[PATCH] ARM: fix ioremap to allow mapping some specific RAM areas

[Russell King - ARM Linux]

On Tue, Jun 07, 2011 at 09:12:25AM +0200, Marek Szyprowski wrote:
> Creating more than one mapping on ARMv6+ might cause unspecified behavior,
> so ioremap() should fail if it was called with area that matches low memory.
> However if the board code removes the specific area from low memory
> mapping on boot (for example by calling memblock_remove()), then creating
> a mapping with ioremap might be desired.
> 
> This patch enables creating mapping for RAM by ioremap call, but only if
> the target area has no low memory mapping yet. This enables board code to
> reserve particular memory areas with memblock_remove() and provide them to
> device drivers with a declare_coherent_memory() call.

NAK.  pfn_valid is already defined like this:

int pfn_valid(unsigned long pfn)
{
        return memblock_is_memory(pfn << PAGE_SHIFT);
}

provided you enable ARCH_HAS_HOLES_MEMORYMODEL, which you must do if
you're punching holes in the memory map.