add risc-v board Sipeed Longan Nano support

board/SipeedLonganNano/eclipse/hello_world/main.c

@@ -0,0 +1,83 @@
+#include "mcu_init.h"
+#include "tos.h"
+
+#define TASK_SIZE 1024
+k_task_t k_task_task1;
+k_task_t k_task_task2;
+uint8_t k_task1_stk[TASK_SIZE];
+uint8_t k_task2_stk[TASK_SIZE];
+
+int share = 0xCBA7F9;
+k_sem_t sem;
+
+typedef struct {
+    int port;
+    int pin;
+} Led_t;
+
+Led_t leds[] = {
+        { LEDR_GPIO_PORT, LEDR_PIN },
+        { LEDG_GPIO_PORT, LEDG_PIN },
+        { LEDB_GPIO_PORT, LEDB_PIN }
+};
+
+void task1(void *pdata)
+{
+    int task_cnt1 = 0;
+    while (1) {
+        printf("hello world from %s cnt: %d\n", __func__, task_cnt1++);
+        tos_sem_pend(&sem, ~0U);
+
+        for(int i=0; i<sizeof(leds)/sizeof(Led_t); i++) {
+            int on = !(task_cnt1 & (1 << i));
+            gpio_bit_write(leds[i].port, leds[i].pin, on);
+        }
+    }
+}
+
+void task2(void *pdata)
+{
+    int task_cnt2 = 0;
+    while (1) {
+        share++;
+        for(int i=0; i<5; i++) {
+            printf("hello world from %s cnt: %08x\n", __func__, task_cnt2--);
+            tos_task_delay(200);
+        }
+        tos_sem_post(&sem);
+    }
+}
+
+
+void main(void) {
+    board_init();
+
+    usart0_init(115200);
+
+    tos_knl_init();
+
+    tos_task_create(&k_task_task1, "task1", task1, NULL, 3, k_task1_stk, TASK_SIZE, 0);
+    tos_task_create(&k_task_task2, "task2", task2, NULL, 3, k_task2_stk, TASK_SIZE, 0);
+
+    k_err_t err = tos_sem_create(&sem, 1);
+    if (err != K_ERR_NONE) {
+        goto die;
+    }
+
+    tos_knl_start();
+
+die:
+    while (1) {
+        asm("wfi;");
+    }
+}
+
+
+int _put_char(int ch)
+{
+    usart_data_transmit(USART0, (uint8_t) ch );
+    while (usart_flag_get(USART0, USART_FLAG_TBE)== RESET){
+    }
+
+    return ch;
+}