[PATCH v8 02/21] acpi: fix acpi_os_ioremap for arm64

On Wed, Feb 04, 2015 at 04:16:34PM +0000, Timur Tabi wrote:

On 02/04/2015 10:08 AM, Mark Salter wrote:

quoted

acpi_os_remap() is used to map ACPI tables. These tables may be in ram
which are already included in the kernel's linear RAM mapping. So we
need ioremap_cache to avoid two mappings to the same physical page
having different caching attributes.

Would it be possible to modify ioremap() so that it can tell whether the 
memory is already mapped in some way, and then use a compatible remapping?

No. We have some semantics for ioremap() and it should return
non-cacheable mapping.

ioremap_cache() checks whether the page is RAM already and returns the
existing kernel linear mapping on arm64.

-- 
Catalin