1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * MTD primitives for XIP support
4 *
5 * Author: Nicolas Pitre
6 * Created: Nov 2, 2004
7 * Copyright: (C) 2004 MontaVista Software, Inc.
8 *
9 * This XIP support for MTD has been loosely inspired
10 * by an earlier patch authored by David Woodhouse.
11 */
12
13 #ifndef __LINUX_MTD_XIP_H__
14 #define __LINUX_MTD_XIP_H__
15
16
17 #ifdef CONFIG_MTD_XIP
18
19 /*
20 * We really don't want gcc to guess anything.
21 * We absolutely _need_ proper inlining.
22 */
23 #include <linux/compiler.h>
24
25 /*
26 * Function that are modifying the flash state away from array mode must
27 * obviously not be running from flash. The __xipram is therefore marking
28 * those functions so they get relocated to ram.
29 */
30 #ifdef CONFIG_XIP_KERNEL
31 #define __xipram noinline __attribute__ ((__section__ (".xiptext")))
32 #endif
33
34 /*
35 * Each architecture has to provide the following macros. They must access
36 * the hardware directly and not rely on any other (XIP) functions since they
37 * won't be available when used (flash not in array mode).
38 *
39 * xip_irqpending()
40 *
41 * return non zero when any hardware interrupt is pending.
42 *
43 * xip_currtime()
44 *
45 * return a platform specific time reference to be used with
46 * xip_elapsed_since().
47 *
48 * xip_elapsed_since(x)
49 *
50 * return in usecs the elapsed timebetween now and the reference x as
51 * returned by xip_currtime().
52 *
53 * note 1: conversion to usec can be approximated, as long as the
54 * returned value is <= the real elapsed time.
55 * note 2: this should be able to cope with a few seconds without
56 * overflowing.
57 *
58 * xip_iprefetch()
59 *
60 * Macro to fill instruction prefetch
61 * e.g. a series of nops: asm volatile (".rep 8; nop; .endr");
62 */
63
64 #include <asm/mtd-xip.h>
65
66 #ifndef xip_irqpending
67
68 #warning "missing IRQ and timer primitives for XIP MTD support"
69 #warning "some of the XIP MTD support code will be disabled"
70 #warning "your system will therefore be unresponsive when writing or erasing flash"
71
72 #define xip_irqpending() (0)
73 #define xip_currtime() (0)
74 #define xip_elapsed_since(x) (0)
75
76 #endif
77
78 #ifndef xip_iprefetch
79 #define xip_iprefetch() do { } while (0)
80 #endif
81
82 /*
83 * xip_cpu_idle() is used when waiting for a delay equal or larger than
84 * the system timer tick period. This should put the CPU into idle mode
85 * to save power and to be woken up only when some interrupts are pending.
86 * This should not rely upon standard kernel code.
87 */
88 #ifndef xip_cpu_idle
89 #define xip_cpu_idle() do { } while (0)
90 #endif
91
92 #endif /* CONFIG_MTD_XIP */
93
94 #ifndef __xipram
95 #define __xipram
96 #endif
97
98 #endif /* __LINUX_MTD_XIP_H__ */