About ARM TCM patch

[Peter Chen]

On Sat, 2009-09-26 at 23:58 +0200, Linus Walleij wrote:
> 2009/9/25 Linus Walleij <linus.ml.walleij at gmail.com>:
> > 2009/9/25 Peter Chen <hzpeterchen at gmail.com>:
> 
> >> 1. After MMU open, the code running at ITCM can't see physical address for
> >> register.
> >>
> >> 2. After MMU open, the code can't run at physical addressed ITCM.
> >
> > Could this be different between ARM9 (which I use) and ARM11?
> 
> Thinking about it this rings a bell. I know it behaves like described on ARM9,
> so code executing in TCM can only "see" physical memory.
> 
> But one difference between the ARM9 and ARM11 families is that the cache
> is mapped to virtual (MMU:ed) address space in ARM9 and to physical address
> space in ARM11 is it not? (Is this so already in ARM10 BTW?)
> 
> So just thinking intuitively about it, as a TCM memory is very close to what
> a cache is to the CPU I think it's something like this on ARM9:
> 
>      CPU
>      / \
> Cache   TCM
>   |      |
>  MMU     |
>   |      |
> External memory interface
> 
> But on ARM11 (ARM10?):
> 
>      CPU
>       |
>      MMU
>      / \
> Cache   TCM
>   |
> External memory interface
> 
> Is that correct more or less? Catalin would you happen to know this?
I think you are right. 

> Anyway the code should still work actually, since we make a 1-1 memory
> map anyway. But you cannot place the TCM in the memory locations I
> chose for U300 since these are occupied on ARM11.
Sorry, I haven't tried your patch at kernel, I just did experiments at u-boot.


> Linus Walleij
-- 
Best Regards
Peter Chen