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
  27 void __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 }
  37 EXPORT_SYMBOL(__delay);
  38
  39 inline void __const_udelay(unsigned long xloops)
  40 {
  41         u64 loops = (u64)xloops * (u64)loops_per_jiffy * HZ;
  42         __delay(loops >> 32);
  43 }
  44 EXPORT_SYMBOL(__const_udelay);
  45
  46 void __udelay(unsigned long usecs)
  47 {
  48         __const_udelay(usecs * 0x000010c7); /* 2**32 / 1000000 (rounded up) */
  49 }
  50 EXPORT_SYMBOL(__udelay);
  51
  52 void __ndelay(unsigned long nsecs)
  53 {
  54         __const_udelay(nsecs * 0x00005); /* 2**32 / 1000000000 (rounded up) */
  55 }
  56 EXPORT_SYMBOL(__ndelay);