[Mellanox] Adjust PSU voltage WA (#10619)

- Why I did it
InvalidPsuVolWA.run might raise exception if user power off PSU when it is running. This exception is not caught and will be raised to psud which causes psud failed to update PSU data to DB.

- How I did it
1. Change the log level when WA does not work. This could happen when user power off PSU, hence changing the log level from error to warning is better
2. Change the wait time from 5 to 1 to avoid introduce too much delay in psud. 1 second is usually enough per my test
3. Give a default return value for function get_voltage_low_threshold and get_voltage_high_threshold to avoid exception reach to psud

- How to verify it
Manual test.
Run sonic-mgmt regression

platform/mellanox/mlnx-platform-api/sonic_platform/psu.py

@@ -397,6 +397,7 @@ class Psu(FixedPsu):
 
         return None
 
+    @utils.default_return(None)
     def get_voltage_high_threshold(self):
         """
         Retrieves the high threshold PSU voltage output
@@ -414,10 +415,12 @@ class Psu(FixedPsu):
             if 'max' in capability:
                 max_voltage = utils.read_int_from_file(self.psu_voltage_max, log_func=logger.log_info)
                 max_voltage = InvalidPsuVolWA.run(self, max_voltage, self.psu_voltage_max)
-                return float(max_voltage) / 1000
+                if max_voltage:
+                    return float(max_voltage) / 1000
 
         return None
 
+    @utils.default_return(None)
     def get_voltage_low_threshold(self):
         """
         Retrieves the low threshold PSU voltage output
@@ -435,7 +438,8 @@ class Psu(FixedPsu):
             if 'min' in capability:
                 min_voltage = utils.read_int_from_file(self.psu_voltage_min, log_func=logger.log_info)
                 min_voltage = InvalidPsuVolWA.run(self, min_voltage, self.psu_voltage_min)
-                return float(min_voltage) / 1000
+                if min_voltage:
+                    return float(min_voltage) / 1000
 
         return None
 
@@ -471,7 +475,7 @@ class InvalidPsuVolWA:
     EXPECT_PLATFORMS = ['x86_64-mlnx_msn3700-r0', 'x86_64-mlnx_msn3700c-r0', 'x86_64-mlnx_msn3800-r0', 'x86_64-mlnx_msn4600c-r0']
     MFR_FIELD = 'MFR_NAME'
     CAPACITY_FIELD = 'CAPACITY'
-    WAIT_TIME = 5
+    WAIT_TIME = 1
 
     @classmethod
     def run(cls, psu, threshold_value, threshold_file):
@@ -499,8 +503,8 @@ class InvalidPsuVolWA:
             logger.log_warning('PSU {} threshold file {} value {}, but its capacity is {}'.format(psu.index, threshold_file, threshold_value, capacity))
             return threshold_value
 
-        # Run a sensor -s command to triger hardware to get the real threashold value
-        utils.run_command('sensor -s')
+        # Run a sensors -s command to triger hardware to get the real threashold value
+        utils.run_command('sensors -s')
 
         # Wait for the threshold value change
         return cls.wait_set_done(threshold_file)
@@ -516,5 +520,7 @@ class InvalidPsuVolWA:
             wait_time -= 1
             time.sleep(1)
 
-        logger.log_error('sensor -s does not recover PSU threshold sensor after {} seconds'.format(cls.WAIT_TIME))
+        # It is enough to use warning here because user might power off/on the PSU which may cause threshold_file
+        # does not exist
+        logger.log_warning('sensors -s does not recover PSU threshold sensor after {} seconds'.format(cls.WAIT_TIME))
         return None

platform/mellanox/mlnx-platform-api/tests/test_psu.py

@@ -152,4 +152,4 @@ class TestPsu:
         # Normal
         vpd_info[InvalidPsuVolWA.CAPACITY_FIELD] = InvalidPsuVolWA.EXPECT_CAPACITY
         assert InvalidPsuVolWA.run(psu, InvalidPsuVolWA.INVALID_VOLTAGE_VALUE, '') == 9999
-        mock_run_command.assert_called_with('sensor -s')
+        mock_run_command.assert_called_with('sensors -s')