arch/s390/lib/delay.c

   1 /*
   2  *  arch/s390/lib/delay.c
   3  *    Precise Delay Loops for S390
   4  *
   5  *  S390 version
   6  *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
   7  *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com),
   8  *
   9  *  Derived from "arch/i386/lib/delay.c"
  10  *    Copyright (C) 1993 Linus Torvalds
  11  *    Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
  12  */
  13
  14 #include <linux/sched.h>
  15 #include <linux/delay.h>
  16 #include <linux/timex.h>
  17 #include <linux/irqflags.h>
  18
  19 void __delay(unsigned long loops)
  20 {
  21         /*
  22          * To end the bloody studid and useless discussion about the
  23          * BogoMips number I took the liberty to define the __delay
  24          * function in a way that that resulting BogoMips number will
  25          * yield the megahertz number of the cpu. The important function
  26          * is udelay and that is done using the tod clock. -- martin.
  27          */
  28         asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
  29 }
  30
  31 /*
  32  * Waits for 'usecs' microseconds using the TOD clock comparator.
  33  */
  34 void __udelay(unsigned long usecs)
  35 {
  36         u64 end, time, jiffy_timer = 0;
  37         unsigned long flags, cr0, mask, dummy;
  38
  39         local_irq_save(flags);
  40         if (raw_irqs_disabled_flags(flags)) {
  41                 jiffy_timer = S390_lowcore.jiffy_timer;
  42                 S390_lowcore.jiffy_timer = -1ULL - (4096 << 12);
  43                 __ctl_store(cr0, 0, 0);
  44                 dummy = (cr0 & 0xffff00e0) | 0x00000800;
  45                 __ctl_load(dummy , 0, 0);
  46                 mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT;
  47         } else
  48                 mask = psw_kernel_bits | PSW_MASK_WAIT |
  49                         PSW_MASK_EXT | PSW_MASK_IO;
  50
  51         end = get_clock() + ((u64) usecs << 12);
  52         do {
  53                 time = end < S390_lowcore.jiffy_timer ?
  54                         end : S390_lowcore.jiffy_timer;
  55                 set_clock_comparator(time);
  56                 trace_hardirqs_on();
  57                 __load_psw_mask(mask);
  58                 local_irq_disable();
  59         } while (get_clock() < end);
  60
  61         if (raw_irqs_disabled_flags(flags)) {
  62                 __ctl_load(cr0, 0, 0);
  63                 S390_lowcore.jiffy_timer = jiffy_timer;
  64         }
  65         set_clock_comparator(S390_lowcore.jiffy_timer);
  66         local_irq_restore(flags);
  67 }