mlxsw: core: Prevent duplication during QSFP module initialization

Verify during thermal initialization if QSFP module's entry is already
configured in order to prevent duplication.
Such scenario could happen in case two switch drivers (PCI and I2C
based) coexist and if after boot, splitting configuration is applied
for some ports and then I2C based driver is re-probed.
In such case after reboot same QSFP module, associated with split will
be discovered by I2C based driver few times, and it will cause a crash.

It could happen for example on system equipped with BMC (Baseboard
Management Controller), running I2C based driver, when the next steps
are performed:
- System boot
- Host side configures port spilt.
- BMC side is rebooted.

Fixes: 6a79507c ("mlxsw: core: Extend thermal module with per QSFP module thermal zones")
Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/core_thermal.c

@@ -111,7 +111,6 @@ struct mlxsw_thermal {
 	struct mlxsw_thermal_trip trips[MLXSW_THERMAL_NUM_TRIPS];
 	enum thermal_device_mode mode;
 	struct mlxsw_thermal_module *tz_module_arr;
-	unsigned int tz_module_num;
 };
 
 static inline u8 mlxsw_state_to_duty(int state)
@@ -711,6 +710,9 @@ mlxsw_thermal_module_init(struct device *dev, struct mlxsw_core *core,
 
 	module = mlxsw_reg_pmlp_module_get(pmlp_pl, 0);
 	module_tz = &thermal->tz_module_arr[module];
+	/* Skip if parent is already set (case of port split). */
+	if (module_tz->parent)
+		return 0;
 	module_tz->module = module;
 	module_tz->parent = thermal;
 	memcpy(module_tz->trips, default_thermal_trips,
@@ -718,13 +720,7 @@ mlxsw_thermal_module_init(struct device *dev, struct mlxsw_core *core,
 	/* Initialize all trip point. */
 	mlxsw_thermal_module_trips_reset(module_tz);
 	/* Update trip point according to the module data. */
-	err = mlxsw_thermal_module_trips_update(dev, core, module_tz);
-	if (err)
-		return err;
-
-	thermal->tz_module_num++;
-
-	return 0;
+	return mlxsw_thermal_module_trips_update(dev, core, module_tz);
 }
 
 static void mlxsw_thermal_module_fini(struct mlxsw_thermal_module *module_tz)
@@ -732,6 +728,7 @@ static void mlxsw_thermal_module_fini(struct mlxsw_thermal_module *module_tz)
 	if (module_tz && module_tz->tzdev) {
 		mlxsw_thermal_module_tz_fini(module_tz->tzdev);
 		module_tz->tzdev = NULL;
+		module_tz->parent = NULL;
 	}
 }
 
@@ -740,6 +737,7 @@ mlxsw_thermal_modules_init(struct device *dev, struct mlxsw_core *core,
 			   struct mlxsw_thermal *thermal)
 {
 	unsigned int module_count = mlxsw_core_max_ports(core);
+	struct mlxsw_thermal_module *module_tz;
 	int i, err;
 
 	thermal->tz_module_arr = kcalloc(module_count,
@@ -754,8 +752,11 @@ mlxsw_thermal_modules_init(struct device *dev, struct mlxsw_core *core,
 			goto err_unreg_tz_module_arr;
 	}
 
-	for (i = 0; i < thermal->tz_module_num; i++) {
-		err = mlxsw_thermal_module_tz_init(&thermal->tz_module_arr[i]);
+	for (i = 0; i < module_count - 1; i++) {
+		module_tz = &thermal->tz_module_arr[i];
+		if (!module_tz->parent)
+			continue;
+		err = mlxsw_thermal_module_tz_init(module_tz);
 		if (err)
 			goto err_unreg_tz_module_arr;
 	}