On Thu, 2015-02-05 at 10:41 +0000, Catalin Marinas wrote:
On Wed, Feb 04, 2015 at 06:58:14PM +0000, Mark Salter wrote:
On Wed, 2015-02-04 at 17:57 +0000, Catalin Marinas wrote:
On Wed, Feb 04, 2015 at 04:08:27PM +0000, Mark Salter wrote:
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.
What's the call path to acpi_os_ioremap() on such tables already in the linear mapping? I can see an acpi_map() function which already takes care of the RAM mapping case but there are other cases where acpi_os_ioremap() is called directly. For example, acpi_os_read_memory(), can it be called on both RAM and I/O?
acpi_map() is the one I've seen.
By default, if should_use_kmap() is not patched for arm64, it translates to page_is_ram(); acpi_map() would simply use a kmap() which returns the current kernel linear mapping on arm64.
The problem with kmap() is that it only maps a single page. I've seen tables over 4k which is why I patched acpi_map() not to use kmap() on arm64.
I'm not sure about others.
Question for the ARM ACPI guys: what happens if you implement acpi_os_ioremap() on arm64 as just ioremap()? Do you get any WARN_ON() (__ioremap_caller() checks whether the memory is RAM)?