[U-Boot] [U-Boot-Users] MIPS: accessing flash > 8MB
Shinya Kuribayashi
skuribay at pobox.com
Sun Jul 26 13:37:54 CEST 2009
Chetan Nanda wrote:
> We have a MIPS-4KEC based SoC and running an older version of U-Boot
> (1.1.3) on it. It is working perfectly fine.
> Board has 8MB AMD flash and starting address of that flash is 0xBFC00000
> (reset vector for MIPS).
>
> Problem is that we are not able to access full 8MB of flash. Only
> 0xBFC00000 - 0xBFFFFFFF (4MB) is accessible, as it lies in un-mapped,
> un-cached region of MIPS.
> From 0xC0000000 lies in mapped memory area of MIPS.
>
> Now my questions are, creating entry in TLBs is sufficient to access
> rest of 4MB of flash?
It depends on its physical address. If your flash device is mapped to
0x1FC00000-0x203FFFFF, you'll need to access to the remaining half via
TLBs.
However, if it's mapped to 0x1F800000-0x1FFFFFFF, no need to set up TLB
entries; you can access anywhere in the devices using KSEG1 virtual
addresses.
> Is their any interface provided in U-boot to update TLB?
There's write_one_tlb() prepared in cpu/mips/cpu.c (I don't know whether
it works or not, as I've never had a chance to use it so far). Lastly,
AFAIK there's no command line interface to do it.
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