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:
#ifdef CONFIG_KERNEL_RAM_BASE_ADDRESS
#define PAGE_OFFSET (CONFIG_KERNEL_RAM_BASE_ADDRESS)
#else
#define PAGE_OFFSET (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;
#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))
#define virt_to_pfn(kaddr) (__pa(kaddr) >> PAGE_SHIFT)
#define pfn_to_virt(pfn) __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.
--Mark
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:
>
> #ifdef CONFIG_KERNEL_RAM_BASE_ADDRESS
> #define PAGE_OFFSET (CONFIG_KERNEL_RAM_BASE_ADDRESS)
> #else
> #define PAGE_OFFSET (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;
>
> #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))
>
> #define virt_to_pfn(kaddr) (__pa(kaddr) >> PAGE_SHIFT)
> #define pfn_to_virt(pfn) __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.
-mike
On Wednesday 23 March 2011 20:12:53 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:
>
> #ifdef CONFIG_KERNEL_RAM_BASE_ADDRESS
> #define PAGE_OFFSET (CONFIG_KERNEL_RAM_BASE_ADDRESS)
> #else
> #define PAGE_OFFSET (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;
>
> #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))
>
> #define virt_to_pfn(kaddr) (__pa(kaddr) >> PAGE_SHIFT)
> #define pfn_to_virt(pfn) __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.
I don't think the handling of nonzero PAGE_OFFSET in asm-generic/page.h
was intentional. When Remis worked on the patch to introduce this file,
the idea was to take the common parts from all related architectures
and come up with a way that works on most of them.
Maybe one of the other arch maintainers has an opinion on this. If
not, I don't mind your patch, just add that to your series when submitting
the architecture for review.
Arnd