Uboot and uClinux

Altera_Forum · ‎04-21-2005

Hello all,

I wish to make my uboot (loaded in flash and started at each boot) launching my uClinux kernel at startup. For the moment all I succeeded to do is starting a compressed kernel image in RAM (which reboot processor once "decompressing kernel.....OK" is done...).

I use : / mkimage -A Nios2 -O Linux -T kernel -C gzip -a 0 -e 0 -n "uClinux kernel" -d linux.bin.gz uImage

I download the image via "loadb" command. As result I get this (after a "iminfo" command):

## Checking Image at 02000000 ...
   Image Name:   linux kernel image
   Image Type:   Unknown Architecture Linux Kernel Image (gzip compressed)
   Data Size:    772947 Bytes = 754.8 kB
   Load Address: 00000000
   Entry Point:  00000000
   Verifying Checksum ... OK

First question : When generating the image for uboot, what are the correct values for

     
Load Address: ...
Entry Point:  ...

?

I tried 0x0 / 0X0. But my kernel still rebooting processor after "decompressing kernel.....OK".

Next, can I upload my romfs filesystem as I did for the kernel ? I tried but get "out of limits" each time I try to download the fs image into ram, so I couldn't investigate further more at this time.

I've read DULG > Faq and others 'Kernel Hangs After Decompressing' topics but couldnt find useful help (as it seems related to a particular architecture).

Thanks for help,

Max.

Altera_Forum · ‎04-21-2005

Hi Max,

> mkimage -A Nios2 ...

The parameter should be "nios2" (case is significant). For most architectures, the

-A option is the same as the "arch" part of binutils (e.g. "powerpc", "arm", etc).

This will eliminate the "Unknown Architecture" report.

> When generating the image for uboot, what are the correct values for

> Load Address: ...

> Entry Point: ...

The load address is the address where the image data is copied (after decompressing

if the image is compressed). The entry point is the target __address__ of a jump -- it's

where execution begins. For uClinux, this is currently at __offset__ 0. For some

architectures, the entry point offset is not zero (e.g. arm, powerpc) -- so it's a standard

option for mkimage.

Depending on your hardware, what you are trying to do, and the actual code that

you're booting, the load address may be different. For uClinux, the load address really

doesn't matter since the kernel will relocate itself to the correct run-time address

(although you must be careful not to 'overlap upward' since the Nios-II uClinux

startup code won't handle this situation correctly. A downward overlap -- copying

from a higher address to a lower address -- won't be a problem).

Chances are that your kernel was linked to the start of your SDRAM, which in the

1.1 'standard' config example begins at 0100_0000. So you can just set your load

address and entry point to that value:

$ mkimage -A nios2 -O linux -T kernel -C gzip -a 0x01000000 -e 0x01000000 ....

And don't worry about trashing the exception trampoline ... u-boot disables

interrupts prior to the copy/decompress.

> I tried 0x0 / 0X0. But my kernel still rebooting processor after "decompressing kernel.....OK".

Yep, bootm is trying to decompress into flash ... then it jumps to address 0.

> can I upload my romfs filesystem as I did for the kernel ?

Yes. I believe you can upload it directly into flash (after erasing it), but I never

use that feature ... so I don't know how well it works ... seems a bit dangerous

to me ;-) You can always use the nios2-flash-programmer ... really a very fine

job by Altera on this ... at least from the command line ;-)

> I tried but get "out of limits" each time I try to download the fs

> image into ram, so I couldn't investigate further more at this time.

If u-boot is reporting the "out of limits", try uploading the image into SDRAM

rather than the SRAM. i.e. loadb to address 0100_0100 -- don't loadb over

the exception trampoline at 0100_0020 ;-)

As an aside, you might want to consider using cramfs ... for a read-only fs,

you'll get a much smaller fs image size ... and all the nice side-effects (like

upload time, etc).

Regards,

--Scott

Altera_Forum · ‎04-22-2005

Hi Scott,

<div class='quotetop'>QUOTE </div>

--- Quote Start ---

Chances are that your kernel was linked to the start of your SDRAM, which in the

1.1 'standard' config example begins at 0100_0000. So you can just set your load

address and entry point to that value:

$ mkimage -A nios2 -O linux -T kernel -C gzip -a 0x01000000 -e 0x01000000 ....[/b]

--- Quote End ---

Looks like it was the problem. Works perfectly now (even if I still get "unknow architecture" but it doesn't matter obviously). Your are just great http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/cool.gif

Thanks for all the details and adivces, I'll follow them up.

Regards,

Max