mlxsw: core: Add support for negative temperature readout

Extend macros MLXSW_REG_MTMP_TEMP_TO_MC() to allow support of negative
temperature readout, since chip and others thermal components are
capable of operating within the negative temperature.
With no such support negative temperature will be consider as very high
temperature and it will cause wrong readout and thermal shutdown.
For negative values 2`s complement is used.
Tested in chamber.
Example of chip ambient temperature readout with chamber temperature:
-10 Celsius:
temp1:             -6.0C  (highest =  -5.0C)
-5 Celsius:
temp1:             -1.0C  (highest =  -1.0C)

v2 (Andrew Lunn):
* Replace '%u' with '%d' in mlxsw_hwmon_module_temp_show()

Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 5 deletions

diff --git a/drivers/net/ethernet/mellanox/mlxsw/reg.h b/drivers/net/ethernet/mellanox/mlxsw/reg.h
index 452f645fa040..e5f6bfd8a35a 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/reg.h
+++ b/drivers/net/ethernet/mellanox/mlxsw/reg.h
@@ -8050,7 +8050,10 @@ MLXSW_REG_DEFINE(mtmp, MLXSW_REG_MTMP_ID, MLXSW_REG_MTMP_LEN);
 MLXSW_ITEM32(reg, mtmp, sensor_index, 0x00, 0, 12);
 
 /* Convert to milli degrees Celsius */
-#define MLXSW_REG_MTMP_TEMP_TO_MC(val) (val * 125)
+#define MLXSW_REG_MTMP_TEMP_TO_MC(val) ({ typeof(val) v_ = (val); \
+					  ((v_) >= 0) ? ((v_) * 125) : \
+					  ((s16)((GENMASK(15, 0) + (v_) + 1) \
+					   * 125)); })
 
 /* reg_mtmp_temperature
  * Temperature reading from the sensor. Reading is in 0.125 Celsius
@@ -8121,11 +8124,10 @@ static inline void mlxsw_reg_mtmp_pack(char *payload, u16 sensor_index,
 						    MLXSW_REG_MTMP_THRESH_HI);
 }
 
-static inline void mlxsw_reg_mtmp_unpack(char *payload, unsigned int *p_temp,
-					 unsigned int *p_max_temp,
-					 char *sensor_name)
+static inline void mlxsw_reg_mtmp_unpack(char *payload, int *p_temp,
+					 int *p_max_temp, char *sensor_name)
 {
-	u16 temp;
+	s16 temp;
 
 	if (p_temp) {
 		temp = mlxsw_reg_mtmp_temperature_get(payload);