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：
- 访问模式：SD总线接口速度模式的选择；
- 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；
- 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；
- 电流/功率限制：UHS-I卡在UHS-I模式选择，和主机环境相关；
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
