K210 FreeRTOS SDK启动分析

本文主要是介绍K210 FreeRTOS SDK启动分析，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

一、目的

最近在开始使用K210 FreeRTOS SDK进行应用开发，但是在使用过程发现程序的行为和预期不一致，怀疑这个官方提供的FreeRTOS SDK适配的不是很完整，故本着学习的目的跟着代码分析一下启动过程。

二、必备知识

对freertos有一些基本了解，了解滴答时钟（tick）、任务、任务优先级、空闲任务等基本概念；知道如何配置freertos一些选项，通过修改FreeRTOSConfig.h进行配置。

diff --git a/lib/freertos/conf/FreeRTOSConfig.h b/lib/freertos/conf/FreeRTOSConfig.h
index dac0af6..14fd619 100755
--- a/lib/freertos/conf/FreeRTOSConfig.h
+++ b/lib/freertos/conf/FreeRTOSConfig.h
@@ -59,14 +59,14 @@/* clock */#define configCPU_CLOCK_HZ                                     uxPortGetCPUClock()#define configTICK_CLOCK_HZ                                    ( configCPU_CLOCK_HZ / 50 )
-#define configTICK_RATE_HZ                                     ( ( TickType_t ) 100 )
+#define configTICK_RATE_HZ                                     ( ( TickType_t ) 1000 )/* multithreading */#define configUSE_NEWLIB_REENTRANT                             1#define configUSE_PREEMPTION                                   1#define configUSE_PORT_OPTIMISED_TASK_SELECTION        0
-#define configMAX_PRIORITIES                                   ( 5 )
+#define configMAX_PRIORITIES                                   ( 16 )#define configMAX_TASK_NAME_LEN                                        ( 16 )#define configUSE_TRACE_FACILITY                               1#define configUSE_16_BIT_TICKS                                 0
@@ -108,9 +108,9 @@ enum#define configMAX_CO_ROUTINE_PRIORITIES                        ( 2 )/* Software timer definitions. */
-#define configUSE_TIMERS                                               0
-#define configTIMER_TASK_PRIORITY                              ( 0 )
-#define configTIMER_QUEUE_LENGTH                               2
+#define configUSE_TIMERS                                               1
+#define configTIMER_TASK_PRIORITY                              ( configMAX_PRIORITIES - 1 )
+#define configTIMER_QUEUE_LENGTH                               8#define configTIMER_TASK_STACK_DEPTH                   ( configMINIMAL_STACK_SIZE )

　其中configTICK_RATE_HZ设置tick频率，此处修改为1000Hz，即1ms；configMAX_PRIORITIES设置系统支持的最多优先级，值越大，优先级越高，创建任务时可以配置的最大优先级为configMAX_PRIORITIES -1；configUSE_TIMERS配置系统软件定时器，即rtos实现的软件定时器，一般情况下其优先级需要设置为最大，即configMAX_PRIORITIES -1；

三、启动分析

根据教程，我们是从src/hello_world/main.c程序开始熟悉sdk的调用。

#include <stdio.h>                                                              int main() {                                                                    printf("Hello K210!!!\n");                                                  while (1);                                                                  
}   

此处有个疑问，谁调用了main？rtos是否已经启动了？

针对以上疑问，我们做了这样一个尝试。

#include <stdio.h>
#include "FreeRTOS.h"
#include "task.h"static void task_0(void *args) {while (1) {printf("task 0 is polling\n");vTaskDelay(1000 / portTICK_PERIOD_MS);}vTaskDelete(NULL);
}static void task_1(void *args) {while (1) {printf("task 1 is polling\n");vTaskDelay(1000 / portTICK_PERIOD_MS);}vTaskDelete(NULL);
}int main() {printf("Hello K210!!!\n");xTaskCreateAtProcessor(0, task_0, "task0", 1024, NULL, 5, NULL);xTaskCreateAtProcessor(0, task_1, "task1", 1024, NULL, 5, NULL);while (1) {printf("main is polling\n");vTaskDelay(2000 / portTICK_PERIOD_MS);}
}

