[U-Boot-Users] OS dependencies on the bootloader

[U-Boot-Users] OS dependencies on the bootloader

[Andrew Wozniak]

Hello everyone,

A general bootloader question: How much hardware initialization should a 
bootloader perform for the target OS?

I see a minimal memory controller setup to allow subsequent loading of 
an OS image. ECC might also be setup but all remaining resources would 
typically be setup by the OS.

Although I haven't tried booting Linux (we boot the vxworks bootrom), 
does an embedded Linux make any assumptions about what the bootloader 
initializes?

Thank you and best regards, Andy

[U-Boot-Users] OS dependencies on the bootloader

[Wolfgang Denk]

In message <43BC4A51.9050203@mc.com> you wrote:
> 
> A general bootloader question: How much hardware initialization should a 
> bootloader perform for the target OS?

As little as possible, as much as necessary.

> I see a minimal memory controller setup to allow subsequent loading of 
> an OS image. ECC might also be setup but all remaining resources would 
> typically be setup by the OS.

Right.

> Although I haven't tried booting Linux (we boot the vxworks bootrom), 
> does an embedded Linux make any assumptions about what the bootloader 
> initializes?

Yes. Depending on architecture and kernel versions certain parameters
(ATAGs, bd_info structure, OF tree, whatever) have to be  initialized
and passed to the kernel.

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Digital computers are themselves more complex than most things people
build: They have very large numbers of states. This makes conceiving,
describing, and testing them hard. Software systems  have  orders-of-
magnitude more states than computers do.           - Fred Brooks, Jr.