Hi Ira & Wolfgang,
On Friday 10 September 2010 13:18:55 Wolfgang Denk wrote:
Does anyone know the true maximum value for CONFIG_SYS_BOOTMAPSZ on Linux (if one even exists)?
The CONFIG_SYS_BOOTMAPSZ thing is as old as U-Boot and PPCBoot exists, i. e. well over a decade. IIRC there was such a limitation on the then current 2.2.13 Linux kernels, at least on MPC8xx and PPC40x systems, which is where all started from.
I am pretty sure that as long as nobody ran into any problems, nobody looked into that code, so it was copied from architecture to architecture without much thinking, if any.
I looked at it a bit over a year ago and commited this change for the AMCC/APM eval boards:
commit 6942efc2be1b90054fa4afa5cda7023469fe08b9 Author: Stefan Roese sr@denx.de Date: Tue Jul 28 10:50:32 2009 +0200
ppc4xx: amcc: Set CONFIG_SYS_BOOTMAPSZ to 16MB for big kernels
This patch changes CONFIG_SYS_BOOTMAPSZ from 8MB to 16MB which is the initial TLB on 40x PPC's in the Linux kernel. With this change even bigger Linux kernels (> 8MB) can be booted.
This patch also sets CONFIG_SYS_BOOTM_LEN to 16MB (default 8MB) to enable decompression of bigger images.
Signed-off-by: Stefan Roese sr@denx.de
So we have this 16MiB initial TLB restriction at least for PPC405 (not PPC440). I'm pretty sure that 83xx has no such tight restrictions.
Cheers, Stefan
-- DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-0 Fax: (+49)-8142-66989-80 Email: office@denx.de