Linux Kernel  3.7.1
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xip.h
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1 /*
2  * MTD primitives for XIP support
3  *
4  * Author: Nicolas Pitre
5  * Created: Nov 2, 2004
6  * Copyright: (C) 2004 MontaVista Software, Inc.
7  *
8  * This XIP support for MTD has been loosely inspired
9  * by an earlier patch authored by David Woodhouse.
10  *
11  * This program is free software; you can redistribute it and/or modify
12  * it under the terms of the GNU General Public License version 2 as
13  * published by the Free Software Foundation.
14  */
15 
16 #ifndef __LINUX_MTD_XIP_H__
17 #define __LINUX_MTD_XIP_H__
18 
19 
20 #ifdef CONFIG_MTD_XIP
21 
22 /*
23  * We really don't want gcc to guess anything.
24  * We absolutely _need_ proper inlining.
25  */
26 #include <linux/compiler.h>
27 
28 /*
29  * Function that are modifying the flash state away from array mode must
30  * obviously not be running from flash. The __xipram is therefore marking
31  * those functions so they get relocated to ram.
32  */
33 #define __xipram noinline __attribute__ ((__section__ (".data")))
34 
35 /*
36  * Each architecture has to provide the following macros. They must access
37  * the hardware directly and not rely on any other (XIP) functions since they
38  * won't be available when used (flash not in array mode).
39  *
40  * xip_irqpending()
41  *
42  * return non zero when any hardware interrupt is pending.
43  *
44  * xip_currtime()
45  *
46  * return a platform specific time reference to be used with
47  * xip_elapsed_since().
48  *
49  * xip_elapsed_since(x)
50  *
51  * return in usecs the elapsed timebetween now and the reference x as
52  * returned by xip_currtime().
53  *
54  * note 1: conversion to usec can be approximated, as long as the
55  * returned value is <= the real elapsed time.
56  * note 2: this should be able to cope with a few seconds without
57  * overflowing.
58  *
59  * xip_iprefetch()
60  *
61  * Macro to fill instruction prefetch
62  * e.g. a series of nops: asm volatile (".rep 8; nop; .endr");
63  */
64 
65 #include <asm/mtd-xip.h>
66 
67 #ifndef xip_irqpending
68 
69 #warning "missing IRQ and timer primitives for XIP MTD support"
70 #warning "some of the XIP MTD support code will be disabled"
71 #warning "your system will therefore be unresponsive when writing or erasing flash"
72 
73 #define xip_irqpending() (0)
74 #define xip_currtime() (0)
75 #define xip_elapsed_since(x) (0)
76 
77 #endif
78 
79 #ifndef xip_iprefetch
80 #define xip_iprefetch() do { } while (0)
81 #endif
82 
83 /*
84  * xip_cpu_idle() is used when waiting for a delay equal or larger than
85  * the system timer tick period. This should put the CPU into idle mode
86  * to save power and to be woken up only when some interrupts are pending.
87  * This should not rely upon standard kernel code.
88  */
89 #ifndef xip_cpu_idle
90 #define xip_cpu_idle() do { } while (0)
91 #endif
92 
93 #else
94 
95 #define __xipram
96 
97 #endif /* CONFIG_MTD_XIP */
98 
99 #endif /* __LINUX_MTD_XIP_H__ */