linux/arch/openrisc/include/asm/fixmap.h
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   1/* SPDX-License-Identifier: GPL-2.0-or-later */
   2/*
   3 * OpenRISC Linux
   4 *
   5 * Linux architectural port borrowing liberally from similar works of
   6 * others.  All original copyrights apply as per the original source
   7 * declaration.
   8 *
   9 * OpenRISC implementation:
  10 * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
  11 * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
  12 * et al.
  13 */
  14
  15#ifndef __ASM_OPENRISC_FIXMAP_H
  16#define __ASM_OPENRISC_FIXMAP_H
  17
  18/* Why exactly do we need 2 empty pages between the top of the fixed
  19 * addresses and the top of virtual memory?  Something is using that
  20 * memory space but not sure what right now... If you find it, leave
  21 * a comment here.
  22 */
  23#define FIXADDR_TOP     ((unsigned long) (-2*PAGE_SIZE))
  24
  25#include <linux/kernel.h>
  26#include <linux/bug.h>
  27#include <asm/page.h>
  28
  29/*
  30 * On OpenRISC we use these special fixed_addresses for doing ioremap
  31 * early in the boot process before memory initialization is complete.
  32 * This is used, in particular, by the early serial console code.
  33 *
  34 * It's not really 'fixmap', per se, but fits loosely into the same
  35 * paradigm.
  36 */
  37enum fixed_addresses {
  38        /*
  39         * FIX_IOREMAP entries are useful for mapping physical address
  40         * space before ioremap() is useable, e.g. really early in boot
  41         * before kmalloc() is working.
  42         */
  43#define FIX_N_IOREMAPS  32
  44        FIX_IOREMAP_BEGIN,
  45        FIX_IOREMAP_END = FIX_IOREMAP_BEGIN + FIX_N_IOREMAPS - 1,
  46        __end_of_fixed_addresses
  47};
  48
  49#define FIXADDR_SIZE            (__end_of_fixed_addresses << PAGE_SHIFT)
  50/* FIXADDR_BOTTOM might be a better name here... */
  51#define FIXADDR_START           (FIXADDR_TOP - FIXADDR_SIZE)
  52
  53#define __fix_to_virt(x)        (FIXADDR_TOP - ((x) << PAGE_SHIFT))
  54#define __virt_to_fix(x)        ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
  55
  56/*
  57 * 'index to address' translation. If anyone tries to use the idx
  58 * directly without tranlation, we catch the bug with a NULL-deference
  59 * kernel oops. Illegal ranges of incoming indices are caught too.
  60 */
  61static __always_inline unsigned long fix_to_virt(const unsigned int idx)
  62{
  63        /*
  64         * this branch gets completely eliminated after inlining,
  65         * except when someone tries to use fixaddr indices in an
  66         * illegal way. (such as mixing up address types or using
  67         * out-of-range indices).
  68         *
  69         * If it doesn't get removed, the linker will complain
  70         * loudly with a reasonably clear error message..
  71         */
  72        if (idx >= __end_of_fixed_addresses)
  73                BUG();
  74
  75        return __fix_to_virt(idx);
  76}
  77
  78static inline unsigned long virt_to_fix(const unsigned long vaddr)
  79{
  80        BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
  81        return __virt_to_fix(vaddr);
  82}
  83
  84#endif
  85