Customize U-boot script to modify u-boot process

Question

I am trying to customize the boot script which is used to boot my STM32MP157 Avenger96 board. I want to include some u-boot variables and alter the boot process.Current boot script:if test -n "${distro_bootpart}"; then
 setenv partition "${distro_bootpart}"
else
 setenv partition "${bootpart}"
fi
 
if test ! -e ${devtype} ${devnum}:${partition} boot/fitImage; then
 echo "This boot medium does not contain a suitable fitImage file for this system."
 echo "devtype=${devtype} devnum=${devnum} partition=${partition} loadaddr=${loadaddr}"
 echo "Aborting boot process."
 exit 1
fi
 
part uuid ${devtype} ${devnum}:${partition} uuid
 
# Some STM32MP1-based systems do not encode the baudrate in the console variable
if test "${console}" = "ttySTM0" && test -n "${baudrate}"; then
 setenv console "${console},${baudrate}"
fi
 
if test -n "${console}"; then
 setenv bootargs "${bootargs} console=${console}"
fi
 
#New variables I want to include bootlimit rootfspart
setenv bootlimit 5
setenv rootfspart 4
 
setenv bootargs "${bootargs} root=PARTUUID=${uuid} rw rootwait consoleblank=0"
 
#Pass bootargs like this
setenv bootargs "${bootargs} root=/dev/mmcblk0p${rootfspart} rdinit=/bin/kinit rw single\0"
 
load ${devtype} ${devnum}:${partition} ${loadaddr} boot/fitImage
if test $? != 0 ; then
 echo "Failed to load fitImage file for this system from boot medium."
 echo "devtype=${devtype} devnum=${devnum} partition=${partition} loadaddr=${loadaddr}"
 echo "Aborting boot process."
 exit 2
fi
 
# A custom script exists to load DTOs
if test -n "${loaddtoscustom}" ; then
 # Pull DTOs from fitImage and manually apply them to base DT
 if test -n "${loaddtos}" ; then
 # Matches UBOOT_DTB_LOADADDRESS in OE layer machine config
 setexpr loadaddrdtb 0xcff00000
 # Matches UBOOT_DTBO_LOADADDRESS in OE layer machine config
 setexpr loadaddrdtbo 0xcff80000
 
 setexpr loaddtossep gsub '#conf' ' fdt' "${loaddtos}"
 setexpr loaddtb 1
 
 for i in ${loaddtossep} ; do
 if test ${loaddtb} = 1 ; then
 echo "Using base DT ${i}"
 imxtract ${loadaddr} ${i} ${loadaddrdtb} ;
 fdt addr ${loadaddrdtb}
 fdt resize
 setenv loaddtb 0
 else
 echo "Applying DTO ${i}"
 imxtract ${loadaddr} ${i} ${loadaddrdtbo} ;
 fdt apply ${loadaddrdtbo}
 fi
 done
 
 setenv loaddtb
 setenv loaddtossep
 setenv loadaddrdtbo
 setenv loadaddrdtb
 fi
 
 # Run the custom DTO loader script
 #
 # In case 'loaddtos' variable is set, then the 'fdt' command is already
 # configured to point to a DT, on top of which all the DTOs present in
 # the fitImage and selected by the 'loaddtos' are applied. Hence, the
 # user is now free to apply any additional custom DTOs loaded from any
 # other source.
 #
 # In case 'loaddtos' variable is not set, the 'loaddtoscustom' script
 # must configure the 'fdt' command to point to the custom DT.
 run loaddtoscustom
 if test -z "${bootm_args}" ; then
 setenv bootm_args "${loadaddr} - ${fdtaddr}"
 fi
else
 setenv bootm_args "${loadaddr}${loaddtos}"
fi
 
echo "Booting the Linux kernel..." \
&& bootm ${bootm_args}Now I want to add bootlimit and rootfspart to above script and also to pass bootargsas setenv bootargs "${bootargs} root=/dev/mmcblk0p${rootfspart} rdinit=/bin/kinit rw single\0".The config file is in include/configs/dh_stm32mp1.h#ifndef __CONFIG_DH_STM32MP1_H__
#define __CONFIG_DH_STM32MP1_H__
 
