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 #ifdef CONFIG_XIP_KERNEL
  34 #define __xipram noinline __attribute__ ((__section__ (".xiptext")))
  35 #endif
  36
  37 /*
  38  * Each architecture has to provide the following macros.  They must access
  39  * the hardware directly and not rely on any other (XIP) functions since they
  40  * won't be available when used (flash not in array mode).
  41  *
  42  * xip_irqpending()
  43  *
  44  *      return non zero when any hardware interrupt is pending.
  45  *
  46  * xip_currtime()
  47  *
  48  *      return a platform specific time reference to be used with
  49  *      xip_elapsed_since().
  50  *
  51  * xip_elapsed_since(x)
  52  *
  53  *      return in usecs the elapsed timebetween now and the reference x as
  54  *      returned by xip_currtime().
  55  *
  56  *      note 1: conversion to usec can be approximated, as long as the
  57  *              returned value is <= the real elapsed time.
  58  *      note 2: this should be able to cope with a few seconds without
  59  *              overflowing.
  60  *
  61  * xip_iprefetch()
  62  *
  63  *      Macro to fill instruction prefetch
  64  *      e.g. a series of nops:  asm volatile (".rep 8; nop; .endr");
  65  */
  66
  67 #include <asm/mtd-xip.h>
  68
  69 #ifndef xip_irqpending
  70
  71 #warning "missing IRQ and timer primitives for XIP MTD support"
  72 #warning "some of the XIP MTD support code will be disabled"
  73 #warning "your system will therefore be unresponsive when writing or erasing flash"
  74
  75 #define xip_irqpending()        (0)
  76 #define xip_currtime()          (0)
  77 #define xip_elapsed_since(x)    (0)
  78
  79 #endif
  80
  81 #ifndef xip_iprefetch
  82 #define xip_iprefetch()         do { } while (0)
  83 #endif
  84
  85 /*
  86  * xip_cpu_idle() is used when waiting for a delay equal or larger than
  87  * the system timer tick period.  This should put the CPU into idle mode
  88  * to save power and to be woken up only when some interrupts are pending.
  89  * This should not rely upon standard kernel code.
  90  */
  91 #ifndef xip_cpu_idle
  92 #define xip_cpu_idle()  do { } while (0)
  93 #endif
  94
  95 #endif /* CONFIG_MTD_XIP */
  96
  97 #ifndef __xipram
  98 #define __xipram
  99 #endif
 100
 101 #endif /* __LINUX_MTD_XIP_H__ */