[U-Boot-Users] ARM, bootm and bootargs

[Friedrich, Lars]

Curt Brune wrote something slightly offtopic and may the gods forgive me
for answering here, but hopefully this answer will prevent further
similiar questions:

> I'm trying to pass command line arguments from u-boot to the kernel
> for an ARM-based board.  Following the README I'm setting the
> environment variable "bootargs" to the command line I want and booting
> with the "bootm" command.
> 
> When the kernel boots it prints it's command line, which is still the
> default command line.  I was expecting to the see the command line I
> stored in the "bootargs" variable.
> 
> I poked around in u-boot/lib_arm/armlinux.c and it looks like I needed
> to have CONFIG_CMDLINE_TAG defined in my config, which I did.
> 
> Is there anything else I need to do?  Something I'm missing?

Assuming you are trying to boot uClinux and the 2.4.x kernel, then
you need to modify uClinux-dist/linux-2.4.x/arch/armnommu/kernel/arch.c

There you'll find MACHINE_START(NETARM, "NET+ARM). Within the MACHINE_START
and MACHINE_END sequence you need to add BOOT_PARAMS(<value>) (no semicolon at the
end please). And the value you have to enter is whatever is set in
file: u-boot/board/xxxx(modnet50?)/xxxx(modnet50?).c
function: int board_init (void)
variable: gd->bd->bi_boot_params=<value>

If compiled with bdinfo support, you can also type bdinfo at the u-boot command prompt.
boot_params is the currently set <value>.

The default value for the modnet50 board is f.e. 0x800. You just have to make sure
that it is indeed a valid ram address for your custom board (and that of course it
doesn't get overwritten when you boot linux).

Best regards,
Lars Friedrich

--