[Mellanox] Implement low power mode for cmis host management (#17159)

- Why I did it
For cmis host management mode, the prevous sysfs cannot be used for low power mode setting. This PR reuses existing low power mode implementation in sonic_xcvr package when CMIS host management mode is enabled

- How I did it
Use sonic_xcvr low power mode implementation when CMIS host management mode is enabled.

- How to verify it
Manual test for CMIS host management mode
Regression test for old mode and backward compatible test

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

@@ -397,6 +397,18 @@ class SFP(NvidiaSFPCommon):
         Returns:
             A Boolean, True if lpmode is enabled, False if disabled
         """
+        try:
+            if self.is_sw_control():
+                api = self.get_xcvr_api()
+                return api.get_lpmode() if api else False
+            elif DeviceDataManager.is_independent_mode():
+                file_path = SFP_SDK_MODULE_SYSFS_ROOT_TEMPLATE.format(self.sdk_index) + SFP_SYSFS_POWER_MODE
+                power_mode = utils.read_int_from_file(file_path)
+                return power_mode == POWER_MODE_LOW
+        except Exception as e:
+            print(e)
+            return False
+
         if utils.is_host():
             # To avoid performance issue,
             # call class level method to avoid initialize the whole sonic platform API
@@ -573,6 +585,24 @@ class SFP(NvidiaSFPCommon):
         Returns:
             A boolean, True if lpmode is set successfully, False if not
         """
+        try:
+            if self.is_sw_control():
+                api = self.get_xcvr_api()
+                if not api:
+                    return False
+                if api.get_lpmode() == lpmode:
+                    return True
+                api.set_lpmode(lpmode)
+                return api.get_lpmode() == lpmode
+            elif DeviceDataManager.is_independent_mode():
+                # FW control under CMIS host management mode. 
+                # Currently, we don't support set LPM under this mode.
+                # Just return False to indicate set Fail
+                return False
+        except Exception as e:
+            print(e)
+            return False
+
         if utils.is_host():
             # To avoid performance issue,
             # call class level method to avoid initialize the whole sonic platform API

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

@@ -312,6 +312,8 @@ class TestSfp:
         with pytest.raises(Exception):
             sfp.is_sw_control()
 
+    @mock.patch('sonic_platform.device_data.DeviceDataManager.is_independent_mode', mock.MagicMock(return_value=False))
+    @mock.patch('sonic_platform.sfp.SFP.is_sw_control', mock.MagicMock(return_value=False))
     @mock.patch('sonic_platform.utils.is_host', mock.MagicMock(side_effect = [True, True, False, False]))
     @mock.patch('subprocess.check_output', mock.MagicMock(side_effect = ['True', 'False']))
     @mock.patch('sonic_platform.sfp.SFP._get_lpmode', mock.MagicMock(side_effect = [True, False]))
@@ -323,6 +325,8 @@ class TestSfp:
         assert sfp.get_lpmode()
         assert not sfp.get_lpmode()
 
+    @mock.patch('sonic_platform.device_data.DeviceDataManager.is_independent_mode', mock.MagicMock(return_value=False))
+    @mock.patch('sonic_platform.sfp.SFP.is_sw_control', mock.MagicMock(return_value=False))
     @mock.patch('sonic_platform.utils.is_host', mock.MagicMock(side_effect = [True, True, False, False]))
     @mock.patch('subprocess.check_output', mock.MagicMock(side_effect = ['True', 'False']))
     @mock.patch('sonic_platform.sfp.SFP._set_lpmode', mock.MagicMock(side_effect = [True, False]))
@@ -333,3 +337,45 @@ class TestSfp:
         assert not sfp.set_lpmode(True)
         assert sfp.set_lpmode(False)
         assert not sfp.set_lpmode(False)
+        
+    @mock.patch('sonic_platform.device_data.DeviceDataManager.is_independent_mode', mock.MagicMock(return_value=True))
+    @mock.patch('sonic_platform.utils.read_int_from_file')
+    @mock.patch('sonic_platform.sfp.SFP.is_sw_control')
+    def test_get_lpmode_cmis_host_mangagement(self, mock_control, mock_read):
+        mock_control.return_value = True
+        sfp = SFP(0)
+        sfp.get_xcvr_api = mock.MagicMock(return_value=None)
+        assert not sfp.get_lpmode()
+        
+        mock_api = mock.MagicMock()
+        sfp.get_xcvr_api.return_value = mock_api
+        mock_api.get_lpmode = mock.MagicMock(return_value=False)
+        assert not sfp.get_lpmode()
+        
+        mock_api.get_lpmode.return_value = True
+        assert sfp.get_lpmode()
+        
+        mock_control.return_value = False
+        mock_read.return_value = 1
+        assert sfp.get_lpmode()
+        
+        mock_read.return_value = 2
+        assert not sfp.get_lpmode()
+
+    @mock.patch('sonic_platform.device_data.DeviceDataManager.is_independent_mode', mock.MagicMock(return_value=True))
+    @mock.patch('sonic_platform.sfp.SFP.is_sw_control')
+    def test_set_lpmode_cmis_host_mangagement(self, mock_control):
+        mock_control.return_value = True
+        sfp = SFP(0)
+        sfp.get_xcvr_api = mock.MagicMock(return_value=None)
+        assert not sfp.set_lpmode(False)
+        
+        mock_api = mock.MagicMock()
+        sfp.get_xcvr_api.return_value = mock_api
+        mock_api.get_lpmode = mock.MagicMock(return_value=False)
+        assert sfp.set_lpmode(False)
+        assert not sfp.set_lpmode(True)
+        
+        mock_control.return_value = False
+        assert not sfp.set_lpmode(True)
+        assert not sfp.set_lpmode(False)