freemodbus: add affinity option for modbus stack tasks

components/freemodbus/Kconfig

@@ -33,6 +33,29 @@ menu "Modbus configuration"
             Modbus UART driver event task priority.
             The priority of Modbus controller task is equal to (CONFIG_MB_SERIAL_TASK_PRIO - 1).
 
+    choice MB_PORT_TASK_AFFINITY
+        prompt "Modbus task affinity"
+        default MB_PORT_TASK_AFFINITY_CPU0
+        depends on !FREERTOS_UNICORE
+        help
+            Allows setting the core affinity of the Modbus controller task, i.e. whether the task is pinned to
+            particular CPU, or allowed to run on any CPU.
+
+        config MB_PORT_TASK_AFFINITY_NO_AFFINITY
+            bool "No affinity"
+        config MB_PORT_TASK_AFFINITY_CPU0
+            bool "CPU0"
+        config MB_PORT_TASK_AFFINITY_CPU1
+            bool "CPU1"
+
+    endchoice
+
+    config MB_PORT_TASK_AFFINITY
+        hex
+        default FREERTOS_NO_AFFINITY if MB_PORT_TASK_AFFINITY_NO_AFFINITY || FREERTOS_UNICORE
+        default 0x0 if MB_PORT_TASK_AFFINITY_CPU0
+        default 0x1 if MB_PORT_TASK_AFFINITY_CPU1
+
     config MB_CONTROLLER_SLAVE_ID_SUPPORT
         bool "Modbus controller slave ID support"
         default n

components/freemodbus/port/port.h

@@ -66,6 +66,9 @@
 #define EXIT_CRITICAL_SECTION( )  { vMBPortExitCritical(); \
                                     ESP_LOGD(MB_PORT_TAG,"%s: Port exit critical", __func__); }
 
+// The task affinity for Modbus stack tasks
+#define MB_PORT_TASK_AFFINITY           (CONFIG_MB_PORT_TASK_AFFINITY)
+
 typedef char    BOOL;
 
 typedef unsigned char UCHAR;

components/freemodbus/port/portserial.c

@@ -241,8 +241,10 @@ BOOL xMBPortSerialInit(UCHAR ucPORT, ULONG ulBaudRate,
             "mb serial set rx timeout failure, uart_set_rx_timeout() returned (0x%x).", (uint32_t)xErr);
 #endif
     // Create a task to handle UART events
-    BaseType_t xStatus = xTaskCreate(vUartTask, "uart_queue_task", MB_SERIAL_TASK_STACK_SIZE,
-                                        NULL, MB_SERIAL_TASK_PRIO, &xMbTaskHandle);
+    BaseType_t xStatus = xTaskCreatePinnedToCore(vUartTask, "uart_queue_task",
+                                                    MB_SERIAL_TASK_STACK_SIZE,
+                                                    NULL, MB_SERIAL_TASK_PRIO,
+                                                    &xMbTaskHandle, MB_PORT_TASK_AFFINITY);
     if (xStatus != pdPASS) {
         vTaskDelete(xMbTaskHandle);
         // Force exit from function with failure