LXR linux/arch/s390/lib/delay.c

   1/*
   2 *    Precise Delay Loops for S390
   3 *
   4 *    Copyright IBM Corp. 1999, 2008
   5 *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
   6 *               Heiko Carstens <heiko.carstens@de.ibm.com>,
   7 */
   8
   9#include <linux/sched.h>
  10#include <linux/delay.h>
  11#include <linux/timex.h>
  12#include <linux/module.h>
  13#include <linux/irqflags.h>
  14#include <linux/interrupt.h>
  15#include <asm/vtimer.h>
  16#include <asm/div64.h>
  17
  18void __delay(unsigned long loops)
  19{
  20        /*
  21         * To end the bloody studid and useless discussion about the
  22         * BogoMips number I took the liberty to define the __delay
  23         * function in a way that that resulting BogoMips number will
  24         * yield the megahertz number of the cpu. The important function
  25         * is udelay and that is done using the tod clock. -- martin.
  26         */
  27        asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
  28}
  29
  30static void __udelay_disabled(unsigned long long usecs)
  31{
  32        unsigned long cr0, cr6, new;
  33        u64 clock_saved, end;
  34
  35        end = get_tod_clock() + (usecs << 12);
  36        clock_saved = local_tick_disable();
  37        __ctl_store(cr0, 0, 0);
  38        __ctl_store(cr6, 6, 6);
  39        new = (cr0 &  0xffff00e0) | 0x00000800;
  40        __ctl_load(new , 0, 0);
  41        new = 0;
  42        __ctl_load(new, 6, 6);
  43        lockdep_off();
  44        do {
  45                set_clock_comparator(end);
  46                vtime_stop_cpu();
  47        } while (get_tod_clock_fast() < end);
  48        lockdep_on();
  49        __ctl_load(cr0, 0, 0);
  50        __ctl_load(cr6, 6, 6);
  51        local_tick_enable(clock_saved);
  52}
  53
  54static void __udelay_enabled(unsigned long long usecs)
  55{
  56        u64 clock_saved, end;
  57
  58        end = get_tod_clock_fast() + (usecs << 12);
  59        do {
  60                clock_saved = 0;
  61                if (end < S390_lowcore.clock_comparator) {
  62                        clock_saved = local_tick_disable();
  63                        set_clock_comparator(end);
  64                }
  65                vtime_stop_cpu();
  66                if (clock_saved)
  67                        local_tick_enable(clock_saved);
  68        } while (get_tod_clock_fast() < end);
  69}
  70
  71/*
  72 * Waits for 'usecs' microseconds using the TOD clock comparator.
  73 */
  74void __udelay(unsigned long long usecs)
  75{
  76        unsigned long flags;
  77
  78        preempt_disable();
  79        local_irq_save(flags);
  80        if (in_irq()) {
  81                __udelay_disabled(usecs);
  82                goto out;
  83        }
  84        if (in_softirq()) {
  85                if (raw_irqs_disabled_flags(flags))
  86                        __udelay_disabled(usecs);
  87                else
  88                        __udelay_enabled(usecs);
  89                goto out;
  90        }
  91        if (raw_irqs_disabled_flags(flags)) {
  92                local_bh_disable();
  93                __udelay_disabled(usecs);
  94                _local_bh_enable();
  95                goto out;
  96        }
  97        __udelay_enabled(usecs);
  98out:
  99        local_irq_restore(flags);
 100        preempt_enable();
 101}
 102EXPORT_SYMBOL(__udelay);
 103
 104/*
 105 * Simple udelay variant. To be used on startup and reboot
 106 * when the interrupt handler isn't working.
 107 */
 108void udelay_simple(unsigned long long usecs)
 109{
 110        u64 end;
 111
 112        end = get_tod_clock_fast() + (usecs << 12);
 113        while (get_tod_clock_fast() < end)
 114                cpu_relax();
 115}
 116EXPORT_SYMBOL(udelay_simple);
 117
 118void __ndelay(unsigned long long nsecs)
 119{
 120        u64 end;
 121
 122        nsecs <<= 9;
 123        do_div(nsecs, 125);
 124        end = get_tod_clock_fast() + nsecs;
 125        if (nsecs & ~0xfffUL)
 126                __udelay(nsecs >> 12);
 127        while (get_tod_clock_fast() < end)
 128                barrier();
 129}
 130EXPORT_SYMBOL(__ndelay);
 131