arch/openrisc/include/asm/fixmap.h

   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  */
  37 enum 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  */
  61 static __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
  78 static 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