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delay.c

/*
 *  arch/s390/lib/delay.c
 *    Precise Delay Loops for S390
 *
 *  S390 version
 *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
 *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com),
 *
 *  Derived from "arch/i386/lib/delay.c"
 *    Copyright (C) 1993 Linus Torvalds
 *    Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
 */

#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/timex.h>
#include <linux/irqflags.h>
#include <linux/interrupt.h>

void __delay(unsigned long loops)
{
        /*
         * To end the bloody studid and useless discussion about the
         * BogoMips number I took the liberty to define the __delay
         * function in a way that that resulting BogoMips number will
         * yield the megahertz number of the cpu. The important function
         * is udelay and that is done using the tod clock. -- martin.
         */
      asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
}

/*
 * Waits for 'usecs' microseconds using the TOD clock comparator.
 */
void __udelay(unsigned long usecs)
{
      u64 end, time, old_cc = 0;
      unsigned long flags, cr0, mask, dummy;
      int irq_context;

      irq_context = in_interrupt();
      if (!irq_context)
            local_bh_disable();
      local_irq_save(flags);
      if (raw_irqs_disabled_flags(flags)) {
            old_cc = local_tick_disable();
            S390_lowcore.clock_comparator = -1ULL;
            __ctl_store(cr0, 0, 0);
            dummy = (cr0 & 0xffff00e0) | 0x00000800;
            __ctl_load(dummy , 0, 0);
            mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT;
      } else
            mask = psw_kernel_bits | PSW_MASK_WAIT |
                  PSW_MASK_EXT | PSW_MASK_IO;

      end = get_clock() + ((u64) usecs << 12);
      do {
            time = end < S390_lowcore.clock_comparator ?
                  end : S390_lowcore.clock_comparator;
            set_clock_comparator(time);
            trace_hardirqs_on();
            __load_psw_mask(mask);
            local_irq_disable();
      } while (get_clock() < end);

      if (raw_irqs_disabled_flags(flags)) {
            __ctl_load(cr0, 0, 0);
            local_tick_enable(old_cc);
      }
      if (!irq_context)
            _local_bh_enable();
      set_clock_comparator(S390_lowcore.clock_comparator);
      local_irq_restore(flags);
}

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