On Thu, Feb 05, 2015 at 12:07:20PM +0000, Catalin Marinas wrote: > On Thu, Feb 05, 2015 at 11:14:43AM +0000, Graeme Gregory wrote: > > On Thu, Feb 05, 2015 at 10:59:45AM +0000, Catalin Marinas wrote: > > > On Thu, Feb 05, 2015 at 10:47:23AM +0000, Ard Biesheuvel wrote: > > > > On 5 February 2015 at 10:41, Catalin Marinas <catalin.marinas@xxxxxxx> 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. > > > > > > > > > >> 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)? > > > > > > > > Regardless of whether you hit any WARN_ON()s now, > > > > > > Actually following the WARN_ON(), ioremap() returns NULL, so it may not > > > go entirely unnoticed. > > > > > > > we still need to distinguish between MMIO ranges with device > > > > semantics, and ACPI or other tables whose data may not be naturally > > > > aligned all the time, and hence requiring memory semantics. > > > > acpi_os_ioremap() may be used for both, afaik > > > > > > Is acpi_os_ioremap() called directly (outside acpi_map()) to map RAM > > > that already part of the kernel linear memory? If yes, then I agree that > > > we need to do such check. > > > > > > Another question, can we distinguish, in the ACPI core code, whether the > > > mapping is for an ACPI table in RAM or some I/O space? > > > > Yes I think we do, > > > > acpi_os_map_memory() is called to map tables > > > > acpi_os_map_iomem() is called to map device IO > > > > currently both end up in acpi_map but I guess they do not have to or > > we can add extra arguments as its an internal API. > > Ending up in acpi_map() is ok as this function checks whether it should > use kmap() or acpi_os_ioremap(). > > > But I have not checked that no user sneaks in direct calls. > > Grep'ing for acpi_os_ioremap(): > > suspend_nvs_save() - we don't care about this yet for arm64 as the > function is only compiled in if CONFIG_ACPI_SLEEP > > acpi_os_read_memory() and acpi_os_write_memory() - do you know what kind > of memory are these used on? > They are used when an operating region is set to SystemMemory type. >From table 19-326 Region Type: SystemMemory Permitted Access Type: ByteAcc, WordAcc, DWordAcc, QWordAcc, or AnyAcc Description: All access allowed Graeme > couple of intel drm files that are not used on arm. > > -- > Catalin > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
