firmware: arm_ffa: Unregister bus notifier on teardown for FF-A v1.0

For FF-A v1.0 the driver registers a bus notifier to backfill UUID
matching, but the notifier was never unregistered on cleanup paths.
Track the registration state and unregister it during teardown and early
partition-setup failure.

Fixes: 9dd1593 ("firmware: arm_ffa: Move the FF-A v1.0 NULL UUID workaround to bus notifier")
Link: https://patch.msgid.link/20260428-ffa_fixes-v2-5-8595ae450034@kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>

Author: Sudeep Holla

drivers/firmware/arm_ffa/driver.c

@@ -101,6 +101,7 @@ struct ffa_drv_info {
 	bool mem_ops_native;
 	bool msg_direct_req2_supp;
 	bool bitmap_created;
+	bool bus_notifier_registered;
 	bool notif_enabled;
 	unsigned int sched_recv_irq;
 	unsigned int notif_pend_irq;
@@ -1630,6 +1631,15 @@ static struct notifier_block ffa_bus_nb = {
 	.notifier_call = ffa_bus_notifier,
 };
 
+static void ffa_bus_notifier_unregister(void)
+{
+	if (!drv_info->bus_notifier_registered)
+		return;
+
+	bus_unregister_notifier(&ffa_bus_type, &ffa_bus_nb);
+	drv_info->bus_notifier_registered = false;
+}
+
 static int ffa_xa_add_partition_info(struct ffa_device *dev)
 {
 	struct ffa_dev_part_info *info;
@@ -1713,6 +1723,8 @@ static void ffa_partitions_cleanup(void)
 	struct list_head *phead;
 	unsigned long idx;
 
+	ffa_bus_notifier_unregister();
+
 	/* Clean up/free all registered devices */
 	ffa_devices_unregister();
 
@@ -1740,11 +1752,14 @@ static int ffa_setup_partitions(void)
 		ret = bus_register_notifier(&ffa_bus_type, &ffa_bus_nb);
 		if (ret)
 			pr_err("Failed to register FF-A bus notifiers\n");
+		else
+			drv_info->bus_notifier_registered = true;
 	}
 
 	count = ffa_partition_probe(&uuid_null, &pbuf);
 	if (count <= 0) {
 		pr_info("%s: No partitions found, error %d\n", __func__, count);
+		ffa_bus_notifier_unregister();
 		return -EINVAL;
 	}