u-boot environment preset for sdcard mirror

[#1]

In some cases, such as mass production or preparing a demo.

We need u-boot environment stored in demo sdcard mirror image. 

Here is a way:

HW:  i.MX8MP evk

SW:  LF_v5.15.52-2.1.0_images_IMX8MPEVK.zip

The idea is to use fw_setenv to set the sdcard mirror as the operation on a real emmc/sdcard.
Add test=ABCD in u-boot-initial-env for test purpose.
And use fw_printenv to check and use hexdump to double confirm it.
The uboot env is already written into sdcard mirror(imx-image-multimedia-imx8mpevk.wic).
All those operations are on the host x86/x64 PC.

 ./fw_setenv -c fw_env.config -f u-boot-initial-env
Environment WRONG, copy 0
Cannot read environment, using default

 ./fw_printenv -c fw_env.config
Environment OK, copy 0
 jh_root_dtb=imx8mp-evk-root.dtb
 loadbootscript=fatload mmc ${mmcdev}:${mmcpart} ${loadaddr} ${bsp_script};
 mmc_boot=if mmc dev ${devnum}; then devtype=mmc; run scan_dev_for_boot_part; fi
arch=arm
baudrate=115200
......
......
......
splashimage=0x50000000
test=ABCD
usb_boot=usb start; if usb dev ${devnum}; then devtype=usb; run scan_dev_for_boot_part; fi
vendor=freescale

 
hexdump -s 0x400000 -n 2000 -C imx-image-multimedia-imx8mpevk.wic
            
00400000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

hexdump -s 0x400000 -n 10000 -C imx-image-multimedia-imx8mpevk.wic
00400000  5f a4 9b 97 20 6a 68 5f  72 6f 6f 74 5f 64 74 62  |_... jh_root_dtb|
00400010  3d 69 6d 78 38 6d 70 2d  65 76 6b 2d 72 6f 6f 74  |=imx8mp-evk-root|
00400020  2e 64 74 62 00 20 6c 6f  61 64 62 6f 6f 74 73 63  |.dtb. loadbootsc|
00400030  72 69 70 74 3d 66 61 74  6c 6f 61 64 20 6d 6d 63  |ript=fatload mmc|
00400040  20 24 7b 6d 6d 63 64 65  76 7d 3a 24 7b 6d 6d 63  | ${mmcdev}:${mmc|
00400050  70 61 72 74 7d 20 24 7b  6c 6f 61 64 61 64 64 72  |part} ${loadaddr|
00400060  7d 20 24 7b 62 73 70 5f  73 63 72 69 70 74 7d 3b  |} ${bsp_script};|
00400070  00 20 6d 6d 63 5f 62 6f  6f 74 3d 69 66 20 6d 6d  |. mmc_boot=if mm|
......
......
......
00401390  76 3d 31 00 73 6f 63 3d  69 6d 78 38 6d 00 73 70  |v=1.soc=imx8m.sp|
004013a0  6c 61 73 68 69 6d 61 67  65 3d 30 78 35 30 30 30  |lashimage=0x5000|
004013b0  30 30 30 30 00 74 65 73  74 3d 41 42 43 44 00 75  |0000.test=ABCD.u|
004013c0  73 62 5f 62 6f 6f 74 3d  75 73 62 20 73 74 61 72  |sb_boot=usb star|
004013d0  74 3b 20 69 66 20 75 73  62 20 64 65 76 20 24 7b  |t; if usb dev ${|
004013e0  64 65 76 6e 75 6d 7d 3b  20 74 68 65 6e 20 64 65  |devnum}; then de|

flash the sdcard mirror into i.MX8MP evk board emmc to check

uuu -b emmc_all imx-boot-imx8mp-lpddr4-evk-sd.bin-flash_evk  imx-image-multimedia-imx8mpevk.wic

 The first time boot, the enviroment is already there.

 How to achieve that:

a. fw_setenv/fw_printenv:

https://github.com/sbabic/libubootenv.git

Note: Please do not use uboot fw_setenv/fw_printenv

Compile it on the host x86/x64 PC. It is used on host.

b. u-boot-initial-env

Under uboot, make u-boot-initial-env

Note: Yocto deploys u-boot-initial-env by default

c. fw_env.config 

imx-image-multimedia-imx8mpevk.wic 0x400000 0x4000

0x400000 0x4000 are from uboot-imx\configs\imx8mp_evk_defconfig

CONFIG_ENV_SIZE=0x4000
CONFIG_ENV_OFFSET=0x400000

Now, you can run 

./fw_setenv -c fw_env.config -f u-boot-initial-env