LXR linux/arch/metag/lib/delay.c

   1/*
   2 *      Precise Delay Loops for Meta
   3 *
   4 *      Copyright (C) 1993 Linus Torvalds
   5 *      Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
   6 *      Copyright (C) 2007,2009 Imagination Technologies Ltd.
   7 *
   8 */
   9
  10#include <linux/export.h>
  11#include <linux/sched.h>
  12#include <linux/delay.h>
  13
  14#include <asm/core_reg.h>
  15#include <asm/processor.h>
  16
  17/*
  18 * TXTACTCYC is only 24 bits, so on chips with fast clocks it will wrap
  19 * many times per-second. If it does wrap __delay will return prematurely,
  20 * but this is only likely with large delay values.
  21 *
  22 * We also can't implement read_current_timer() with TXTACTCYC due to
  23 * this wrapping behaviour.
  24 */
  25#define rdtimer(t) t = __core_reg_get(TXTACTCYC)
  26
  27void __delay(unsigned long loops)
  28{
  29        unsigned long bclock, now;
  30
  31        rdtimer(bclock);
  32        do {
  33                asm("NOP");
  34                rdtimer(now);
  35        } while ((now-bclock) < loops);
  36}
  37EXPORT_SYMBOL(__delay);
  38
  39inline void __const_udelay(unsigned long xloops)
  40{
  41        u64 loops = (u64)xloops * (u64)loops_per_jiffy * HZ;
  42        __delay(loops >> 32);
  43}
  44EXPORT_SYMBOL(__const_udelay);
  45
  46void __udelay(unsigned long usecs)
  47{
  48        __const_udelay(usecs * 0x000010c7); /* 2**32 / 1000000 (rounded up) */
  49}
  50EXPORT_SYMBOL(__udelay);
  51
  52void __ndelay(unsigned long nsecs)
  53{
  54        __const_udelay(nsecs * 0x00005); /* 2**32 / 1000000000 (rounded up) */
  55}
  56EXPORT_SYMBOL(__ndelay);
  57