本文主要是介绍i.mx6q u-boot2016.03移植笔记，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
使用主板：迅为i.mx6q开发板，2G DDR
参考文献：
fsl-yocto-L4.1.15_2.0.0-ga
IMXBSPPG Rev. 1, 01/2017
1.参考i.MX_BSP_Porting_Guide.pdf移植，说明比较详细，参考的是官方imx6sabresd开发板
2.修改DCD TABLE，此处参考迅为i.mx6q开发板提供的u-boot 2009版本源码，u-boot 2009和u-boot 2016对DCD配置写法有区别，但数值完全可以一致
3.按照i.MX_BSP_Porting_Guide.pdf编写build_u-boot.sh并执行
4.首次运行出现以下错误
Can't find PMIC:PFUZE100
initcall sequence 8ff97484 failed at call 178041ac (err=-19)
### ERROR ### Please RESET the board ###
原因是开发板没有用nxp的pmic所以检测不到pmic，修改方法如下：
a.include/configs/mx6_common.h 去掉#define CONFIG_LDO_BYPASS_CHECK
b.修改include/configs/mx6sabre_common.h 去掉pmic下的4个#define
c.屏蔽/board/freecale/<board>/<board>.c中的power_init_board函数
5.烧写SD，u-boot文件夹下，命令如下
sudo dd if=u-boot.imx of=/dev/sdx bs=512 seek=2 conv=fsync
6.开发板拨码SD启动，插入SD卡，开电源
U-Boot 2016.03 (Sep 22 2018 - 16:49:18 +0800)
CPU: Freescale i.MX6Q rev1.5 996 MHz (running at 792 MHz)
CPU: Extended Commercial temperature grade (-20C to 105C) at 45C
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
*** Warning - MMC init failed, using default environment
No panel detected: default to Hannstar-XGA
Display: Hannstar-XGA (1024x768)
In: serial
Out: serial
Err: serial
MMC: no card present
Net: Board Net Initialization Failed
No ethernet found.
Normal Boot
Hit any key to stop autoboot: 0
MMC: no card present
MMC: no card present
Booting from net ...
No ethernet found.
No ethernet found.
Bad Linux ARM zImage magic!
=>
7 修改include/configs/<board>.h中的define，参考i.MX Linux user's guide中几个usdhc的定义
#define CONFIG_MMCROOT "/dev/mmcblk1p2" /* SDHC2 */
#define CONFIG_SYS_MMC_ENV_DEV 1
8.修改SD卡引脚配置
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 */
};
9.遇到No Card prent问题，检测不到SD卡插入，修改board_mmc_getcd函数适应itopeet i.mx6Q
至此u-boot可正常检测出SD卡：
=> mmc info
Device: FSL_SDHC
Manufacturer ID: 12
OEM: 3456
Name: SDTran Speed: 50000000
Rd Block Len: 512
SD version 3.0
High Capacity: Yes
Capacity: 7.4 GiB
Bus Width: 4-bit
Erase Group Size: 512 Bytes
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