[U-Boot] platform configuration

[Andrew Dyer]

On Thu, Sep 25, 2008 at 3:04 AM, Roman Mashak <romez777 at gmail.com> wrote:
> Hello
>
> Reading u-boot's README paper and trying to figure out a few aspects:
>
> (1) as I know the bootloader sets up memory area for argument passing,
> initializes it with data structures and fill up with the values. Is
> this the structure defined in $(UBOOT)/include/asm-arm/global_data.h,
> named 'global_data' ?
>
> (2) this question is a consequence of the first.
> 'struct bd_info' from $(UBOOT)/include/asm-arm/u-boot.h is a structure
> holding board's specific information, am I right?
>
> How is the address of boot parameters determined
> ("bd->bi_boot_params"). If speaking about Linux, it is defined in
> $(LINUX)/arch/arm/mach-xxx/Makefile.boot -- but how is it defined to
> be what it is?
>
> (3) can't yet figure out how CONFIG_BOOTARGS  is pulled in. Somwhow it
> should get into board's information structure?
>
> Thanks in advance for comments.
>

Many (most?) ARM kernel ports use a format called ATAGS to pass
information to the linux kernel at startup.  CONFIG_CMDLINE_TAG tells
u-boot to include ATAGS support, there are a variety of tags that can
be included with different CONFIG options.  Have a look at
lib_arm/bootm.c - where the kernel actually gets called is in line
125, like so:
theKernel(0, machid, bd->bi_boot_params)

where the arguments get put into registers r0, r1, r2 and are 0, the
machine ID, and a pointer to the ATAGS structure respectively.

http://www.arm.linux.org.uk/developer/booting.php#5 also has some more
info about the tags & booting

-- 
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 The parts of a computer system that can be kicked.