[U-Boot] [U-Boot-Users] MIPS: accessing flash > 8MB

[Shinya Kuribayashi <skuribay@pobox.com>]

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.