xip.h

 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 __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__ */