我imx6ull使用的是正点原子的alpha开发板。我将我的SD卡分成了两个分区，第一个分区格式化为fat，用来存放zImage和dtb；第二个分区格式化为EXT4格式，这个分区作为根文件系统。

遇到的问题是：我编译好kernel后，尝试通过UBoot的fatload或load命令将fat分区中的boot/zImage和boot/my-i6ull.dtb文件载入内存，但是每次载入zImage的时候都无法读取这个文件，再次读取时就报找不到分区表：

U-Boot 2016.03-gc221d3f (Oct 14 2019 - 12:40:04 +0800)

CPU:   Freescale i.MX6ULL rev1.1 69 MHz (running at 396 MHz)
CPU:   Industrial temperature grade (-40C to 105C) at 49C
Reset cause: POR
Board: MX6ULL 14x14 EVK
I2C:   ready
DRAM:  256 MiB
NAND:  512 MiB
MMC:   FSL_SDHC: 0
*** Warning - bad CRC, using default environment

Display: ATK-LCD-4.3-480x272 (480x272)
Video: 480x272x24

NAND read: device 0 offset 0x420000, size 0x100000
 1048576 bytes read: OK
Error: no valid bmp image at 88000000
In:    serial
Out:   serial
Err:   serial
Net:   FEC1
Error: FEC1 address not set.

Normal Boot
Hit any key to stop autoboot:  0
=> mmc part

Partition Map for MMC device 0  --   Partition Type: DOS

Part    Start Sector    Num Sectors     UUID            Type
  1     2048            204800          8bb1460b-01     0e Boot
  2     206848          772096          8bb1460b-02     83
=> fatls mmc 0:1 boot
            ./
            ../
  5583352   zimage
    36274   my-i6ull.dtb

2 file(s), 2 dir(s)

=> fatload mmc 0:1 80800000 boot/zImage
reading boot/zImage
Error reading cluster
** Unable to read file boot/zImage **
=>
=> fatload mmc 0:1 80800000 boot/zImage
** Can't read partition table on 0:0 **
** Invalid partition 1 **
=>
=> mmc part

Partition Map for MMC device 0  --   Partition Type: DOS

Part    Start Sector    Num Sectors     UUID            Type
** Can't read partition table on 0:0 **
=>

令我感到神奇的是boot/my-iu6ull.dtb文件虽然大多数时候也是读取失败，但偶尔也能成功读到内存中去。等boot/my-i6ull.dtb读完后仍能通过 mmc part 看到分区表，但这时，如果尝试读zImage，仍然是失败：

U-Boot 2016.03-gc221d3f (Oct 14 2019 - 12:40:04 +0800)

CPU:   Freescale i.MX6ULL rev1.1 69 MHz (running at 396 MHz)
CPU:   Industrial temperature grade (-40C to 105C) at 50C
Reset cause: POR
Board: MX6ULL 14x14 EVK
I2C:   ready
DRAM:  256 MiB
NAND:  512 MiB
MMC:   FSL_SDHC: 0
*** Warning - bad CRC, using default environment

Display: ATK-LCD-4.3-480x272 (480x272)
Video: 480x272x24

NAND read: device 0 offset 0x420000, size 0x100000
 1048576 bytes read: OK
Error: no valid bmp image at 88000000
In:    serial
Out:   serial
Err:   serial
Net:   FEC1
Error: FEC1 address not set.

Normal Boot
Hit any key to stop autoboot:  0
=> mmc part

Partition Map for MMC device 0  --   Partition Type: DOS

Part    Start Sector    Num Sectors     UUID            Type
  1     2048            204800          8bb1460b-01     0e Boot
  2     206848          772096          8bb1460b-02     83
=> fatls mmc 0:1 boot
            ./
            ../
  5583352   zimage
    36274   my-i6ull.dtb

2 file(s), 2 dir(s)

=> fatload mmc 0:1 83000000 boot/my-i6ull.dtb
reading boot/my-i6ull.dtb
36274 bytes read in 22 ms (1.6 MiB/s)
=>
=> fatload mmc 0:1 80800000 boot/zImage
reading boot/zImage
Error reading cluster
** Unable to read file boot/zImage **
=>
=> fatload mmc 0:1 80800000 boot/zImage
** Can't read partition table on 0:0 **
** Invalid partition 1 **
=>
=>

