How to boot on a custom Linux built with Buildroot?

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1

I try to figure out how to create and boot on a SD card with Buildroot I first followed this tutorial to create a SD card with an Ubuntu rootfs to see if it works : https://eewiki.net/display/linuxonarm/BeagleBone+Blue
It did.

Then I tried to build a full image with Buildroot using the beaglebone_defconfig configuration file. The result is completely different. The first tutorial gives me a single partition with U-Boot written first and the kernel and the DTB files in a boot/ subdirectory. and the build from Buildroot gives me 2 partitions “boot” and “rootfs” with the bootloader, the kernel and the DTB file in the first one and the rootfs in the second one. Unfortunately that didn’t work.

I edited the beaglebone board configuration to add the am335x-boneblue.dts source file and the U-boot patches provided in the first tutorial without success. In the configuration file, the Kernel sources are fetched from a TI repository. Why the official BeagleBone linux kernel repository on GitHub isn’t used instead? I tried with the official kernel without success. Where could I find the conditions to make the BeagleBone Blue boot on my SD card? The BeagleBone Black and Blue seems to be based on the same hardware but why are the SD card partitions so different?

2

Buildroot uses one of TI's 4.4.x based kernel's:

https://github.com/buildroot/buildroot/blob/master/configs/beaglebone_defconfig

I pushed the blue mainline in v4.13.x...

Since i maintain the beagleboard kernel builds, my v4.4.x/v4.9.x
kernels got backports to support the blue..

So if you want buildroot support for the Blue, you'll have to do some
kernel patching..

Buildroot uses the old fat=boot, ext=rootfs partition setup. We moved
to a single partition a few years back, as users were soft-bricking
their boards by deleting the bootloader files.

Regards,

3

OK so what’s the official kernel sources for the Blue?

I tried different sources, the one provided by Buildroot and this one : https://github.com/beagleboard/linux.
I’ve seen that you use an other more repository you host on GitHub that you patch with dozen of patches from an other repository you host to build an Debian/Ubuntu based distro.
Is there any “kernel only” repository with working source for the Blue or a list of patches needed to make it works?

If the partitioning changed, I’ll just have to learn the genimage config file syntax to make it works. No fear.

Thanks,
Cyril

4

For the Blue:

1: Pure Mainline:

2:
https://github.com/beagleboard/linux

All these branches:

4.4 4.4-rt
4.9 4.9-rt
4.14 4.14-rt

3: lots more..

Regards,

6

Is there any BB blue kernel defconfig file you recommand to use?
What patches are needed?

Best regards,
Cyril F.

7

It’s not part of Buildroot.

8

https://github.com/beagleboard/linux

Pick any of these branches:

4.4
4.4-rt
4.9
4.9-rt
4.14
4.14-rt

and use the "bb.org_defconfig"

Regards,

9

You said that I must patch the kernel. Is that needed with this?
Can I use the RoboticsCape library to program the BB blue? Thank you.

Regards,
Cyril F.

10

Correct, "you" must patch the kernel if you use someone's else's Kernel tree..

However since "we" support the Blue at BeagleBoard.org, our "tree"
already includes all the patches you need.

For the blue, the "4.4 or 4.4-rt" branches on

https://github.com/beagleboard/linux

work best with the RoboticsCape library.

Regards,