[PATCH 2/8] i3c: master: Serialize i3c_set_hotjoin() with the maintenance lock

[Adrian Hunter <adrian.hunter@intel.com>]

i3c_set_hotjoin() dispatches the controller's enable_hotjoin() or
disable_hotjoin() op and updates master->hotjoin under
i3c_bus_normaluse_lock(). That lock is a read-side acquisition of
bus->lock (down_read()), so it does not exclude concurrent callers.

The hotjoin sysfs attribute can be opened multiple times, and writes
through different opens are not serialized.  Two concurrent writers
to "hotjoin" can therefore race in i3c_set_hotjoin(), with the
controller op and the master->hotjoin store from one call interleaving
with the other.  The hardware enable/disable state and the value reported
by hotjoin_show() can end up out of sync.

Take i3c_bus_maintenance_lock() instead. Toggling Hot Join enable
changes bus state and is conceptually a maintenance operation, so the
write-side acquisition of bus->lock is the appropriate lock and
serializes concurrent callers against each other and against other
maintenance operations.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
 drivers/i3c/master.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
index ab11e2d79aab..38ffc8713167 100644
--- a/drivers/i3c/master.c
+++ b/drivers/i3c/master.c
@@ -649,7 +649,7 @@ static int i3c_set_hotjoin(struct i3c_master_controller *master, bool enable)
 			return ret;
 	}
 
-	i3c_bus_normaluse_lock(&master->bus);
+	i3c_bus_maintenance_lock(&master->bus);
 
 	if (enable)
 		ret = master->ops->enable_hotjoin(master);
@@ -659,7 +659,7 @@ static int i3c_set_hotjoin(struct i3c_master_controller *master, bool enable)
 	if (!ret)
 		master->hotjoin = enable;
 
-	i3c_bus_normaluse_unlock(&master->bus);
+	i3c_bus_maintenance_unlock(&master->bus);
 
 	if ((enable && ret) || (!enable && !ret) || master->rpm_ibi_allowed)
 		i3c_master_rpm_put(master);
-- 
2.51.0