Re: [microblaze-uclinux] [patch] memory management initialisationcleanup

[John Williams <jwilliams@xxxxxxxxxxxxxx>]

Yasushi SHOJI wrote:

> John Williams wrote:
> 
>>Not quite sure what you mean here - __pa() and __va() macros are already 
>>defined for microblaze in asm-microblaze/page.h  They just reduce to 
>>identity functions of course since physical == virtual for nommu system.
> 
> oops that was bad example.  I just wanted to say that, because we only
> have physical address in microblaze right now, we don't need to use
> __phys_to_virt() and friends in arch/microblaze/*.

I tend to feel that these things should stay in, even if they #define 
down to nothing.  It's like using copyfromuser() in uClinux device 
drivers.  You don't need to use it, and it translates to simple 
memcpy(), but it's still good practice.

> # if we get mmu, we'll call it macroblaze so no need to worry, right? ;p

Hehe - well to be honest I think the chances of seeing microblaze with a 
full MMU are very slim - it really wouldn't make a lot of sense.

What would be more sensible, and probably more interesting, would be a 
limited approach, sort of memory protection unit.  We don't really need 
virtual memory/paging, but basic memory protection would be very nice, 
and more easily implemented in FPGA fabric than a full MMU.

>>Anyway I'll apply the first patch now - it should be ready for cvs 
>>updates shortly.
> 
> 
> I just sync'ed with cvs and compiling...

ok.

I'm just fiddling with DISCONTIGMEM now, it BUG()s in page_alloc(), so 
there's clearly some more to be done.  I'll send a trial patch in the 
next couple of days if you want to have a go at it.

John
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