mlxsw: core_hwmon: Query MTMP before writing to set only relevant fields

The MTMP register controls various temperature settings on a per-sensor
basis. Subsequent patches are going to alter some of these settings for
sensors found on port modules in response to certain events.

In order to prevent the current callers that write to MTMP from
overriding these settings, have them first query the register and then
change only the relevant register fields.
Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -106,7 +106,7 @@ static ssize_t mlxsw_hwmon_temp_rst_store(struct device *dev,
 	struct mlxsw_hwmon_attr *mlwsw_hwmon_attr =
 			container_of(attr, struct mlxsw_hwmon_attr, dev_attr);
 	struct mlxsw_hwmon *mlxsw_hwmon = mlwsw_hwmon_attr->hwmon;
-	char mtmp_pl[MLXSW_REG_MTMP_LEN];
+	char mtmp_pl[MLXSW_REG_MTMP_LEN] = {0};
 	unsigned long val;
 	int index;
 	int err;
@@ -119,7 +119,13 @@ static ssize_t mlxsw_hwmon_temp_rst_store(struct device *dev,
 
 	index = mlxsw_hwmon_get_attr_index(mlwsw_hwmon_attr->type_index,
 					   mlxsw_hwmon->module_sensor_max);
-	mlxsw_reg_mtmp_pack(mtmp_pl, index, true, true);
+
+	mlxsw_reg_mtmp_sensor_index_set(mtmp_pl, index);
+	err = mlxsw_reg_query(mlxsw_hwmon->core, MLXSW_REG(mtmp), mtmp_pl);
+	if (err)
+		return err;
+	mlxsw_reg_mtmp_mte_set(mtmp_pl, true);
+	mlxsw_reg_mtmp_mtr_set(mtmp_pl, true);
 	err = mlxsw_reg_write(mlxsw_hwmon->core, MLXSW_REG(mtmp), mtmp_pl);
 	if (err) {
 		dev_err(mlxsw_hwmon->bus_info->dev, "Failed to reset temp sensor history\n");
@@ -570,7 +576,6 @@ static void mlxsw_hwmon_attr_add(struct mlxsw_hwmon *mlxsw_hwmon,
 static int mlxsw_hwmon_temp_init(struct mlxsw_hwmon *mlxsw_hwmon)
 {
 	char mtcap_pl[MLXSW_REG_MTCAP_LEN] = {0};
-	char mtmp_pl[MLXSW_REG_MTMP_LEN];
 	int i;
 	int err;
 
@@ -581,7 +586,15 @@ static int mlxsw_hwmon_temp_init(struct mlxsw_hwmon *mlxsw_hwmon)
 	}
 	mlxsw_hwmon->sensor_count = mlxsw_reg_mtcap_sensor_count_get(mtcap_pl);
 	for (i = 0; i < mlxsw_hwmon->sensor_count; i++) {
-		mlxsw_reg_mtmp_pack(mtmp_pl, i, true, true);
+		char mtmp_pl[MLXSW_REG_MTMP_LEN] = {0};
+
+		mlxsw_reg_mtmp_sensor_index_set(mtmp_pl, i);
+		err = mlxsw_reg_query(mlxsw_hwmon->core, MLXSW_REG(mtmp),
+				      mtmp_pl);
+		if (err)
+			return err;
+		mlxsw_reg_mtmp_mte_set(mtmp_pl, true);
+		mlxsw_reg_mtmp_mtr_set(mtmp_pl, true);
 		err = mlxsw_reg_write(mlxsw_hwmon->core,
 				      MLXSW_REG(mtmp), mtmp_pl);
 		if (err) {