include/linux/mtd/xip.h

   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__ */