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authorTrent Piepho <tpiepho@freescale.com>2008-12-08 19:34:59 -0800
committerKumar Gala <galak@kernel.crashing.org>2009-01-28 18:16:53 -0600
commitc8f3570b7e2dd070ba6da41f3ed4ffb4e1d296af (patch)
treee1f8a91bdc37a10583e1b987d5cecf91b9362a30 /arch/powerpc/Kconfig
parentf88747e7f68866f2f82cef1363c5b8e7aa13b0a3 (diff)
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powerpc/fsl-booke: Allow larger CAM sizes than 256 MB
The code that maps kernel low memory would only use page sizes up to 256 MB. On E500v2 pages up to 4 GB are supported. However, a page must be aligned to a multiple of the page's size. I.e. 256 MB pages must aligned to a 256 MB boundary. This was enforced by a requirement that the physical and virtual addresses of the start of lowmem be aligned to 256 MB. Clearly requiring 1GB or 4GB alignment to allow pages of that size isn't acceptable. To solve this, I simply have adjust_total_lowmem() take alignment into account when it decides what size pages to use. Give it PAGE_OFFSET = 0x7000_0000, PHYSICAL_START = 0x3000_0000, and 2GB of RAM, and it will map pages like this: PA 0x3000_0000 VA 0x7000_0000 Size 256 MB PA 0x4000_0000 VA 0x8000_0000 Size 1 GB PA 0x8000_0000 VA 0xC000_0000 Size 256 MB PA 0x9000_0000 VA 0xD000_0000 Size 256 MB PA 0xA000_0000 VA 0xE000_0000 Size 256 MB Because the lowmem mapping code now takes alignment into account, PHYSICAL_ALIGN can be lowered from 256 MB to 64 MB. Even lower might be possible. The lowmem code will work down to 4 kB but it's possible some of the boot code will fail before then. Poor alignment will force small pages to be used, which combined with the limited number of TLB1 pages available, will result in very little memory getting mapped. So alignments less than 64 MB probably aren't very useful anyway. Signed-off-by: Trent Piepho <tpiepho@freescale.com> Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/Kconfig')
-rw-r--r--arch/powerpc/Kconfig2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 74cc312..b408e35 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -794,7 +794,7 @@ config PHYSICAL_START
config PHYSICAL_ALIGN
hex
- default "0x10000000" if FSL_BOOKE
+ default "0x04000000" if FSL_BOOKE
help
This value puts the alignment restrictions on physical address
where kernel is loaded and run from. Kernel is compiled for an