[PATCH net 1/2] mlxsw: core: Add validation of transceiver temperature thresholds

[Ido Schimmel]

From: Vadim Pasternak <vad...@nvidia.com>

Validate thresholds to avoid a single failure due to some transceiver
unreliability. Ignore the last readouts in case warning temperature is
above alarm temperature, since it can cause unexpected thermal
shutdown. Stay with the previous values and refresh threshold within
the next iteration.

This is a rare scenario, but it was observed at a customer site.

Fixes: 6a79507cfe94 ("mlxsw: core: Extend thermal module with per QSFP module 
thermal zones")
Signed-off-by: Vadim Pasternak <vad...@nvidia.com>
Reviewed-by: Jiri Pirko <j...@nvidia.com>
Signed-off-by: Ido Schimmel <ido...@nvidia.com>
---
 drivers/net/ethernet/mellanox/mlxsw/core_thermal.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/core_thermal.c 
b/drivers/net/ethernet/mellanox/mlxsw/core_thermal.c
index 8fa286ccdd6b..250a85049697 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/core_thermal.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/core_thermal.c
@@ -176,6 +176,12 @@ mlxsw_thermal_module_trips_update(struct device *dev, 
struct mlxsw_core *core,
        if (err)
                return err;
 
+       if (crit_temp > emerg_temp) {
+               dev_warn(dev, "%s : Critical threshold %d is above emergency 
threshold %d\n",
+                        tz->tzdev->type, crit_temp, emerg_temp);
+               return 0;
+       }
+
        /* According to the system thermal requirements, the thermal zones are
         * defined with four trip points. The critical and emergency
         * temperature thresholds, provided by QSFP module are set as "active"
@@ -190,11 +196,8 @@ mlxsw_thermal_module_trips_update(struct device *dev, 
struct mlxsw_core *core,
                tz->trips[MLXSW_THERMAL_TEMP_TRIP_NORM].temp = crit_temp;
        tz->trips[MLXSW_THERMAL_TEMP_TRIP_HIGH].temp = crit_temp;
        tz->trips[MLXSW_THERMAL_TEMP_TRIP_HOT].temp = emerg_temp;
-       if (emerg_temp > crit_temp)
-               tz->trips[MLXSW_THERMAL_TEMP_TRIP_CRIT].temp = emerg_temp +
+       tz->trips[MLXSW_THERMAL_TEMP_TRIP_CRIT].temp = emerg_temp +
                                        MLXSW_THERMAL_MODULE_TEMP_SHIFT;
-       else
-               tz->trips[MLXSW_THERMAL_TEMP_TRIP_CRIT].temp = emerg_temp;
 
        return 0;
 }
-- 
2.29.2