Early kernel hang with big DTB appended

[Sascha Hauer]

On Thu, Jan 03, 2013 at 04:55:00PM +0100, Tomasz Figa wrote:
> Hi,
> 
> I'm observing strange behavior when booting 3.8-rc1 and -rc2 with appended 
> DTB. The kernel hangs very early when the DTB is bigger than some 
> threshold somewhere around 24 KiB. With fullest possible low level UART 
> debugging (and printk patched to use printascii) I'm receiving following 
> output:
> 
> Uncompressing Linux... done, booting the kernel.
> Booting Linux on physical CPU 0xa00
> Linux version 3.8.0-rc1-00073-gdf6efca-dirty (t.figa at amdc1227) (gcc 
> version 4.5.2 (Gentoo 4.5.2 p1.2, pie-0.4.5) ) #2 SMP PREEMPT Thu Jan 3 
> 15:37:35 CET 2013
> CPU: ARMv7 Processor [413fc090] revision 0 (ARMv7), cr=10c53c7d
> CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
> 
> I tested on two Exynos-based boards (exynos4210-trats and one internal 
> exynos4412-based board) and same happens on both.
> 
> Do you have any ideas?

Another thing besides the things already mentioned is that the dtb may
not cross a 1MiB boundary. The Kernel uses a single 1Mib section
(aligned to 1Mib) to initially map the dtb. Once you cross that boundary
parts of the dtb won't be accessible for the Kernel anymore.

Sascha

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