[U-Boot] Debugging why my kernel won't start

[Albert ARIBAUD <albert.aribaud@free.fr>]

Le 17/08/2010 12:21, Rogan Dawes a ?crit :
> On 2010/08/17 12:10 PM, Albert ARIBAUD wrote:
>> (quick note to Wolfgang: yes, there is RAM at 0x00008000 on these
>> machines. All orion5x based machines have RAM start at 0, and u-boot
>> makes sure SDRAM is set up this way)
>>
>> Rogan,
>>
>> You cannot tell from your log output that memmove never completes. It
>> could as well be the kernel not outputting to the console, or failing to
>> start at all even though the move was ok.
>
> Actually, I can tell that the memmove never completes (or if it does, it
> alters the code flow in the process):
>
>>> So I changed memmove_wd to use the watchdog style of memmove'ing, in
>>> small chunks to try to track down where the problem arises. I used 1kB
>>> chunks, and got:
>>>
>>> Moving 1024 of 611612 bytes from ff8f6840 to 000de800
>>> Moving 1024 of 610588 bytes from ff8f6c40 to 000dec00
>>> Moving 1024 of 609564 bytes from ff8f7040 to 000df000
>>>
>>> before it finally hung.
>
> I had a debug statement in the loop, printing out the above at each
> iteration. Since it never completed the loop, copying/moving the entire
> kernel (609564 bytes remaining), I think it is safe to assume that it
> never got to the point of trying to boot the kernel.

Sorry, I'd missed that one.

> Additionally, just doing a cp with the above parameters also hangs.
>
> Based on what Wolfgang has said, perhaps the address space registers are
> set up differently in the vendor u-boot to what the current mainline is
> doing. I'll check that next, I think.

> I'm just struggling to understand how the last command that I executed
> ended up in the memory where I was trying to copy the kernel to. That
> suggests that U-boot is actively using that memory for some reason, and
> copying the kernel image over the top of it seems like a very good way
> to cause u-boot to stop behaving consistently, and hang.

I do think you're overwriting u-boot with the kernel. What location does 
your u-boot load at? What location is the manufacturer's u-boot supposed 
to be loading at? See their TEXT_BASE in the board config file (or link 
file maybe).

FYI, in my u-boot edminiv2 support code, I had issues with big kernels, 
so I decided to move u-boot's final location as high in RAM as by board 
allows, so that it never will be overwritten by Linux (unless I load a 
63+ MB kernel, that is :) )

> Thanks anyway.
>
> Rogan

You're welcome.

Amicalement,
-- 
Albert.