On Sun, Nov 01, 2015 at 08:24:25PM +0000, Williams, Dan J wrote:
> diff --git a/kernel/memremap.c b/kernel/memremap.c
> index 72b0c66628b6..9d6b55587eaa 100644
> --- a/kernel/memremap.c
> +++ b/kernel/memremap.c
> @@ -24,6 +24,16 @@ __weak void __iomem *ioremap_cache(resource_size_t offset,
> unsigned long size)
> }
> #endif
>
> +static void *try_ram_remap(resource_size_t offset, size_t size)
> +{
> + struct page *page = pfn_to_page(offset >> PAGE_SHIFT);
> +
> + /* In the simple case just return the existing linear address */
> + if (!PageHighMem(page))
> + return __va(offset);
> + return NULL; /* fallback to ioremap_cache */
Right, so a highmem page results in this returning NULL, which will...
> @@ -66,8 +76,8 @@ void *memremap(resource_size_t offset, size_t size,
> unsigned long flags)
> * the requested range is potentially in "System RAM"
> */
> if (is_ram == REGION_INTERSECTS)
> - addr = __va(offset);
> - else
> + addr = try_ram_remap(offset, size);
> + if (!addr)
> addr = ioremap_cache(offset, size);
cause ioremap_cache() to be called. That falls through on ARM to:
__arm_ioremap_pfn_caller()
and we will hit this (as I've mentioned before through explanation
rather than quoting code):
/*
* Don't allow RAM to be mapped - this causes problems with ARMv6+
*/
if (WARN_ON(pfn_valid(pfn)))
return NULL;
--
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
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