Re: quik kernel size limit

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Mon, 2003-10-13 at 22:34, Mich Lanners wrote:
> Hi all,
> 
> Recently it was discussed here whether quik has a limit on kernel size.
> 
> Well, while playing with 2.6 kernels I found out: yes, quik _does_ have
> a limit on kernel size. It is exactly 3981312 bytes. In fact, quik
> allocates a fixed-size buffer in which the kernel is loaded, and that
> buffer is from 0x14000 to SECOND_BASE (second/main.c), and SECOND_BASE
> is 0x3e0000 (include/layout.h).

And you can't extend it as those oldworld OFs love to have things
of their own between 0x3e0000 and 0x500000. What I did to 'fix' coffboot
(but that means I bumped the minimal mem requirement to 16Mb) was to
load the kernel at 0x800000 instead. That gives me 8Mb for 8Mb to 16Mb,
though with quik, you can probably load it a bit lower than that
(depends where quik itself is linked). For coffboot, I needed the room
between 5Mb and 8Mb for the compressed image. Actually, I even bumped
that to 5Mb to 9Mb and from 9Mb to 16Mb for the kernel+ramdisk

Note also that when doing that, you also want to:

 - Update the BAT mapping code to map 16Mb instead of just 8
 - Use an OF map() call to create a 1:1 mapping in the OF own
   tables (not that the MAP may be useless thanks to that mapping,
   but we keep it for efficiency on oldworld). Without this map()
   call, you'll end up with the OF "translate" call failing in the
   kernel entry.

Ben.