What is the best way to replace kernel when developping?

[rbuchmann77]

Hello,

I'm currently trying some set of kernel configurations and the only way to test it is to build & flash the full image.

I'm using mender. So it's faster than using doflash.sh.
However, yocto takes a lot of time to build the full image (not only the kernel) and the mender bundle.

I'm looking for the faster approach.

The following command is nice to understand the layout:
lsblk --f --bytes --output NAME,FSTYPE,MOUNTPOINT,PARTLABEL,SIZE,STATE,TYPE
I guess boot.img is in the partlabel "kernel" or "kernel_b", given the current slot.
Unfortunately, I failed to read/write kernel image from/to those partitions.

[madisongh]

There's no single good answer; there are different options, and which one you might choose depends on the specific Jetson model you're using, your other hardware, which L4T version you're using, and your preferred workflow.

One approach is to use an extlinux.conf setup, and just copy the kernel and device tree into /boot/ to test. This should work with L4T R32.6.x/R32.7.x across all of the Jetsons. (For Xavier platforms, you have to include cboot-extlinux in your image - see the notes here.) You may have to hand-edit the extlinux.conf file with an FDT line to force cboot or U-boot (depending on the target Jetson) to replace the device tree loaded at boot time with the copy associated with the kernel you're testing.

Another approach is to build a BUP payload with your test kernel and device tree and use tegra-bootloader-update to install that for testing. The kernel-bup-payload (for cboot platforms) and uboot-bup-payload (for U-boot platforms) generates a kernel_only.bup-payload that you can use for this. For the TX2 and Xavier, you have to keep track of which boot slot you've booted from and tell tegra-bootloader-update to update the kernel/dtb in that slot.

You can also flash just the kernel and DTB to boot partitions via USB, if your builds are not using the extlinux.conf kernel loading mechanism. Exactly what commands you need to do this will vary by Jetson target and by L4T version, but the basic approach is to use the -c option to the doflash.sh script to have tegraflash.py run specific flashing commands. If you search around the discussions area here for doflash.sh, you'll see some examples.

[leadercxn]

Hi @madisongh , I added cboot-extlinux and UBOOT_EXTLINUX_FDT in my yocto recipes

and manually modified /boot/extlinux/extlinux.conf and added the dtb file into my system,

but I did not find that the system called the file in the system startup log.

HW：Xavier NX
Branch: kirkstone-l4t-r32.7.x

[leadercxn]

In fact, I wanted to debug the device tree by replacing the dtb files, rather than burning the entire system, to make the development phase more efficient.

[leadercxn]

Oh, I should set these variable UBOOT_EXTLINUX_FDTDIR and UBOOT_EXTLINUX_FDT in cboot-extlinux-config.bbclass file.