Minimal boot loader for loading uBoot

[kevin_chaves]

So I'm looking into how hard it will be to write our own little boot loader. Its similar to what linaro's spi to sd loader but we wanted to be able to switch to a back up sd card with a uboot on it. We are thinking about doing this because they want field update uboot safely.

With that said, I'm wondering what other peoples thoughts on this are. I already proposed the "don't do that" solution and just said it would be easier to make sure uboot isn't going to need an update. Also what is uboot responsible for configuring and initializing at boot that isn't on the SOC?

[OtavioSalvador · Accepted solution]

Please read:

https://community.freescale.com/message/314188#314188

[kevin_chaves]

So I can build uboot in a minimal way thats like the UBL that omaps have. Interesting...

Any really good documentation on the SPL?

[OtavioSalvador]

The best documentation has not yet been merged into U-Boot mainline but it is in the review process; current patchset for the documentation is at:

Gmane Loom

[kevin_chaves]

I'm actually going to be using it the way its intended. I think i'm a little confused, I want to load uboot with this but possibly from a different source holding down a couple of keys.

Is SPL supported normally on i.MX6?

Does the patch contain support for the i.mx6 for the normal and falcon mode?

[OtavioSalvador]

You can do that; check the SabreLITE environment in U-Boot mainline; you can use same idea to process the keys and change the environment during runtime.

[kevin_chaves]

Awesome thanks,

Do you know any good sources on uboot in general, we are currently switching from wince with ubl/eboot setup so I feel like i'm in over my head. I still really don't even understand how configuring uboot works and how to build the spl vs normal uboot.

[OtavioSalvador]

Well, the source code ;-) Sorry.

Do you intend to use WinCE being load by U-Boot or to move to Linux?

[kevin_chaves]

Moved to linux, this is why i feel a bit in over my head, we threw everything out the window and started with a new kernel, dev environment, bootloader, hardware, source control... its awesome.

Is all the device init in the ./board/<board> . Since we are trying to solve problems we don't actually have yet they want to be able to update uboot safely if we forgot something. I feel like might actually be easier to strip it down and let the kernel initialize the device.

we are using an imx6, is it possible to just turn on the ram, load the kernel from an sd card with minimal initialization so we don't have to worry about "forgetting" something.

[OtavioSalvador]

When doing this huge change maybe a consulting would be good. You may take wrong routes sometimes.

For Linux please also take a look in Yocto as it will make your life easier than LTIB ;-)

Regards,

[kevin_chaves]

i love yocto, we started with yocto but we felt like we needed help so we got a seat with timesys. Their build system is just as awful as ltib.

[OtavioSalvador]

So we need to talk ;-)