arch/metag/lib/delay.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *      Precise Delay Loops for Meta
   4  *
   5  *      Copyright (C) 1993 Linus Torvalds
   6  *      Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
   7  *      Copyright (C) 2007,2009 Imagination Technologies Ltd.
   8  *
   9  */
  10
  11 #include <linux/export.h>
  12 #include <linux/sched.h>
  13 #include <linux/delay.h>
  14
  15 #include <asm/core_reg.h>
  16 #include <asm/processor.h>
  17
  18 /*
  19  * TXTACTCYC is only 24 bits, so on chips with fast clocks it will wrap
  20  * many times per-second. If it does wrap __delay will return prematurely,
  21  * but this is only likely with large delay values.
  22  *
  23  * We also can't implement read_current_timer() with TXTACTCYC due to
  24  * this wrapping behaviour.
  25  */
  26 #define rdtimer(t) t = __core_reg_get(TXTACTCYC)
  27
  28 void __delay(unsigned long loops)
  29 {
  30         unsigned long bclock, now;
  31
  32         rdtimer(bclock);
  33         do {
  34                 asm("NOP");
  35                 rdtimer(now);
  36         } while ((now-bclock) < loops);
  37 }
  38 EXPORT_SYMBOL(__delay);
  39
  40 inline void __const_udelay(unsigned long xloops)
  41 {
  42         u64 loops = (u64)xloops * (u64)loops_per_jiffy * HZ;
  43         __delay(loops >> 32);
  44 }
  45 EXPORT_SYMBOL(__const_udelay);
  46
  47 void __udelay(unsigned long usecs)
  48 {
  49         __const_udelay(usecs * 0x000010c7); /* 2**32 / 1000000 (rounded up) */
  50 }
  51 EXPORT_SYMBOL(__udelay);
  52
  53 void __ndelay(unsigned long nsecs)
  54 {
  55         __const_udelay(nsecs * 0x00005); /* 2**32 / 1000000000 (rounded up) */
  56 }
  57 EXPORT_SYMBOL(__ndelay);