Messages in this thread Patch in this message | | | Date | Sun, 1 Nov 2015 20:36:56 +0000 | From | Russell King - ARM Linux <> | Subject | Re: [GIT PULL] memremap fix for 4.3 (v2) |
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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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