#include <configs/stm32mp1.h>
 
#define CONFIG_BOOTCOUNT_LIMIT
#define CONFIG_BOOTCOUNT_ENV
 
#define CONFIG_SPL_TARGET "u-boot.itb"
#undef STM32MP_BOOTCMD
#define STM32MP_BOOTCMD "bootcmd_stm32mp=" \
 "if run load_bootenv; then run importbootenv;fi;" \
 "echo \"Boot over ${boot_device}${boot_instance}!\";" \
 "if test ${boot_device} = serial || test ${boot_device} = usb;" \
 "then stm32prog ${boot_device} ${boot_instance}; " \
 "else " \
 "run env_check;" \
 "if test ${boot_device} = mmc;" \
 "then env set boot_targets \"mmc${boot_instance}\"; fi;" \
 "if test ${boot_device} = nand ||" \
 " test ${boot_device} = spi-nand ;" \
 "then env set boot_targets ubifs0; fi;" \
 "run distro_bootcmd;" \
 "fi;\0"
 
#undef CONFIG_EXTRA_ENV_SETTINGS
#define CONFIG_EXTRA_ENV_SETTINGS \
 "bootdelay=1\0" \
 "bootlimit=5\0" \
 "rootfspart=4\0" \
 "bootargs=root=/dev/mmcblk0p${rootfspart} rdinit=/bin/kinit rw single\0" \
 "kernel_addr_r=0xc2000000\0" \
 "fdt_addr_r=0xc4000000\0" \
 "scriptaddr=0xc4100000\0" \
 "pxefile_addr_r=0xc4200000\0" \
 "splashimage=0xc4300000\0" \
 "ramdisk_addr_r=0xc4400000\0" \
 /*"altbootcmd=run bootcmd\0" \ */
 "env_default=1\0" \
 "env_check=if test $env_default -eq 1;"\
 " then env set env_default 0;env save;fi\0" \
 STM32MP_BOOTCMD \
 BOOTENV \
 "altbootcmd=" \
 " echo Rollback to previous RootFs; " \
 " if test ${rootfspart} = 4; " \
 " then setenv rootfspart 5; " \
 " else " \
 " setenv rootfspart 4; " \
 " fi; setenv bootcount 0; saveenv; " \
 " bootcmd\0" \
 "boot_net_usb_start=true\0" \
 "usb_pgood_delay=1000\0" \
 "update_sf=" /* Erase SPI NOR and install U-Boot from SD */ \
 "setexpr loadaddr1 ${loadaddr} + 0x1000000 && " \
 "load mmc 0:4 ${loadaddr1} /boot/u-boot-spl.stm32 && " \
 "env set filesize1 ${filesize} && " \
 "load mmc 0:4 ${loadaddr} /boot/u-boot.itb && " \
 "sf probe && sf erase 0 0x200000 && " \
 "sf update ${loadaddr1} 0 ${filesize1} && " \
 "sf update ${loadaddr1} 0x40000 ${filesize1} && " \
 "sf update ${loadaddr} 0x80000 ${filesize} && " \
 "env set filesize1 && env set loadaddr1\0" \
 "load_bootenv="\
 "usb stop; usb start; if load usb ${usbdev}:${usbpart} ${loadaddr} DHupdate.ini;" \
 "then echo \"--> Update: found DHupdate.ini (${filesize} bytes)\"; fi;\0"\
 "importbootenv=echo Importing environment from DHupdate.ini...; env import -t ${loadaddr} ${filesize}\0"\
 "usbdev=0\0"\
 "usbpart=1\0"
#endifI have also included bootlimit and rootfspart and passed bootargs in above file. My question is:Do I need to again define these variables in the config file?Also, I want to use altbootcmd like above. Is this correct? Will the above modifications work?After these changes I bitbaked the u-boot recipe and bitbaked the image recipe and copied the file to SD card and booted from it. But when I do fw_printenv rootfspart or fw_printenv bootlimit I cannot see the set values or it returned empty.And also how are the variables like ${distro_bootpart} and ${devtype} set in boot script? From where are these variables accessed?Can anyone please let me know what am I doing wrong and how to make this work?Your help will be much appreciated.Thanks in advance.P.S: I am new to U-boot and learning to use it. I am using Yocto as build system with Ubuntu 20.04. Please let me know if you need any further info.

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