drm/i915/guc: Allow preempt-client to be NULL

In the next patch, we may only conditionally allocate the preempt-client
if there is a global preempt context and so we need to be prepared in
case the preempt-client itself is NULL.

v2: Grep for more preempt_client.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Cc: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180207210544.26351-1-chris@chris-wilson.co.ukReviewed-by: Michel Thierry <michel.thierry@intel.com>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -2338,7 +2338,6 @@ static int i915_guc_info(struct seq_file *m, void *data)
 		return -ENODEV;
 
 	GEM_BUG_ON(!guc->execbuf_client);
-	GEM_BUG_ON(!guc->preempt_client);
 
 	seq_printf(m, "Doorbell map:\n");
 	seq_printf(m, "\t%*pb\n", GUC_NUM_DOORBELLS, guc->doorbell_bitmap);
@@ -2346,8 +2345,11 @@ static int i915_guc_info(struct seq_file *m, void *data)
 
 	seq_printf(m, "\nGuC execbuf client @ %p:\n", guc->execbuf_client);
 	i915_guc_client_info(m, dev_priv, guc->execbuf_client);
-	seq_printf(m, "\nGuC preempt client @ %p:\n", guc->preempt_client);
+	if (guc->preempt_client) {
+		seq_printf(m, "\nGuC preempt client @ %p:\n",
+			   guc->preempt_client);
 		i915_guc_client_info(m, dev_priv, guc->preempt_client);
+	}
 
 	i915_guc_log_info(m, dev_priv);
 

drivers/gpu/drm/i915/intel_guc_submission.c

@@ -832,11 +832,13 @@ static int guc_clients_doorbell_init(struct intel_guc *guc)
 	if (ret)
 		return ret;
 
+	if (guc->preempt_client) {
 		ret = create_doorbell(guc->preempt_client);
 		if (ret) {
 			destroy_doorbell(guc->execbuf_client);
 			return ret;
 		}
+	}
 
 	return 0;
 }
@@ -848,8 +850,11 @@ static void guc_clients_doorbell_fini(struct intel_guc *guc)
 	 * Instead of trying (in vain) to communicate with it, let's just
 	 * cleanup the doorbell HW and our internal state.
 	 */
+	if (guc->preempt_client) {
 		__destroy_doorbell(guc->preempt_client);
-	__update_doorbell_desc(guc->preempt_client, GUC_DOORBELL_INVALID);
+		__update_doorbell_desc(guc->preempt_client,
+				       GUC_DOORBELL_INVALID);
+	}
 	__destroy_doorbell(guc->execbuf_client);
 	__update_doorbell_desc(guc->execbuf_client, GUC_DOORBELL_INVALID);
 }
@@ -998,10 +1003,11 @@ static void guc_clients_destroy(struct intel_guc *guc)
 {
 	struct intel_guc_client *client;
 
-	client = fetch_and_zero(&guc->execbuf_client);
+	client = fetch_and_zero(&guc->preempt_client);
+	if (client)
 		guc_client_free(client);
 
-	client = fetch_and_zero(&guc->preempt_client);
+	client = fetch_and_zero(&guc->execbuf_client);
 	guc_client_free(client);
 }
 
@@ -1160,6 +1166,7 @@ int intel_guc_submission_enable(struct intel_guc *guc)
 	GEM_BUG_ON(!guc->execbuf_client);
 
 	guc_reset_wq(guc->execbuf_client);
+	if (guc->preempt_client)
 		guc_reset_wq(guc->preempt_client);
 
 	err = intel_guc_sample_forcewake(guc);

drivers/gpu/drm/i915/selftests/intel_guc.c

@@ -87,7 +87,7 @@ static int validate_client(struct intel_guc_client *client,
 
 static bool client_doorbell_in_sync(struct intel_guc_client *client)
 {
-	return doorbell_ok(client->guc, client->doorbell_id);
+	return !client || doorbell_ok(client->guc, client->doorbell_id);
 }
 
 /*
@@ -137,7 +137,6 @@ static int igt_guc_clients(void *args)
 		goto unlock;
 	}
 	GEM_BUG_ON(!guc->execbuf_client);
-	GEM_BUG_ON(!guc->preempt_client);
 
 	err = validate_client(guc->execbuf_client,
 			      GUC_CLIENT_PRIORITY_KMD_NORMAL, false);
@@ -146,16 +145,18 @@ static int igt_guc_clients(void *args)
 		goto out;
 	}
 
+	if (guc->preempt_client) {
 		err = validate_client(guc->preempt_client,
 				      GUC_CLIENT_PRIORITY_KMD_HIGH, true);
 		if (err) {
 			pr_err("preempt client validation failed\n");
 			goto out;
 		}
+	}
 
 	/* each client should now have reserved a doorbell */
 	if (!has_doorbell(guc->execbuf_client) ||
-	    !has_doorbell(guc->preempt_client)) {
+	    (guc->preempt_client && !has_doorbell(guc->preempt_client))) {
 		pr_err("guc_clients_create didn't reserve doorbells\n");
 		err = -EINVAL;
 		goto out;
@@ -224,6 +225,7 @@ static int igt_guc_clients(void *args)
 	 * clients during unload.
 	 */
 	destroy_doorbell(guc->execbuf_client);
+	if (guc->preempt_client)
 		destroy_doorbell(guc->preempt_client);
 	guc_clients_destroy(guc);
 	guc_clients_create(guc);