include/linux/mtd/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 __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__ */