IMX6UL eMMC命令分析

 

 

CMD0 RESET

发送CMD0 eMMC会进入自行复位busy状态后进入idle状态

	#define MMC_CMD_GO_IDLE_STATE		0	

	struct mmc_cmd cmd;
	int err;
	udelay(1000);

	cmd.cmdidx = MMC_CMD_GO_IDLE_STATE;
	cmd.cmdarg = 0;
	cmd.resp_type = MMC_RSP_NONE;

	err = mmc_send_cmd(mmc, &cmd, NULL);
	if (err)
		return err;
	udelay(2000);

CMD1 CHECK_BUSY

CMD1命令得到eMMC的OCR寄存器值

代码发送命令，bit[31]为1表示ready状态，为0表示busy状态

	#define MMC_CMD_SEND_OP_COND		1

	cmd.cmdidx = MMC_CMD_SEND_OP_COND;
	cmd.resp_type = MMC_RSP_R3;
	cmd.cmdarg = 0;
	if (use_arg && !mmc_host_is_spi(mmc))
		cmd.cmdarg = OCR_HCS |
			(mmc->cfg->voltages &
			(mmc->ocr & OCR_VOLTAGE_MASK)) |
			(mmc->ocr & OCR_ACCESS_MODE);

	err = mmc_send_cmd(mmc, &cmd, NULL);
	if (err)
		return err;
	mmc->ocr = cmd.response[0];

CMD2 GET_CID

发送CMD2进行认证（获取CID），寄存器描述，128比特，16字节

代码发送命令 

	#define MMC_CMD_ALL_SEND_CID		2

        /* Put the Card in Identify Mode */
	cmd.cmdidx = mmc_host_is_spi(mmc) ? MMC_CMD_SEND_CID :
		MMC_CMD_ALL_SEND_CID; /* cmd not supported in spi */
	cmd.resp_type = MMC_RSP_R2;
	cmd.cmdarg = 0;

	err = mmc_send_cmd(mmc, &cmd, NULL);

	if (err)
		return err;

	memcpy(mmc->cid, cmd.response, 16);

打印出CID数据

	printf("Manufacturer ID: %x\n", mmc->cid[0] >> 24);
	printf("OEM: %x\n", (mmc->cid[0] >> 8) & 0xffff);
	printf("Name: %c%c%c%c%c \n", mmc->cid[0] & 0xff,
			(mmc->cid[1] >> 24), (mmc->cid[1] >> 16) & 0xff,
			(mmc->cid[1] >> 8) & 0xff, mmc->cid[1] & 0xff);

	Manufacturer ID: fe
	OEM: 14e
	Name: P1XXX 

CMD3 STBY

然后发送CMD3，之后eMMC进入stby状态

        #define SD_CMD_SEND_RELATIVE_ADDR	3

	if (!mmc_host_is_spi(mmc)) { /* cmd not supported in spi */
		cmd.cmdidx = SD_CMD_SEND_RELATIVE_ADDR;
		cmd.cmdarg = mmc->rca << 16;
		cmd.resp_type = MMC_RSP_R6;

		err = mmc_send_cmd(mmc, &cmd, NULL);

		if (err)
			return err;

		if (IS_SD(mmc))
			mmc->rca = (cmd.response[0] >> 16) & 0xffff;
	}

CMD7

使用CMD7进入transfer状态，此命令用来设置eMMC的状态，因为当使用CMD0使eMMC复位后，eMMC处于idle或pre_idle状态，如果需要数据传输，必须将eMMC置于transfer_state

	#define MMC_CMD_SELECT_CARD		7

	/* Select the card, and put it into Transfer Mode */
	if (!mmc_host_is_spi(mmc)) { /* cmd not supported in spi */
		cmd.cmdidx = MMC_CMD_SELECT_CARD;
		cmd.resp_type = MMC_RSP_R1;
		cmd.cmdarg = mmc->rca << 16;
		err = mmc_send_cmd(mmc, &cmd, NULL);

		if (err)
			return err;
	}

 CMD8 

CMD8命令用来获取EXT_CSD的值，虽然回复为R1，但是EXT_CSD的512字节值会被读取并存储到内存里，然后用户可以根据这些数据分析出eMMC当前支持的各种参数和状态,EXT_CSD是eMMC4之后才引入的寄存器组

	struct mmc_cmd cmd;
	struct mmc_data data;
	int err;

	/* Get the Card Status Register */
	cmd.cmdidx = MMC_CMD_SEND_EXT_CSD;
	cmd.resp_type = MMC_RSP_R1;
	cmd.cmdarg = 0;

	data.dest = (char *)ext_csd;
	data.blocks = 1;
	data.blocksize = MMC_MAX_BLOCK_LEN;
	data.flags = MMC_DATA_READ;

	err = mmc_send_cmd(mmc, &cmd, &data);

CMD9 GET_CSD

获取CSD寄存器值，描述如下

代码实现 

	#define MMC_CMD_SEND_CSD		9

	/* Get the Card-Specific Data */
	cmd.cmdidx = MMC_CMD_SEND_CSD;
	cmd.resp_type = MMC_RSP_R2;
	cmd.cmdarg = mmc->rca << 16;

	err = mmc_send_cmd(mmc, &cmd, NULL);

	/* Waiting for the ready status */
	mmc_send_status(mmc, timeout);

	if (err)
		return err;

	mmc->csd[0] = cmd.response[0];
	mmc->csd[1] = cmd.response[1];
	mmc->csd[2] = cmd.response[2];
	mmc->csd[3] = cmd.response[3];