xref: /openbmc/linux/arch/mips/include/asm/fixmap.h (revision b6dcefde)
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 <asm/page.h>
17 #ifdef CONFIG_HIGHMEM
18 #include <linux/threads.h>
19 #include <asm/kmap_types.h>
20 #endif
21 
22 /*
23  * Here we define all the compile-time 'special' virtual
24  * addresses. The point is to have a constant address at
25  * compile time, but to set the physical address only
26  * in the boot process. We allocate these special  addresses
27  * from the end of virtual memory (0xfffff000) backwards.
28  * Also this lets us do fail-safe vmalloc(), we
29  * can guarantee that these special addresses and
30  * vmalloc()-ed addresses never overlap.
31  *
32  * these 'compile-time allocated' memory buffers are
33  * fixed-size 4k pages. (or larger if used with an increment
34  * highger than 1) use fixmap_set(idx,phys) to associate
35  * physical memory with fixmap indices.
36  *
37  * TLB entries of such buffers will not be flushed across
38  * task switches.
39  */
40 
41 /*
42  * on UP currently we will have no trace of the fixmap mechanizm,
43  * no page table allocations, etc. This might change in the
44  * future, say framebuffers for the console driver(s) could be
45  * fix-mapped?
46  */
47 enum fixed_addresses {
48 #define FIX_N_COLOURS 8
49 	FIX_CMAP_BEGIN,
50 #ifdef CONFIG_MIPS_MT_SMTC
51 	FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * NR_CPUS * 2),
52 #else
53 	FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * 2),
54 #endif
55 #ifdef CONFIG_HIGHMEM
56 	/* reserved pte's for temporary kernel mappings */
57 	FIX_KMAP_BEGIN = FIX_CMAP_END + 1,
58 	FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
59 #endif
60 	__end_of_fixed_addresses
61 };
62 
63 /*
64  * used by vmalloc.c.
65  *
66  * Leave one empty page between vmalloc'ed areas and
67  * the start of the fixmap, and leave one page empty
68  * at the top of mem..
69  */
70 #ifdef CONFIG_BCM63XX
71 #define FIXADDR_TOP     ((unsigned long)(long)(int)0xff000000)
72 #else
73 #if defined(CONFIG_CPU_TX39XX) || defined(CONFIG_CPU_TX49XX)
74 #define FIXADDR_TOP	((unsigned long)(long)(int)(0xff000000 - 0x20000))
75 #else
76 #define FIXADDR_TOP	((unsigned long)(long)(int)0xfffe0000)
77 #endif
78 #endif
79 #define FIXADDR_SIZE	(__end_of_fixed_addresses << PAGE_SHIFT)
80 #define FIXADDR_START	(FIXADDR_TOP - FIXADDR_SIZE)
81 
82 #define __fix_to_virt(x)	(FIXADDR_TOP - ((x) << PAGE_SHIFT))
83 #define __virt_to_fix(x)	((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
84 
85 extern void __this_fixmap_does_not_exist(void);
86 
87 /*
88  * 'index to address' translation. If anyone tries to use the idx
89  * directly without tranlation, we catch the bug with a NULL-deference
90  * kernel oops. Illegal ranges of incoming indices are caught too.
91  */
92 static inline unsigned long fix_to_virt(const unsigned int idx)
93 {
94 	/*
95 	 * this branch gets completely eliminated after inlining,
96 	 * except when someone tries to use fixaddr indices in an
97 	 * illegal way. (such as mixing up address types or using
98 	 * out-of-range indices).
99 	 *
100 	 * If it doesn't get removed, the linker will complain
101 	 * loudly with a reasonably clear error message..
102 	 */
103 	if (idx >= __end_of_fixed_addresses)
104 		__this_fixmap_does_not_exist();
105 
106         return __fix_to_virt(idx);
107 }
108 
109 static inline unsigned long virt_to_fix(const unsigned long vaddr)
110 {
111 	BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
112 	return __virt_to_fix(vaddr);
113 }
114 
115 #define kmap_get_fixmap_pte(vaddr)					\
116 	pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr), (vaddr)), (vaddr)), (vaddr))
117 
118 /*
119  * Called from pgtable_init()
120  */
121 extern void fixrange_init(unsigned long start, unsigned long end,
122         pgd_t *pgd_base);
123 
124 
125 #endif
126