[SDIO] SD card 初始化及常用命令解析（附波形，uboot代码）


目录

初始化

1.cmd 0

2.cmd8

3.cmd55

4.acmd41

5.cmd2

6.cmd3

7.cmd9

8.cmd13

9.cmd7

10.ACMD51

11.CMD6

12.CMD16

13.CMD17

14.CMD18

15.CMD12

tuning

CMD19

DW_SDHCI的tuning流程

初始化

1.cmd 0

/* Reset the Card */

err = mmc_go_idle(mmc);

static int mmc_go_idle(struct mmc *mmc)

{

struct mmc_cmd cmd;

int err;

usleep(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;

usleep(2000);

return 0;

}

2.cmd8

R7:

/* Test for SD version 2 */

err = mmc_send_if_cond(mmc);

static int mmc_send_if_cond(struct mmc *mmc)

{

struct mmc_cmd cmd;

int err;

cmd.cmdidx = SD_CMD_SEND_IF_COND;

/* We set the bit if the host supports voltages between 2.7 and 3.6 V */

cmd.cmdarg = ((mmc->cfg->voltages & 0xff8000) != 0) << 8 | 0xaa;

cmd.resp_type = MMC_RSP_R7;

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

if (err)

return err;

if ((cmd.response[0] & 0xff) != 0xaa)

{

debug("UNUSABLE_ERR mmc_send_if_cond\n");

return UNUSABLE_ERR;

}

else

mmc->version = SD_VERSION_2;

return 0;

}

3.cmd55

ACMD:SD card application-specific commands.

在发所有的ACMD之前，需要先发APP_CMD（CMD55）通知SD卡下一个指令为ACMD。SD卡应答R1，然后才能发送ACMD。

cmd.cmdidx = MMC_CMD_APP_CMD;

cmd.resp_type = MMC_RSP_R1;

cmd.cmdarg = 0;

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

4.acmd41

卡片的初始化将在主机发送ACMD41命令后开始，主机每间隔1秒就发送一次 ACMD41 命令，直到初始化完成（OCR 寄存器的 bit31 置位）。

（bit 31）指示卡片的上电操作是否完成

（bit 30）指示卡片的容量状态（0代表SDSC、1代表SDHC或者SDXC）

上图OCR （bit 31）为0，即为卡busy

上图OCR （bit 31）为1，即为卡初始化完成

static int sd_send_op_cond(struct mmc *mmc) //send acmd41-- get ocr data

{

int timeout = 1000;

int err;

struct mmc_cmd cmd;

while (1)

{

cmd.cmdidx = MMC_CMD_APP_CMD;

cmd.resp_type = MMC_RSP_R1;

cmd.cmdarg = 0;

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

if (err)

return err;

cmd.cmdidx = SD_CMD_APP_SEND_OP_COND;

cmd.resp_type = MMC_RSP_R3;

/*

* Most cards do not answer if some reserved bits

* in the ocr are set. However, Some controller

* can set bit 7 (reserved for low voltages), but

* how to manage low voltages SD card is not yet

* specified.

*/

cmd.cmdarg = mmc_host_is_spi(mmc) ? 0 :

(mmc->voltages & 0xff8000);

if (mmc->version == SD_VERSION_2)

cmd.cmdarg |= OCR_HCS;

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

if (err)

return err;

if (cmd.response[0] & OCR_BUSY)//等待OCR[31]置1后跳出循环，完成初始化。

break;

if (timeout-- <= 0)

return -EOPNOTSUPP;

usleep(1000);

}

5.cmd2

CMD2，验证SD卡是否接入，获取(CID)

/* 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((void*)mmc->cid, (void*)cmd.response, 16);

6.cmd3

读取卡相对地址RCA, 当卡收到RCA(CMD3)后，卡就会进入数据传输模式。

/*

* For MMC cards, set the Relative Address.

* For SD cards, get the Relatvie Address.

