only allow one active call in each platform. (#52823)

homeassistant/components/modbus/climate.py

@@ -194,13 +194,18 @@ class ModbusThermostat(BasePlatform, RestoreEntity, ClimateEntity):
         """Update Target & Current Temperature."""
         # remark "now" is a dummy parameter to avoid problems with
         # async_track_time_interval
+
+        # do not allow multiple active calls to the same platform
+        if self._call_active:
+            return
+        self._call_active = True
         self._target_temperature = await self._async_read_register(
             CALL_TYPE_REGISTER_HOLDING, self._target_temperature_register
         )
         self._current_temperature = await self._async_read_register(
             self._input_type, self._address
         )
-
+        self._call_active = False
         self.async_write_ha_state()
 
     async def _async_read_register(self, register_type, register) -> float | None: