RK2706播放器filesystem

发布于 2011-11-05 10:13:57 浏览：7601 订阅该版

对于filesystem部分,建议大家都多去看看bsp下stm32f10x与mini2440分支SD部分.
这里参考了bsp下stm32f10x的sdcard.c.

熟悉RT-Thread的朋友肯定会知道有`rt_hw_sdcard_init()`这么一函数.
此函数负责初试化底层SDIO相关寄存器接着读取第0扇区传给dfs以获得最后第一分区信息,最后向RT-Thread注册sdcard这Block设备.

综上,如果只要求filesystem跑起来的话,只需实现开始的底层SD/MMC相关寄存器配置与读扇区函数就行.

先看实现了初始化SD/MMC相关寄存器的函数
```c
int sd_init(void)
{
	int ret;

rt_sem_init(&transfer_completion_signal, "t_com", 0, RT_IPC_FLAG_FIFO);
	rt_sem_init(&command_completion_signal, "c_com", 0, RT_IPC_FLAG_FIFO);
	rt_mutex_init(&sd_mtx,"sd_init",RT_IPC_FLAG_FIFO);

/* 初始化 SD/MMC 相关寄存器 */
	init_controller();

/* 初始化 SD/MMC 卡 */
	ret = sd_init_card();

if (ret < 0)
	{
		rt_kprintf("SD init fail!! the ret is : 0x%x
",ret);
		return ret;
	}

return 0;
}
```

这里值得注意的是transfer_completion_signal与command_completion_signal信号量,顾名思义是数据发送完成信号与命令发送完成信号.
这意味着向SD/MMC发送命令与数据都得等待各自完成信号(会在中断上释放各自信号量).

现阶段暂时无法改为轮询方式.
对于sd_init_card()的兼容性也有待验证,分别测试了1G与4G TF卡都可成功初始化问题.
成功初试化后便可读扇区了.
```c
static __inline void read_sd_data(unsigned char **dst)
{
	commit_discard_dcache_range((const void *)*dst, 512);

A2A_IDST0 = (unsigned long)*dst;
	A2A_CON0  = (3<<9) |    /* burst 16 */
	            (1<<6) |    /* fixed src */
	            (1<<3) |    /* DMA start */
	            (2<<1) |    /* word transfer size */
	            (1<<0);     /* software mode */

/* wait for DMA engine to finish transfer */
	while (A2A_DMA_STS & 1);

*dst += 512;
}

int sd_read_sectors(unsigned long start, void* buf,int count)
{
	unsigned long response;
	unsigned int retry_cnt = 0;
	int cnt, ret = 0;
	unsigned char *dst;

sd_enable(true);

if (count <= 0 || start + count > card_info.numblocks)
		return -1;

if (!(card_info.ocr & (1<<30)))
		start <<= 9; /* not SDHC */

while (retry_cnt++ < 20)
	{
		cnt = count;
		dst = (unsigned char *)buf;

ret = 0;
		retry = false;       /* reset retry flag */

mmu_buff_reset();

if (cnt == 1)
		{
			/* last block to transfer */
			SD_DATAT = DATA_XFER_START | DATA_XFER_READ |
			           DATA_BUS_1LINE | DATA_XFER_DMA_DIS |
			           DATA_XFER_SINGLE;

}
		else
		{
			/* more than one block to transfer */
			SD_DATAT = DATA_XFER_START | DATA_XFER_READ |
			           DATA_BUS_1LINE | DATA_XFER_DMA_DIS |
			           DATA_XFER_MULTI;
		}

/* issue read command to the card */
		if (!send_cmd(SD_READ_MULTIPLE_BLOCK, start, RES_R1, &response))
		{
			ret = -2;
			continue;
		}

while (cnt > 0)
		{
			/* wait for transfer completion */
			rt_sem_take(&transfer_completion_signal,RT_WAITING_FOREVER);

if (retry)
			{
				/* data transfer error */
				ret = -3;
				break;
			}

/* exchange buffers */
			mmu_switch_buff();

cnt--;

if (cnt == 0)
			{
				if (!send_cmd(SD_STOP_TRANSMISSION, 0, RES_R1b, &response))
					ret = -4;

read_sd_data(&dst);

break;
			}
			else if (cnt == 1)
			{
				/* last block to transfer */
				SD_DATAT = DATA_XFER_START | DATA_XFER_READ |
				           DATA_BUS_1LINE | DATA_XFER_DMA_DIS |
				           DATA_XFER_SINGLE;

read_sd_data(&dst);

}
			else
			{
				/* more than one block to transfer */
				SD_DATAT = DATA_XFER_START | DATA_XFER_READ |
				           DATA_BUS_1LINE | DATA_XFER_DMA_DIS |
				           DATA_XFER_MULTI;

read_sd_data(&dst);
			}

} /* while (cnt > 0) */

/* transfer successfull - leave retry loop */
		if (ret == 0)
			break;

} /* while (retry_cnt++ < 20) */

sd_enable(false);

return ret;
}
```

这里值得一说的是`read_sd_data(&dst)`函数,此函数会调用`commit_discard_dcache_range()`清除目标地址+512范围的cache,以保证DMA过程数据正确.
实现读扇区函数后,便是向RT-Thread注册sdcard这Block设备了,这里填充相应函数即可.
```c
static rt_size_t rt_sdcard_read(rt_device_t dev, rt_off_t pos, void* buffer, rt_size_t size)
{
	rt_uint32_t nr = size, retry;
	rt_err_t err;

rt_mutex_take(&sd_mtx,RT_WAITING_FOREVER);

err = sd_read_sectors((part.offset+pos),(rt_uint32_t*)buffer,size);

rt_mutex_release(&sd_mtx);

if (err == RT_EOK) return size;

return 0;
}

void rt_hw_sdcard_init()
{
	if (sd_init() == RT_EOK)
	{
		rt_uint8_t *sector;
		rt_err_t   status;

/* get the first sector to read partition table */
		sector = (rt_uint8_t*) rt_malloc (512);
		if (sector == RT_NULL)
		{
			rt_kprintf("allocate partition sector buffer failed
");
			return;
		}
		status = sd_read_sectors(0, (rt_uint32_t*)sector, 1);
		if (status == RT_EOK)
		{
			/* get the first partition */
			if (dfs_filesystem_get_partition(&part, sector, 0) != 0)
			{
				/* there is no partition */
				part.offset = 0;
				part.size   = 0;
			}
		}
		else
		{
			/* there is no partition table */
			part.offset = 0;
			part.size   = 0;
		}

/* release sector buffer */
		rt_free(sector);

/* register sdcard device */
		sdcard_device.type  = RT_Device_Class_Block;
		sdcard_device.init 	= rt_sdcard_init;
		sdcard_device.open 	= rt_sdcard_open;
		sdcard_device.close = rt_sdcard_close;
		sdcard_device.read 	= rt_sdcard_read;
		sdcard_device.write = rt_sdcard_write;
		sdcard_device.control = rt_sdcard_control;

/* no private */
		sdcard_device.user_data = &card_info;

rt_device_register(&sdcard_device, "sd0",
		                   RT_DEVICE_FLAG_RDWR | RT_DEVICE_FLAG_REMOVABLE | RT_DEVICE_FLAG_STANDALONE);

return;
	}

__return:
	rt_kprintf("sdcard init failed
");

}
```

最后值得注意的是filesystem配置的问题,由于架构原因,rtconfig.h中不能定义`RT_DFS_ELM_WORD_ACCESS`此宏.
如无意外,SD/MMC已经mount成功,顺带加入readspeed.c测速.
![read_speed.jpg](/uploads/2304_46f0beef05c5897f0debc9400313d458.jpg)
![sd_card.rar](/uploads/2304_02d582bb789291b0ee6ee8f7a46ed08e.rar)