On Sat, Jun 6, 2015 at 8:29 AM, Stefan Agner <[email protected]> wrote: > On 2015-06-06 14:48, Russell King - ARM Linux wrote: >> On Sat, Jun 06, 2015 at 02:31:28PM +0200, Stefan Agner wrote: > <snip> >>> --- a/arch/arm/include/asm/fixmap.h >>> +++ b/arch/arm/include/asm/fixmap.h >>> @@ -6,9 +6,13 @@ >>> #define FIXADDR_TOP (FIXADDR_END - PAGE_SIZE) >>> >>> #include <asm/kmap_types.h> >>> +#include <asm/pgtable.h> >>> >>> enum fixed_addresses { >>> - FIX_KMAP_BEGIN, >>> + FIX_EARLYCON_MEM_BASE, >>> + __end_of_permanent_fixed_addresses, >>> + >>> + FIX_KMAP_BEGIN = __end_of_permanent_fixed_addresses, >>> FIX_KMAP_END = FIX_KMAP_BEGIN + (KM_TYPE_NR * NR_CPUS) - 1, >>> >>> /* Support writing RO kernel text via kprobes, jump labels, etc. */ >>> @@ -18,7 +22,14 @@ enum fixed_addresses { >>> __end_of_fixed_addresses >>> }; >>> >>> +#define FIXMAP_PAGE_COMMON (L_PTE_YOUNG | L_PTE_PRESENT | L_PTE_XN | >>> L_PTE_DIRTY) >>> + >>> +#define FIXMAP_PAGE_NORMAL (FIXMAP_PAGE_COMMON | L_PTE_MT_WRITEBACK) >>> +#define FIXMAP_PAGE_IO (FIXMAP_PAGE_COMMON | >>> L_PTE_MT_DEV_SHARED | L_PTE_SHARED) >>> +#define FIXMAP_PAGE_NOCACHE FIXMAP_PAGE_IO >> >> I'm really not happy with this. What are the expected semantics of the >> set_fixmap_nocache() and set_fixmap_offset_nocache() ? Are they there >> for mapping a device, or are they there for mapping _memory_ ? >> >> I would prefer that FIXMAP_PAGE_NOCACHE is _not_ provided until the >> semantics of that can be clarified, as there is a difference between the >> two on ARM. > > set_fixmap_nocache is used for PCIe and IO APIC stuff, so actually IO > devices. However, as far as I understand the x86 page table definitions > in pgtable_types.h, IO devices are not explicitly uncached on x86. The > define set_fixmap_nocache make sure IO devices are mapped uncached... > Maybe set_fixmap_io_nocache instead of set_fixmap_nocache would be more > appropriate...? > > Maybe the initial authors of the common fixmap.h have a more clear > understanding of the expected semantics, Mark?
They should be the same as ioremap and ioremap_nocache which are aliases of each other on ARM. If you want RAM then you should be using FIXMAP_PAGE_NORMAL. Perhaps we can come up with some error checking here. > Since the focus currently is on set_fixmap_io, we could define > FIXMAP_PAGE_IO only for the time being...? We could, but I think it is better to sort this out now. Rob -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
