arch/s390/lib/delay.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *    Precise Delay Loops for S390
   4  *
   5  *    Copyright IBM Corp. 1999, 2008
   6  *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
   7  *               Heiko Carstens <heiko.carstens@de.ibm.com>,
   8  */
   9
  10 #include <linux/sched.h>
  11 #include <linux/delay.h>
  12 #include <linux/timex.h>
  13 #include <linux/export.h>
  14 #include <linux/irqflags.h>
  15 #include <linux/interrupt.h>
  16 #include <linux/jump_label.h>
  17 #include <linux/irq.h>
  18 #include <asm/vtimer.h>
  19 #include <asm/div64.h>
  20 #include <asm/idle.h>
  21
  22 void __delay(unsigned long loops)
  23 {
  24         /*
  25          * To end the bloody studid and useless discussion about the
  26          * BogoMips number I took the liberty to define the __delay
  27          * function in a way that that resulting BogoMips number will
  28          * yield the megahertz number of the cpu. The important function
  29          * is udelay and that is done using the tod clock. -- martin.
  30          */
  31         asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
  32 }
  33 EXPORT_SYMBOL(__delay);
  34
  35 static void delay_loop(unsigned long delta)
  36 {
  37         unsigned long end;
  38
  39         end = get_tod_clock_monotonic() + delta;
  40         while (!tod_after(get_tod_clock_monotonic(), end))
  41                 cpu_relax();
  42 }
  43
  44 void __udelay(unsigned long usecs)
  45 {
  46         delay_loop(usecs << 12);
  47 }
  48 EXPORT_SYMBOL(__udelay);
  49
  50 void __ndelay(unsigned long nsecs)
  51 {
  52         nsecs <<= 9;
  53         do_div(nsecs, 125);
  54         delay_loop(nsecs);
  55 }
  56 EXPORT_SYMBOL(__ndelay);