我们在core 0上面创建了两个任务，并且在mian函数里面也有循环打印。通过编译烧写验证后，确认rtos已经正常工作。

我们知道freertos是通过vTaskStartScheduler接口调用开启多任务调度的，我们跟踪源码lib/freertos/os_entry.c

/* Copyright 2018 Canaan Inc.** Licensed under the Apache License, Version 2.0 (the "License");* you may not use this file except in compliance with the License.* You may obtain a copy of the License at**     http://www.apache.org/licenses/LICENSE-2.0** Unless required by applicable law or agreed to in writing, software* distributed under the License is distributed on an "AS IS" BASIS,* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.* See the License for the specific language governing permissions and* limitations under the License.*/
#include "FreeRTOS.h"
#include "core_sync.h"
#include "kernel/device_priv.h"
#include "task.h"
#include <clint.h>
#include <encoding.h>
#include <fpioa.h>
#include <stdio.h>
#include <stdlib.h>typedef struct
{int (*user_main)(int, char **);int ret;
} main_thunk_param_t;extern void __libc_init_array(void);
extern void __libc_fini_array(void);static StaticTask_t s_idle_task[portNUM_PROCESSORS];
static StackType_t s_idle_task_stack[portNUM_PROCESSORS][configMINIMAL_STACK_SIZE];
static StaticTask_t s_timer_task[portNUM_PROCESSORS];
static StackType_t s_timer_task_stack[portNUM_PROCESSORS][configMINIMAL_STACK_SIZE];void start_scheduler(int core_id);int __attribute__((weak)) configure_fpioa()
{return 0;
}static void main_thunk(void *p)
{/* Register finalization function */atexit(__libc_fini_array);/* Init libc array for C++ */__libc_init_array();install_hal();install_drivers();configure_fpioa();main_thunk_param_t *param = (main_thunk_param_t *)p;param->ret = param->user_main(0, 0);
}static void os_entry_core1()
{clear_csr(mie, MIP_MTIP);clint_ipi_enable();set_csr(mstatus, MSTATUS_MIE);vTaskStartScheduler();
}int os_entry(int (*user_main)(int, char **))
{clear_csr(mie, MIP_MTIP);clint_ipi_enable();set_csr(mstatus, MSTATUS_MIE);TaskHandle_t mainTask;main_thunk_param_t param = {};param.user_main = user_main;if (xTaskCreate(main_thunk, "Core 0 Main", configMAIN_TASK_STACK_SIZE, &param, configMAIN_TASK_PRIORITY, &mainTask) != pdPASS){return -1;}core_sync_awaken((uintptr_t)os_entry_core1);vTaskStartScheduler();return param.ret;
}void vApplicationIdleHook(void)
{
}void vApplicationGetIdleTaskMemory(StaticTask_t **ppxIdleTaskTCBBuffer, StackType_t **ppxIdleTaskStackBuffer, uint32_t *pulIdleTaskStackSize)
{UBaseType_t uxPsrId = uxPortGetProcessorId();/* Pass out a pointer to the StaticTask_t structure in which the Idle task'sstate will be stored. */*ppxIdleTaskTCBBuffer = &s_idle_task[uxPsrId];/* Pass out the array that will be used as the Idle task's stack. */*ppxIdleTaskStackBuffer = s_idle_task_stack[uxPsrId];/* Pass out the size of the array pointed to by *ppxIdleTaskStackBuffer.Note that, as the array is necessarily of type StackType_t,configMINIMAL_STACK_SIZE is specified in words, not bytes. */*pulIdleTaskStackSize = configMINIMAL_STACK_SIZE;
}void vApplicationGetTimerTaskMemory(StaticTask_t **ppxTimerTaskTCBBuffer, StackType_t **ppxTimerTaskStackBuffer, uint32_t *pulTimerTaskStackSize)
{UBaseType_t uxPsrId = uxPortGetProcessorId();/* Pass out a pointer to the StaticTask_t structure in which the Idle task'sstate will be stored. */*ppxTimerTaskTCBBuffer = &s_timer_task[uxPsrId];/* Pass out the array that will be used as the Idle task's stack. */*ppxTimerTaskStackBuffer = s_timer_task_stack[uxPsrId];/* Pass out the size of the array pointed to by *ppxIdleTaskStackBuffer.Note that, as the array is necessarily of type StackType_t,configMINIMAL_STACK_SIZE is specified in words, not bytes. */*pulTimerTaskStackSize = configTIMER_TASK_STACK_DEPTH;
}void vApplicationStackOverflowHook(TaskHandle_t xTask, char *pcTaskName)
{configASSERT(!"Stackoverflow !");
}

我们看到os_entry这个函数里面调用了vTaskStartScheduler，并且在调用之前，创建了一个main_thunk任务并且同时调用core_sync_awaken((uintptr_t)os_entry_core1);这个os_entry_core1内部又调用了vTaskStartScheduler，开启了core 1的多任务调度。main_thunk任务内部执行了一些系统初始化操作（hal/drivers/fpioa）,然后执行user_main函数，这个函数就是os_entry函数的入参，我们继续跟踪，发现lib/bsp/entry_user.c这个里面的_init_bsp调用了os_entry(main)，此处的main即src/hello_world/main.c里面main函数，另外通过汇编代码跟踪，我们发现lib/bsp/crt.S这个里面调用了_init_bsp。

至此我们完成了整个系统rtos的启动过程。

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