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authorNicolas Pitre <nico@cam.org>2008-09-16 13:05:53 -0400
committerNicolas Pitre <nico@cam.org>2009-03-15 21:01:20 -0400
commit5f0fbf9ecaf354fa4bbf266fffdea2ea3d14a0ed (patch)
tree9f0c59760b2bec510519118ddb17d4b15db473f5 /arch
parent1522ac3ec95ff0230e7aa516f86b674fdf72866c (diff)
downloadlinux-5f0fbf9ecaf354fa4bbf266fffdea2ea3d14a0ed.tar.gz
[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 <nico@marvell.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm/include/asm/fixmap.h41
-rw-r--r--arch/arm/mm/mm.h3
2 files changed, 42 insertions, 2 deletions
diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
new file mode 100644
index 00000000000..bbae919bceb
--- /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
diff --git a/arch/arm/mm/mm.h b/arch/arm/mm/mm.h
index 95bbe112965..c4f6f05198e 100644
--- a/arch/arm/mm/mm.h
+++ b/arch/arm/mm/mm.h
@@ -1,7 +1,6 @@
-/* the upper-most page table pointer */
-
#ifdef CONFIG_MMU
+/* the upper-most page table pointer */
extern pmd_t *top_pmd;
#define TOP_PTE(x) pte_offset_kernel(top_pmd, x)