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

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

[Chetan Nanda]

Hi,

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.

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

[Shinya Kuribayashi]

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.