xref: /openbmc/linux/arch/openrisc/include/asm/fixmap.h (revision b4e18b29)
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
85