Re: generic page.h problem

From: Mike Frysinger
Date: Wed Mar 23 2011 - 15:21:46 EST

On Wed, Mar 23, 2011 at 15:12, Mark Salter wrote:
> I'm working with a new architecture port (nommu) and was wanting to use
> the generic page.h but there is a problem. I'm using CONFIG_FLATMEM with
> a non-zero CONFIG_KERNEL_RAM_BASE_ADDRESS. The hardware uses this same
> address to access RAM from code and for DMA purposes. The generic page.h
> has:
> #else
> #define PAGE_OFFSET Â Â Â Â Â Â (0)
> #endif
> #ifndef __ASSEMBLY__
> #define __va(x) ((void *)((unsigned long)(x) + PAGE_OFFSET))
> #define __pa(x) ((unsigned long) (x) - PAGE_OFFSET)
> The problem I have is that __va(x) and __pa(x) should do nothing on
> this architecture. If I use the following, then everything seems to
> work as it should.
> diff --git a/include/asm-generic/page.h b/include/asm-generic/page.h
> index 75fec18..4dc4a81 100644
> --- a/include/asm-generic/page.h
> +++ b/include/asm-generic/page.h
> @@ -73,8 +73,8 @@ extern unsigned long memory_end;
> Â#ifndef __ASSEMBLY__
> -#define __va(x) ((void *)((unsigned long)(x) + PAGE_OFFSET))
> -#define __pa(x) ((unsigned long) (x) - PAGE_OFFSET)
> +#define __va(x) ((void *)((unsigned long) (x)))
> +#define __pa(x) ((unsigned long) (x))
> Â#define virt_to_pfn(kaddr) Â Â (__pa(kaddr) >> PAGE_SHIFT)
> Â#define pfn_to_virt(pfn) Â Â Â __va((pfn) << PAGE_SHIFT)
> Am I missing something here? The only other arch using the generic
> page.h is blackfin, but it uses a zero PAGE_OFFSET, so my patch
> would have no effect there.

the only arch that defines CONFIG_KERNEL_RAM_BASE_ADDRESS is mn10300,
and it seems that this generic page.h was designed with it in mind.
fwiw, the va/pa defs for mn10300 also ignore PAGE_OFFSET.
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