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  * $Id: xip.h,v 1.4 2005/10/17 21:03:16 nico Exp $
  16  */
  17
  18 #ifndef __LINUX_MTD_XIP_H__
  19 #define __LINUX_MTD_XIP_H__
  20
  21 #include <linux/config.h>
  22
  23 #ifdef CONFIG_MTD_XIP
  24
  25 /*
  26  * We really don't want gcc to guess anything.
  27  * We absolutely _need_ proper inlining.
  28  */
  29 #include <linux/compiler.h>
  30
  31 /*
  32  * Function that are modifying the flash state away from array mode must
  33  * obviously not be running from flash.  The __xipram is therefore marking
  34  * those functions so they get relocated to ram.
  35  */
  36 #define __xipram noinline __attribute__ ((__section__ (".data")))
  37
  38 /*
  39  * Each architecture has to provide the following macros.  They must access
  40  * the hardware directly and not rely on any other (XIP) functions since they
  41  * won't be available when used (flash not in array mode).
  42  *
  43  * xip_irqpending()
  44  *
  45  *      return non zero when any hardware interrupt is pending.
  46  *
  47  * xip_currtime()
  48  *
  49  *      return a platform specific time reference to be used with
  50  *      xip_elapsed_since().
  51  *
  52  * xip_elapsed_since(x)
  53  *
  54  *      return in usecs the elapsed timebetween now and the reference x as
  55  *      returned by xip_currtime().
  56  *
  57  *      note 1: convertion to usec can be approximated, as long as the
  58  *              returned value is <= the real elapsed time.
  59  *      note 2: this should be able to cope with a few seconds without
  60  *              overflowing.
  61  *
  62  * xip_iprefetch()
  63  *
  64  *      Macro to fill instruction prefetch
  65  *      e.g. a series of nops:  asm volatile (".rep 8; nop; .endr");
  66  */
  67
  68 #include <asm/mtd-xip.h>
  69
  70 #ifndef xip_irqpending
  71
  72 #warning "missing IRQ and timer primitives for XIP MTD support"
  73 #warning "some of the XIP MTD support code will be disabled"
  74 #warning "your system will therefore be unresponsive when writing or erasing flash"
  75
  76 #define xip_irqpending()        (0)
  77 #define xip_currtime()          (0)
  78 #define xip_elapsed_since(x)    (0)
  79
  80 #endif
  81
  82 #ifndef xip_iprefetch
  83 #define xip_iprefetch()         do { } while (0)
  84 #endif
  85
  86 /*
  87  * xip_cpu_idle() is used when waiting for a delay equal or larger than
  88  * the system timer tick period.  This should put the CPU into idle mode
  89  * to save power and to be woken up only when some interrupts are pending.
  90  * This should not rely upon standard kernel code.
  91  */
  92 #ifndef xip_cpu_idle
  93 #define xip_cpu_idle()  do { } while (0)
  94 #endif
  95
  96 #else
  97
  98 #define __xipram
  99
 100 #endif /* CONFIG_MTD_XIP */
 101
 102 #endif /* __LINUX_MTD_XIP_H__ */