Configure U-boot using Yocto - embedded-linux

Question

I am new to U-boot and trying to modify some configuration in the U-boot. I am using STM32MP1 based Avenger96 boiard with Yocto Project and U-boot bootloader. Now I want to modify some U-boot variables like bootcount and bootlimit. For example I want to set bootlimit variable to 4 and if limit is reached, u-boot should run the altbootcmd instead of usual bootcmd.
To make this work I need to edit CONFIG_EXTRA_ENV_SETTINGS statement in the u-boot sources.
But I am not sure how to find the location of this file to be modified.
After spending some time to know about boot process to bring up the board I got to know that it uses boot.cmd file. It contains:
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=${console}"
fi
setenv bootargs "${bootargs} root=PARTUUID=${uuid} rw rootwait consoleblank=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 ${loadaddrdtbo}
fi
done
setenv loaddtb
setenv loaddtossep
setenv loadaddrdtbo
setenv loadaddrdtb
fi
run loaddtoscustom
if test -z "${bootm_args}" ; then
setenv bootm_args "${loadaddr} - ${fdtaddr}"
fi
else
setenv bootm_args "${loadaddr}${loaddtos}"
fi
echo "Booting the Linux kernel..." \
&& bootm ${bootm_args}
Now I want to add something like
bootlimit=5\0" \
rootfspart=4\0" \
bootargs=root=/dev/mmcblk0p${rootfspart} rdinit=/bin/kinit rw single\0" \
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" \
Can anyone please let me know how can I achieve this? Do I need to create a config fragment to the u-boot recipe or do I need to add patch file? Or is there a better way to implement?
Please let me know if further details are required.
Your help will be much appreciated.
Thanks in advance.