT_STATUS_COMPLETE = 0x4,
 };
 
+enum intel_guc_sleep_state_status {
+	INTEL_GUC_SLEEP_STATE_SUCCESS = 0x0,
+	INTEL_GUC_SLEEP_STATE_PREEMPT_TO_IDLE_FAILED = 0x1,
+	INTEL_GUC_SLEEP_STATE_ENGINE_RESET_FAILED = 0x2
+#define INTEL_GUC_SLEEP_STATE_INVALID_MASK 0x80000000
+};
+
 #define GUC_LOG_CONTROL_LOGGING_ENABLED	(1 << 0)
 #define GUC_LOG_CONTROL_VERBOSITY_SHIFT	4
 #define GUC_LOG_CONTROL_VERBOSITY_MASK	(0xF << GUC_LOG_CONTROL_VERBOSITY_SHIFT)