xref: /openbmc/linux/arch/sh/include/asm/fixmap.h (revision a09d2831)
1 /*
2  * fixmap.h: compile-time virtual memory allocation
3  *
4  * This file is subject to the terms and conditions of the GNU General Public
5  * License.  See the file "COPYING" in the main directory of this archive
6  * for more details.
7  *
8  * Copyright (C) 1998 Ingo Molnar
9  *
10  * Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
11  */
12 
13 #ifndef _ASM_FIXMAP_H
14 #define _ASM_FIXMAP_H
15 
16 #include <linux/kernel.h>
17 #include <linux/threads.h>
18 #include <asm/page.h>
19 #ifdef CONFIG_HIGHMEM
20 #include <asm/kmap_types.h>
21 #endif
22 
23 /*
24  * Here we define all the compile-time 'special' virtual
25  * addresses. The point is to have a constant address at
26  * compile time, but to set the physical address only
27  * in the boot process. We allocate these special  addresses
28  * from the end of P3 backwards.
29  * Also this lets us do fail-safe vmalloc(), we
30  * can guarantee that these special addresses and
31  * vmalloc()-ed addresses never overlap.
32  *
33  * these 'compile-time allocated' memory buffers are
34  * fixed-size 4k pages. (or larger if used with an increment
35  * highger than 1) use fixmap_set(idx,phys) to associate
36  * physical memory with fixmap indices.
37  *
38  * TLB entries of such buffers will not be flushed across
39  * task switches.
40  */
41 
42 /*
43  * on UP currently we will have no trace of the fixmap mechanizm,
44  * no page table allocations, etc. This might change in the
45  * future, say framebuffers for the console driver(s) could be
46  * fix-mapped?
47  */
48 enum fixed_addresses {
49 	/*
50 	 * The FIX_CMAP entries are used by kmap_coherent() to get virtual
51 	 * addresses which are of a known color, and so their values are
52 	 * important. __fix_to_virt(FIX_CMAP_END - n) must give an address
53 	 * which is the same color as a page (n<<PAGE_SHIFT).
54 	 */
55 #define FIX_N_COLOURS 8
56 	FIX_CMAP_BEGIN,
57 	FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * NR_CPUS) - 1,
58 	FIX_UNCACHED,
59 #ifdef CONFIG_HIGHMEM
60 	FIX_KMAP_BEGIN,	/* reserved pte's for temporary kernel mappings */
61 	FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
62 #endif
63 	__end_of_fixed_addresses
64 };
65 
66 extern void __set_fixmap(enum fixed_addresses idx,
67 			 unsigned long phys, pgprot_t flags);
68 
69 #define set_fixmap(idx, phys) \
70 		__set_fixmap(idx, phys, PAGE_KERNEL)
71 /*
72  * Some hardware wants to get fixmapped without caching.
73  */
74 #define set_fixmap_nocache(idx, phys) \
75 		__set_fixmap(idx, phys, PAGE_KERNEL_NOCACHE)
76 /*
77  * used by vmalloc.c.
78  *
79  * Leave one empty page between vmalloc'ed areas and
80  * the start of the fixmap, and leave one page empty
81  * at the top of mem..
82  */
83 #ifdef CONFIG_SUPERH32
84 #define FIXADDR_TOP	(P4SEG - PAGE_SIZE)
85 #else
86 #define FIXADDR_TOP	(0xff000000 - PAGE_SIZE)
87 #endif
88 #define FIXADDR_SIZE	(__end_of_fixed_addresses << PAGE_SHIFT)
89 #define FIXADDR_START	(FIXADDR_TOP - FIXADDR_SIZE)
90 
91 #define __fix_to_virt(x)	(FIXADDR_TOP - ((x) << PAGE_SHIFT))
92 #define __virt_to_fix(x)	((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
93 
94 extern void __this_fixmap_does_not_exist(void);
95 
96 /*
97  * 'index to address' translation. If anyone tries to use the idx
98  * directly without tranlation, we catch the bug with a NULL-deference
99  * kernel oops. Illegal ranges of incoming indices are caught too.
100  */
101 static inline unsigned long fix_to_virt(const unsigned int idx)
102 {
103 	/*
104 	 * this branch gets completely eliminated after inlining,
105 	 * except when someone tries to use fixaddr indices in an
106 	 * illegal way. (such as mixing up address types or using
107 	 * out-of-range indices).
108 	 *
109 	 * If it doesn't get removed, the linker will complain
110 	 * loudly with a reasonably clear error message..
111 	 */
112 	if (idx >= __end_of_fixed_addresses)
113 		__this_fixmap_does_not_exist();
114 
115         return __fix_to_virt(idx);
116 }
117 
118 static inline unsigned long virt_to_fix(const unsigned long vaddr)
119 {
120 	BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
121 	return __virt_to_fix(vaddr);
122 }
123 #endif
124