arch/sh/include/asm/fixmap.h

   1 /*
   2  * fixmap.h: compile-time virtual memory allocation
   3  *
   4  * This file is subject to the terms and conditions of the GNU General Public
   5  * License.  See the file "COPYING" in the main directory of this archive
   6  * for more details.
   7  *
   8  * Copyright (C) 1998 Ingo Molnar
   9  *
  10  * Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
  11  */
  12
  13 #ifndef _ASM_FIXMAP_H
  14 #define _ASM_FIXMAP_H
  15
  16 #include <linux/kernel.h>
  17 #include <linux/threads.h>
  18 #include <asm/page.h>
  19 #ifdef CONFIG_HIGHMEM
  20 #include <asm/kmap_types.h>
  21 #endif
  22
  23 /*
  24  * Here we define all the compile-time 'special' virtual
  25  * addresses. The point is to have a constant address at
  26  * compile time, but to set the physical address only
  27  * in the boot process. We allocate these special  addresses
  28  * from the end of P3 backwards.
  29  * Also this lets us do fail-safe vmalloc(), we
  30  * can guarantee that these special addresses and
  31  * vmalloc()-ed addresses never overlap.
  32  *
  33  * these 'compile-time allocated' memory buffers are
  34  * fixed-size 4k pages. (or larger if used with an increment
  35  * highger than 1) use fixmap_set(idx,phys) to associate
  36  * physical memory with fixmap indices.
  37  *
  38  * TLB entries of such buffers will not be flushed across
  39  * task switches.
  40  */
  41
  42 /*
  43  * on UP currently we will have no trace of the fixmap mechanizm,
  44  * no page table allocations, etc. This might change in the
  45  * future, say framebuffers for the console driver(s) could be
  46  * fix-mapped?
  47  */
  48 enum fixed_addresses {
  49         /*
  50          * The FIX_CMAP entries are used by kmap_coherent() to get virtual
  51          * addresses which are of a known color, and so their values are
  52          * important. __fix_to_virt(FIX_CMAP_END - n) must give an address
  53          * which is the same color as a page (n<<PAGE_SHIFT).
  54          */
  55 #define FIX_N_COLOURS 8
  56         FIX_CMAP_BEGIN,
  57         FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * NR_CPUS) - 1,
  58
  59 #ifdef CONFIG_HIGHMEM
  60         FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
  61         FIX_KMAP_END = FIX_KMAP_BEGIN + (KM_TYPE_NR * NR_CPUS) - 1,
  62 #endif
  63
  64 #ifdef CONFIG_IOREMAP_FIXED
  65         /*
  66          * FIX_IOREMAP entries are useful for mapping physical address
  67          * space before ioremap() is useable, e.g. really early in boot
  68          * before kmalloc() is working.
  69          */
  70 #define FIX_N_IOREMAPS  32
  71         FIX_IOREMAP_BEGIN,
  72         FIX_IOREMAP_END = FIX_IOREMAP_BEGIN + FIX_N_IOREMAPS - 1,
  73 #endif
  74
  75         __end_of_fixed_addresses
  76 };
  77
  78 extern void __set_fixmap(enum fixed_addresses idx,
  79                          unsigned long phys, pgprot_t flags);
  80 extern void __clear_fixmap(enum fixed_addresses idx, pgprot_t flags);
  81
  82 #define set_fixmap(idx, phys) \
  83                 __set_fixmap(idx, phys, PAGE_KERNEL)
  84 /*
  85  * Some hardware wants to get fixmapped without caching.
  86  */
  87 #define set_fixmap_nocache(idx, phys) \
  88                 __set_fixmap(idx, phys, PAGE_KERNEL_NOCACHE)
  89 /*
  90  * used by vmalloc.c.
  91  *
  92  * Leave one empty page between vmalloc'ed areas and
  93  * the start of the fixmap, and leave one page empty
  94  * at the top of mem..
  95  */
  96 #ifdef CONFIG_SUPERH32
  97 #define FIXADDR_TOP     (P4SEG - PAGE_SIZE)
  98 #else
  99 #define FIXADDR_TOP     (0xff000000 - PAGE_SIZE)
 100 #endif
 101 #define FIXADDR_SIZE    (__end_of_fixed_addresses << PAGE_SHIFT)
 102 #define FIXADDR_START   (FIXADDR_TOP - FIXADDR_SIZE)
 103
 104 #define __fix_to_virt(x)        (FIXADDR_TOP - ((x) << PAGE_SHIFT))
 105 #define __virt_to_fix(x)        ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
 106
 107 extern void __this_fixmap_does_not_exist(void);
 108
 109 /*
 110  * 'index to address' translation. If anyone tries to use the idx
 111  * directly without tranlation, we catch the bug with a NULL-deference
 112  * kernel oops. Illegal ranges of incoming indices are caught too.
 113  */
 114 static inline unsigned long fix_to_virt(const unsigned int idx)
 115 {
 116         /*
 117          * this branch gets completely eliminated after inlining,
 118          * except when someone tries to use fixaddr indices in an
 119          * illegal way. (such as mixing up address types or using
 120          * out-of-range indices).
 121          *
 122          * If it doesn't get removed, the linker will complain
 123          * loudly with a reasonably clear error message..
 124          */
 125         if (idx >= __end_of_fixed_addresses)
 126                 __this_fixmap_does_not_exist();
 127
 128         return __fix_to_virt(idx);
 129 }
 130
 131 static inline unsigned long virt_to_fix(const unsigned long vaddr)
 132 {
 133         BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
 134         return __virt_to_fix(vaddr);
 135 }
 136 #endif