[U-Boot-Users] [PATCH] ppc4xx: Add dcache_enable() for 440

[Stefan Roese]

On Monday 21 April 2008, Wolfgang Denk wrote:
> > This has nothing to do with 440. It's more a general question. But OK,
> > from my
>
> Well, it affects only processors which need MMU support. Most doen't.

I'm not so sure here anymore with all the newer PPC's and other platforms. But 
I have to admit that I'm no expert for those other platforms.

> > understanding, it makes most sense that the i/dcache U-Boot commands
> > touch the cache attributes of all SDRAM related TLB's.
>
> In general, the chackes should be enabled whenever and whereever
> possible.
>
> I think it should be pretty safe to enable the I cache for all SDRAM,
> SRAM and flash areas; or,  put  differently,  for  all  memory  areas
> except maybe any mapped PCI memory windows.
>
> If possible, also D cahce should be enabled, but I cannot judge if
> this works or not with the given driver code.
>
> Also, it depends on where the initial stack and data is located  (you
> probably cannot disable caches if you put initial data in cache).

Another problemtic issue could be the POST area for caches etc. I know that 
self modifying code is used here in some places. This could be more 
problematic with caches enabled.

<snip>

> > And what does this mean that you "insist that this must be fixed for the
> > next release"? I'm sorry, but I personally can't promise to "fix" this
> > issue until the next merge window opens.
>
> Next release means the one that comes after the next merge window.

I did understand this part of the sentence. I'm just not sure what should 
happen with the current code if it doesn't get changed. Again, I personally 
can't promise to "fix" this issue until the next merge window opens.

Best regards,
Stefan

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