From 5f0fbf9ecaf354fa4bbf266fffdea2ea3d14a0ed Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Tue, 16 Sep 2008 13:05:53 -0400 Subject: [ARM] fixmap support This is the minimum fixmap interface expected to be implemented by architectures supporting highmem. We have a second level page table already allocated and covering 0xfff00000-0xffffffff because the exception vector page is located at 0xffff0000, and various cache tricks already use some entries above 0xffff0000. Therefore the PTEs covering 0xfff00000-0xfffeffff are free to be used. However the XScale cache flushing code already uses virtual addresses between 0xfffe0000 and 0xfffeffff. So this reserves the 0xfff00000-0xfffdffff range for fixmap stuff. The Documentation/arm/memory.txt information is updated accordingly, including the information about the actual top of DMA memory mapping region which didn't match the code. Signed-off-by: Nicolas Pitre --- arch/arm/include/asm/fixmap.h | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 arch/arm/include/asm/fixmap.h (limited to 'arch/arm/include/asm/fixmap.h') diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h new file mode 100644 index 000000000000..bbae919bceb4 --- /dev/null +++ b/arch/arm/include/asm/fixmap.h @@ -0,0 +1,41 @@ +#ifndef _ASM_FIXMAP_H +#define _ASM_FIXMAP_H + +/* + * Nothing too fancy for now. + * + * On ARM we already have well known fixed virtual addresses imposed by + * the architecture such as the vector page which is located at 0xffff0000, + * therefore a second level page table is already allocated covering + * 0xfff00000 upwards. + * + * The cache flushing code in proc-xscale.S uses the virtual area between + * 0xfffe0000 and 0xfffeffff. + */ + +#define FIXADDR_START 0xfff00000UL +#define FIXADDR_TOP 0xfffe0000UL +#define FIXADDR_SIZE (FIXADDR_TOP - FIXADDR_START) + +#define FIX_KMAP_BEGIN 0 +#define FIX_KMAP_END (FIXADDR_SIZE >> PAGE_SHIFT) + +#define __fix_to_virt(x) (FIXADDR_START + ((x) << PAGE_SHIFT)) +#define __virt_to_fix(x) (((x) - FIXADDR_START) >> PAGE_SHIFT) + +extern void __this_fixmap_does_not_exist(void); + +static inline unsigned long fix_to_virt(const unsigned int idx) +{ + if (idx >= FIX_KMAP_END) + __this_fixmap_does_not_exist(); + return __fix_to_virt(idx); +} + +static inline unsigned int virt_to_fix(const unsigned long vaddr) +{ + BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START); + return __virt_to_fix(vaddr); +} + +#endif -- cgit