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c8f3570b7e
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> |
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