* This also puts the cards into Standby State

*/

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;

}

7.cmd9

CMD9，读取CSD寄存器获取卡的相关信息

RCA是之前CMD3读取到的卡RCA

PS：R2回复CMD9时为CSD，回复CMD2时为CID

CSD（具体信息）寄存器也是 128 bits，提供了访问卡片内容的一些信息如：传输速率、数据格式、错误类型、最大是数据访问时间、DSR 寄存器是否启用的。其中 bit[126:127] 记录了 CSD 的版本号，CSD version 1.0 为标准容量卡所用，CSD version 2.0 为大容量或超大容量卡所用

---------------------

8.cmd13

读取卡状态

RCA是之前CMD3读取到的卡RCA

9.cmd7

发送CMD7+RCA选中卡片, 发送CMD7+0不选中卡片，RCA是之前CMD3读取到的卡RCA

/* 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;

}

10.ACMD51

发送CMD55+ACMD51读取SCR寄存器，SD卡可以通过该值获得位宽，如果是MMC卡则需要使用主线测试来确定卡的位宽。

PS：slave回复ACMD51是R1+data。SCR 是放在data中的，一共8个字节。

cmd.cmdidx = SD_CMD_APP_SEND_SCR;//51

cmd.resp_type = MMC_RSP_R1;

cmd.cmdarg = 0;

timeout = 3;

retry_scr:

data.dest = (char *)mmc->scr;

data.blocksize = 8;

data.blocks = 1;

data.flags = MMC_DATA_READ;

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

if (err) {

if (timeout--)

goto retry_scr;

return err;

}

mmc->scr[0] = __be32_to_cpu(mmc->scr[0]);

mmc->scr[1] = __be32_to_cpu(mmc->scr[1]);

// debug("scr_0=0x%x scr_1=0x%x\n",mmc->scr[0],mmc->scr[1]);

switch ((mmc->scr[0] >> 24) & 0xf) {//SD_SPEC

case 0:

mmc->version = SD_VERSION_1_0;

break;

case 1:

mmc->version = SD_VERSION_1_10;

break;

case 2:

mmc->version = SD_VERSION_2;

if ((mmc->scr[0] >> 15) & 0x1)

mmc->version = SD_VERSION_3;

break;

default:

mmc->version = SD_VERSION_1_0;

break;

}

if (mmc->scr[0] & SD_DATA_4BIT)

mmc->card_caps |= MMC_MODE_4BIT;

11.CMD6

CMD6是SD卡速度模式切换的一个重要命令，它定义了4种不同的功能组：

  1. 访问模式：SD总线接口速度模式的选择；
  2. 命令系统：通过一套莫共有的命令来扩展和控制特定的功能；
  3. 驱动强度：在UHS-I模式下等选择合适的输出驱动强度，和主机环境相关；
  4. 电流/功率限制：UHS-I卡在UHS-I模式选择，和主机环境相关；

https://upload-images.jianshu.io/upload_images/726783-0f3f6c64bd8b7f0a.png?imageMogr2/auto-orient/

MODE0: 查询模式，卡返回R1 + data[511:0]

data中存放了卡对每种功能的支持情况及当前选中的功能状态，及忙状态。

MODE1: 切换模式

每次发送切换只能选中一个功能组进行切换，其他功能组全部为1.

static int sd_switch(struct mmc *mmc, int mode, int group, u8 value, u8 *resp)

{

struct mmc_cmd cmd;

struct mmc_data data;

/* Switch the frequency */

cmd.cmdidx = SD_CMD_SWITCH_FUNC;

cmd.resp_type = MMC_RSP_R1;

cmd.cmdarg = (mode << 31) | 0xffffff;

cmd.cmdarg &= ~(0xf << (group << 2));

cmd.cmdarg |= value << (group << 2);

data.dest = (char *)resp;

data.blocksize = 64;

data.blocks = 1;

data.flags = MMC_DATA_READ;

return mmc_send_cmd(mmc, &cmd, &data);

}

12.CMD16

设置块大小

13.CMD17

读单个块参数为block地址

卡回复R1 +DATA

14.CMD18

读多块

15.CMD12

停止传输

tuning

CMD19

发送tuning block

host发送CMD19，卡回复R1+data，tuning data 的数据长度及内容是固定的，host可以根据收到的数据调整采样的timing。

DW_SDHCI的tuning流程