后来我重新使用正点原子提供的nand和emmc的配置文件对UBoot进行编译（刚开始我一直用的是nand中的UBoot），然后调整boot到卡启动模式，这个问题仍然存在。我更换过使用的SD卡，仍无法解决。我不得不怀疑是否是厂家在修改UBoot的时候误操作了什么地方，接着我又使用nxp的uboot-imx-rel_imx_4.1.15_2.1.0_ga.tar.bz2源码包，使用mx6ull_14x14_evk_defconfig配置文件进行编译。我想大厂的总该没问题了吧！可惜的是，这个问题仍然存在。。。看来官方提供的UBoot可能真的有些bug

各种抓狂之下去UBoot的分ftp站点重新下载了一个版本，第一次下的是u-boot-2016.03.tar.bz2，结果却发现该版本只合并到mx6ul，重新下了u-boot-2017.03.tar.bz2，发现支持到了mx6ull，编译的时候提示我：Your dtc is too old, please upgrade to dtc 1.4 or newer ，执行：apt-get install device-tree-compiler 后再次使用mx6ull_14x14_evk_defconfig配置进行编译：

  ... 省略 ...
  DTC     arch/arm/dts/imx6dl-icore.dtb
  DTC     arch/arm/dts/imx6dl-icore-rqs.dtb
  DTC     arch/arm/dts/imx6q-icore.dtb
  DTC     arch/arm/dts/imx6q-icore-rqs.dtb
  DTC     arch/arm/dts/imx6sx-sabreauto.dtb
  DTC     arch/arm/dts/imx6ul-geam-kit.dtb
  SHIPPED dts/dt.dtb
  CAT     u-boot-dtb.bin
  CFGS    board/freescale/mx6ullevk/imximage.cfg.cfgtmp
  MKIMAGE u-boot-dtb.imx
  OBJCOPY u-boot.srec
  COPY    u-boot.bin
  SYM     u-boot.sym
  COPY    u-boot.dtb
  CFGCHK  u-boot.cfg
cat: u-boot.cfg: No such file or directory
root@hope-VirtualBox:/home/hope/work/uboot/u-boot-2017.03# ls u-boot*
u-boot              u-boot.dtb      u-boot-dtb.imx.log  u-boot-nodtb.bin
u-boot.bin          u-boot-dtb.bin  u-boot.lds          u-boot.srec
u-boot.cfg.configs  u-boot-dtb.imx  u-boot.map          u-boot.sym

烧写测试：

U-Boot 2017.03 (Aug 13 2020 - 10:05:02 +0800)

CPU:   Freescale i.MX6ULL rev1.1 69 MHz (running at 396 MHz)
CPU:   Industrial temperature grade (-40C to 105C) at 45C
Reset cause: WDOG
Model: Freescale i.MX6 ULL 14x14 EVK Board
Board: MX6ULL 14x14 EVK
DRAM:  512 MiB
MMC:   FSL_SDHC: 0, FSL_SDHC: 1
*** Warning - bad CRC, using default environment

In:    serial
Out:   serial
Err:   serial
Net:   CPU Net Initialization Failed
No ethernet found.
Hit any key to stop autoboot:  0
=> fatload mmc 0:1 80800000 boot/zImage
reading boot/zImage
5583352 bytes read in 346 ms (15.4 MiB/s)
=> fatload mmc 0:1 83000000 boot/my-i6ull.dtb
reading boot/my-i6ull.dtb
36274 bytes read in 23 ms (1.5 MiB/s)
=>

这下终于美滋滋了~~~~~~~load命令和fatload命令屡试不爽！kernel也能正常启动

老实说，起初我怀疑是mmc驱动有问题，但一看UBoot是能正确识别到sd卡的并且fatls命令输出的结果也正确，这意味着不太可能是驱动的问题。难不成是文件系统有bug？？？具体原因我还没来得及去细究，今天先记录下这个问题，等有时间的时候再去看看这令我抓狂的虫子到底在哪！有知道的朋友还望赐教~~