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fixmap.h
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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 <[email protected]>
10  * Copyright (C) 2010-2011 Jonas Bonn <[email protected]>
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  */
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
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