Hello Mats,

On Thu, 2019-12-12 at 16:49 +0100, Mats Jansson wrote:

Hi,

I want to set up for an upgrade of our embedded system, using a special kernel for the upgrade. The standard will be to load the system from mtd3 (kernel), mtd4 (devicetree) and mtd5 (rootfs).

When an update is to take place I want to run the upgrade system from mtd0.

So basically I need to have some sort of telling U-boot that it should launch the upgrade system instead of the standard system.

Any ideas how I set this up? How to tell u-boot? How to get u-boot to boot from another partition based on a condition like that?

The easiest way to instruct U-Boot to boot a different system (in your case from a different partition) is to set a U-Boot environment variable from within Linux. Your boot-script in U-Boot should then check this environment variable and boot into your upgrade system.

To do this, there are the envtools [1] found in the U-Boot sources in `tools/env/`. Alternatively, you can use libubootenv [2] which is a project separate from U-Boot but which archieves the same thing.

Both those packages contain an `fw_setenv` tool which you can use just like `setenv` on the U-Boot command-line. The only difference is that `fw_setenv` automatically saves the environment so you don't need any `saveenv` like command afterwards.

To make those tools work, you'll need to create a configuration file `/etc/fw_env.config` which tells the tool where the U-Boot environment is located. The example config [3] contains everything you need to know.

Regards Mats mailto:matsmanhav@tele2.se

Hope this helps!

[1]: https://gitlab.denx.de/u-boot/u-boot/tree/master/tools/env [2]: https://github.com/sbabic/libubootenv [3]: https://gitlab.denx.de/u-boot/u-boot/blob/master/tools/env/fw_env.config