Re: [U-Boot] Chain loading an u-boot from an u-boot

Hi Helmut,

On 10/02/2014 12:11, Helmut Raiger wrote:

So the idea was:

• use a small u-boot (<128kB) in the first PEB of the NAND (written with

1bit HW-ECC) that supports 4bit BCH

• let it load a second u-boot (<512kB) from the next 4 PEBs (written

with 4bit BCH)

• jump to the second u-boot and load the kernel from an UBI volume using

1bit HW-ECC again

I understand the first two points, but why do you store the kernel again with 1bit HW-ECC ? The second U-Boot is able to check with 4bit BCH and your NAND requires 4bit.

I did all that and it seemed to work just fine, but jumping to the second u-boot almost always crashes the system. In detail we do:

• romboot loads the SPL (2kb)
• SPL loads the first u-boot stage (which relocates and runs nicely)
• the first u-boot 'boots' the second u-boot by loading it from the NAND
• the second u-boot is loaded to the link address minus 2kB (for SPL)
• this is the same for the first and the second u-boot (link address

0x87e00000 - 0x800 = 0x87dff800)

• it jumps to 0x87e00000 omitting the SPL for the second u-boot
• the second u-boot should relocated itself again

The second u-boot is verified in RAM with crc32 and it is valid.

I've tested many configuration and found, that it only works if both u-boots are identical:

• different builds of the same code work (different build date, but same

code)

I agree with Andreas' analyses. It seems that the second u-boot overwrites your running U-Boot and only if they are identical you have no problem, that means that you are not changing the running code.

Regards, Stefano Babic