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delay.c

/*
 *    Precise Delay Loops for S390
 *
 *    Copyright IBM Corp. 1999,2008
 *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
 *           Heiko Carstens <heiko.carstens@de.ibm.com>,
 */

#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));
}

static void __udelay_disabled(unsigned long usecs)
{
      unsigned long mask, cr0, cr0_saved;
      u64 clock_saved;

      clock_saved = local_tick_disable();
      set_clock_comparator(get_clock() + ((u64) usecs << 12));
      __ctl_store(cr0_saved, 0, 0);
      cr0 = (cr0_saved & 0xffff00e0) | 0x00000800;
      __ctl_load(cr0 , 0, 0);
      mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT;
      trace_hardirqs_on();
      __load_psw_mask(mask);
      local_irq_disable();
      __ctl_load(cr0_saved, 0, 0);
      local_tick_enable(clock_saved);
      set_clock_comparator(S390_lowcore.clock_comparator);
}

static void __udelay_enabled(unsigned long usecs)
{
      unsigned long mask;
      u64 end, time;

      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);
      set_clock_comparator(S390_lowcore.clock_comparator);
}

/*
 * Waits for 'usecs' microseconds using the TOD clock comparator.
 */
void __udelay(unsigned long usecs)
{
      unsigned long flags;

      preempt_disable();
      local_irq_save(flags);
      if (in_irq()) {
            __udelay_disabled(usecs);
            goto out;
      }
      if (in_softirq()) {
            if (raw_irqs_disabled_flags(flags))
                  __udelay_disabled(usecs);
            else
                  __udelay_enabled(usecs);
            goto out;
      }
      if (raw_irqs_disabled_flags(flags)) {
            local_bh_disable();
            __udelay_disabled(usecs);
            _local_bh_enable();
            goto out;
      }
      __udelay_enabled(usecs);
out:
      local_irq_restore(flags);
      preempt_enable();
}

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