项目场景：

讯为的IMX6Q开发板2G+16G配置

ubuntu18.04环境

讯为android6.0源码

问题描述：

使用讯为官方Android6.0源码编译uboot，通过TF卡启动，报错MMC: no card present/MMC init failed

求助讯为官方支持无果，只好自己琢磨了，报错内容如下

U-Boot 2015.04 (Feb 23 2022 - 17:31:04)

CPU:   Freescale i.MX6Q rev1.5 at 792 MHz
CPU:   Temperature 17 C
Reset cause: POR
Board: MX6-SabreSD
I2C:   ready
DRAM:  2 GiB
MMC:   FSL_SDHC: 0, FSL_SDHC: 1, FSL_SDHC: 2
MMC: no card present
MMC init failed
Using default environment

*** Warning use default panel:9.7 ***
MMC: no card present
MMC init failed
LCD type:9.7
MMC: no card present
MMC init failed
bootsystem:android
bootargs=console=ttymxc0,115200 androidboot.console=ttymxc0 consoleblank=0 vmalloc=256M init=/init video=mxcfb0:dev=ldb,VGA_1024768 video=mxcfb1:off video=mxcfb2:off video=mxcfb3:off androidboot.hardware=freescale cma=384M
Display: 9.7 (1024x768)
In:    serial
Out:   serial
Err:   serial
MMC: no card present
Net:   FEC [PRIME]
Normal Boot
Hit any key to stop autoboot:  0

原因分析及解决：

通过网上搜索资料，大概确定是因为SD卡的CD引脚未正常检测到的原来，查看mx6sabresd.c文件，发现SD卡引脚配置如下

static iomux_v3_cfg_t const usdhc2_pads[] = {
	MX6_PAD_SD2_CLK__SD2_CLK	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_SD2_CMD__SD2_CMD	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_SD2_DAT0__SD2_DATA0	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_SD2_DAT1__SD2_DATA1	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_SD2_DAT2__SD2_DATA2	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_SD2_DAT3__SD2_DATA3	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_NANDF_D4__SD2_DATA4	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_NANDF_D5__SD2_DATA5	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_NANDF_D6__SD2_DATA6	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_NANDF_D7__SD2_DATA7	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_NANDF_D2__GPIO2_IO02	| MUX_PAD_CTRL(NO_PAD_CTRL), /* CD */

};

配置的是MX6_PAD_NANDF_D2__GPIO2_IO02 引脚，然后查看原理图发现如下



CD引脚为KEY_COL7，继续查找，核心板连接如下



问题就出现了，核心板连接的是GPIO_4，然后查看手册发现



正确引脚应该是GPIO1_4，所以修改mx6sabresd.c文件如下

static iomux_v3_cfg_t const usdhc2_pads[] = {
	MX6_PAD_SD2_CLK__SD2_CLK	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_SD2_CMD__SD2_CMD	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_SD2_DAT0__SD2_DATA0	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_SD2_DAT1__SD2_DATA1	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_SD2_DAT2__SD2_DATA2	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_SD2_DAT3__SD2_DATA3	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_NANDF_D4__SD2_DATA4	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_NANDF_D5__SD2_DATA5	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_NANDF_D6__SD2_DATA6	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
	MX6_PAD_NANDF_D7__SD2_DATA7	| MUX_PAD_CTRL(USDHC_PAD_CTRL),
//	MX6_PAD_NANDF_D2__GPIO2_IO02	| MUX_PAD_CTRL(NO_PAD_CTRL), /* CD */
	MX6_PAD_GPIO_4__GPIO1_IO04	| MUX_PAD_CTRL(NO_PAD_CTRL), /* CD */
};

#define USDHC2_CD_GPIO	IMX_GPIO_NR(1, 4)
#define USDHC3_CD_GPIO	IMX_GPIO_NR(2, 0)

修改之后重新编译，再烧写uboot到sd卡，上电启动终于正常了

U-Boot 2015.04 (Feb 23 2022 - 18:07:20)

CPU:   Freescale i.MX6Q rev1.5 at 792 MHz
CPU:   Temperature 36 C
Reset cause: POR
Board: MX6-SabreSD
I2C:   ready
DRAM:  2 GiB
MMC:   FSL_SDHC: 0, FSL_SDHC: 1, FSL_SDHC: 2
LCD type:9.7
bootsystem:android
bootargs=console=ttymxc0,115200 androidboot.console=ttymxc0 consoleblank=0 vmalloc=256M init=/init video=mxcfb0:dev=ldb,VGA_1024768 video=mxcfb1:off video=mxcfb2:off video=mxcfb3:off androidboot.hardware=freescale cma=384M
Display: 9.7 (1024x768)
In:    serial
Out:   serial
Err:   serial
switch to partitions #0, OK
mmc0 is current device
Net:   FEC [PRIME]
Normal Boot
Hit any key to stop autoboot:  0
=> mmc info
Device: FSL_SDHC
Manufacturer ID: 0
OEM: 0
Name: SMISD
Tran Speed: 50000000
Rd Block Len: 512
SD version 1.10
High Capacity: No
Capacity: 477.5 MiB
Bus Width: 4-bit
Erase Group Size: 512 Bytes
=> mmc list
FSL_SDHC: 0 (SD)
FSL_SDHC: 1
FSL_SDHC: 2
=>

大功告成，哈哈