LXR linux/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 */
  40enum 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 */
  64static __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
  81static 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
  88