sd卡热插拔时初始化失败的bug

发布于 2022-05-13 01:14:20 浏览：747 订阅该版

在测试SD卡反复热插拔时出现SD卡无法顺利初始化的情况，初始化程序挂起并进入idle，输出日志如下：
```
 \ | /
- RT -     Thread Operating System
 / | \     4.1.0 build May 13 2022 00:40:03
 2006 - 2022 Copyright by RT-Thread team
I/I2C main: I2C bus [i2c1] registered
ADC1_3 init success!
msh />I/SDIO mmcsd_detect: SD card capacity 3872256 KB.
I/SDIO mmcsd_detect: switching card to high speed failed!
found part[0], begin: 4194304, size: 3.705GB
dfs mount sd0 success
SD card eject!
SD card insert!
SD card eject!
I/SDIO mmcsd_detect: SD card capacity 3872256 KB.
SD card insert!
SD card eject!
```
通过在RT1061上debug不断查找问题，发现在sd.c文件中mmcsd_send_app_op_cond函数卡死，通过将mmcsd_send_app_cmd命令尝试次数改为1000可以解决热插拔卡时可能由于电源不稳定造成的初始化失败，修改后的代码为：
```c
rt_err_t mmcsd_send_app_op_cond(struct rt_mmcsd_host *host,
                                rt_uint32_t           ocr,
                                rt_uint32_t          *rocr)
{
    struct rt_mmcsd_cmd cmd;
    rt_uint32_t i;
    rt_err_t err = RT_EOK;

rt_memset(&cmd, 0, sizeof(struct rt_mmcsd_cmd));

cmd.cmd_code = SD_APP_OP_COND;
    if (controller_is_spi(host))
        cmd.arg = ocr & (1 << 30); /* SPI only defines one bit */
    else
        cmd.arg = ocr;
    cmd.flags = RESP_SPI_R1 | RESP_R3 | CMD_BCR;

for (i = 1000; i; i--)			//改为1000，防止重新插卡时失败
    {
        err = mmcsd_send_app_cmd(host, RT_NULL, &cmd, 3);
        if (err)
			break;

/* if we're just probing, do a single pass */
        if (ocr == 0)
            break;

/* otherwise wait until reset completes */
        if (controller_is_spi(host))
        {
            if (!(cmd.resp[0] & R1_SPI_IDLE))
                break;
        }
        else
        {
            if (cmd.resp[0] & CARD_BUSY)
                break;
        }

err = -RT_ETIMEOUT;

mmcsd_delay_ms(10); //delay 10ms
    }

if (rocr && !controller_is_spi(host))
        *rocr = cmd.resp[0];

return err;
}
```
里面的i由初始值100改为1000，修改后的输出：
```
 \ | /
- RT -     Thread Operating System
 / | \     4.1.0 build May 13 2022 00:40:03
 2006 - 2022 Copyright by RT-Thread team
I/I2C main: I2C bus [i2c1] registered
ADC1_3 init success!
msh />I/SDIO mmcsd_detect: SD card capacity 3872256 KB.
I/SDIO mmcsd_detect: switching card to high speed failed!
found part[0], begin: 4194304, size: 3.705GB
dfs mount sd0 success
SD card eject!
SD card insert!
I/SDIO mmcsd_detect: SD card capacity 3872256 KB.
I/SDIO mmcsd_detect: switching card to high speed failed!
found part[0], begin: 4194304, size: 3.705GB
SD card eject!
SD card insert!
I/SDIO mmcsd_detect: SD card capacity 3872256 KB.
I/SDIO mmcsd_detect: switching card to high speed failed!
found part[0], begin: 4194304, size: 3.705GB
SD card eject!
```
经反复测试，SD卡初始化不再出现失败情况