[OpenWrt-Devel] [PATCH 4/4] ralink: firewrt support memory detect

Felix Fietkau nbd at openwrt.org
Fri Jun 5 03:40:58 EDT 2015

On 2015-06-05 09:30, wbj at t-chip.com.cn wrote:
> Dear sir:
>     I believe that it will work well on other 256mb memory board .
>     But FireWRT has 512mb memory .
>     I am confuse that enable HIGHMEM is not for using 512mb memory ? 
I'm running my code on the FireWRT board with 512M.
I ran memtester with 465M (biggest mmap it could do without causing OOM).

>     Why enable HIGHMEM without using long jump .
kmalloc will only return allocations from low-memory space. As long as
the first 256M are low-mem and the second 256M are high-mem, no
long-jump is needed.

I have another idea for adjusting the code to the memory map you
provided without using long-jump. I'm going to change the highmem start
offset from 0x20000000 to 0x10000000, that way module allocations will
always fit in the 256M boundary.

- Felix
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