arch/openrisc/include/asm/fixmap.h

   1 /*
   2  * OpenRISC Linux
   3  *
   4  * Linux architectural port borrowing liberally from similar works of
   5  * others.  All original copyrights apply as per the original source
   6  * declaration.
   7  *
   8  * OpenRISC implementation:
   9  * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
  10  * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
  11  * et al.
  12  *
  13  * This program is free software; you can redistribute it and/or modify
  14  * it under the terms of the GNU General Public License as published by
  15  * the Free Software Foundation; either version 2 of the License, or
  16  * (at your option) any later version.
  17  */
  18
  19 #ifndef __ASM_OPENRISC_FIXMAP_H
  20 #define __ASM_OPENRISC_FIXMAP_H
  21
  22 /* Why exactly do we need 2 empty pages between the top of the fixed
  23  * addresses and the top of virtual memory?  Something is using that
  24  * memory space but not sure what right now... If you find it, leave
  25  * a comment here.
  26  */
  27 #define FIXADDR_TOP     ((unsigned long) (-2*PAGE_SIZE))
  28
  29 #include <linux/kernel.h>
  30 #include <asm/page.h>
  31
  32 /*
  33  * On OpenRISC we use these special fixed_addresses for doing ioremap
  34  * early in the boot process before memory initialization is complete.
  35  * This is used, in particular, by the early serial console code.
  36  *
  37  * It's not really 'fixmap', per se, but fits loosely into the same
  38  * paradigm.
  39  */
  40 enum fixed_addresses {
  41         /*
  42          * FIX_IOREMAP entries are useful for mapping physical address
  43          * space before ioremap() is useable, e.g. really early in boot
  44          * before kmalloc() is working.
  45          */
  46 #define FIX_N_IOREMAPS  32
  47         FIX_IOREMAP_BEGIN,
  48         FIX_IOREMAP_END = FIX_IOREMAP_BEGIN + FIX_N_IOREMAPS - 1,
  49         __end_of_fixed_addresses
  50 };
  51
  52 #define FIXADDR_SIZE            (__end_of_fixed_addresses << PAGE_SHIFT)
  53 /* FIXADDR_BOTTOM might be a better name here... */
  54 #define FIXADDR_START           (FIXADDR_TOP - FIXADDR_SIZE)
  55
  56 #define __fix_to_virt(x)        (FIXADDR_TOP - ((x) << PAGE_SHIFT))
  57 #define __virt_to_fix(x)        ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
  58
  59 /*
  60  * 'index to address' translation. If anyone tries to use the idx
  61  * directly without tranlation, we catch the bug with a NULL-deference
  62  * kernel oops. Illegal ranges of incoming indices are caught too.
  63  */
  64 static __always_inline unsigned long fix_to_virt(const unsigned int idx)
  65 {
  66         /*
  67          * this branch gets completely eliminated after inlining,
  68          * except when someone tries to use fixaddr indices in an
  69          * illegal way. (such as mixing up address types or using
  70          * out-of-range indices).
  71          *
  72          * If it doesn't get removed, the linker will complain
  73          * loudly with a reasonably clear error message..
  74          */
  75         if (idx >= __end_of_fixed_addresses)
  76                 BUG();
  77
  78         return __fix_to_virt(idx);
  79 }
  80
  81 static inline unsigned long virt_to_fix(const unsigned long vaddr)
  82 {
  83         BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
  84         return __virt_to_fix(vaddr);
  85 }
  86
  87 #endif