i3c: master: Serialize i3c_set_hotjoin() with the maintenance lock

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.

Fixes: 317bacf960a48 ("i3c: master: add enable(disable) hot join in sys entry")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260608054312.10604-3-adrian.hunter@intel.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
index 5b64e40dae67f0090eb53c610f0430f541156222..a3a790a142863799bf08480e0fd9bdb36a8f3bf1 100644 (file)
--- 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);