On Fri, 2015-07-24 at 17:26 +0100, Will Deacon wrote: > On Fri, Jul 24, 2015 at 05:21:49PM +0100, Catalin Marinas wrote: > > On Fri, Jul 24, 2015 at 03:57:08PM +0100, Will Deacon wrote: > > > On Tue, Jul 21, 2015 at 10:59:19PM +0100, Jonathan (Zhixiong) Zhang wrote: > > > > diff --git a/arch/arm64/include/asm/acpi.h > > > > b/arch/arm64/include/asm/acpi.h > > > > +static inline pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr) > > > > +{ > > > > + pgprot_t prot; > > > > + > > > > + prot = efi_mem_attributes(addr); > > > > + if (prot & EFI_MEMORY_UC) > > > > + return PROT_DEVICE_nGnRnE; > > > > + if (prot & EFI_MEMORY_WC) > > > > + return PROT_NORMAL_NC; > > > > > > Can we not use pgprot_noncached and pgprot_writecombine for these two? > > > > Actually, why do we even use pgprot_t for prot here? EFI_MEMORY_* don't > > have anything to do with the arch-specific pgprot_t. > > Good point; the pgprot_t confused me, so my suggestion is much use after > ll. We're better off with a u64 to avoid further confusion.
Isn't the whole point of arch_apei_get_mem_attribute() to turn an arch-independent memory attribute (EFI_MEMORY_*) into an arch-specific value to pass to ioremap_page_range()? I don't see how you can do that any other way than by using pgprot_t. Really, the problem here is that ioremap_page_caller() has no notion of "map this range in a firmware-compatible manner". If we could do, for example, ioremap_page_range(vaddr, vend, paddr, PAGE_FW_COMPAT); that would allow the innards of the arch-ioremap to figure out exactly how to map this range so that the firmware could access it coherently. I suggested this previously but it didn't gain any traction. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/