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/export.h>
  13#include <linux/irqflags.h>
  14#include <linux/interrupt.h>
  15#include <linux/irq.h>
  16#include <asm/vtimer.h>
  17#include <asm/div64.h>
  18#include <asm/idle.h>
  19
  20void __delay(unsigned long loops)
  21{
  22        /*
  23         * To end the bloody studid and useless discussion about the
  24         * BogoMips number I took the liberty to define the __delay
  25         * function in a way that that resulting BogoMips number will
  26         * yield the megahertz number of the cpu. The important function
  27         * is udelay and that is done using the tod clock. -- martin.
  28         */
  29        asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
  30}
  31EXPORT_SYMBOL(__delay);
  32
  33static void __udelay_disabled(unsigned long long usecs)
  34{
  35        unsigned long cr0, cr0_new, psw_mask;
  36        struct s390_idle_data idle;
  37        u64 end;
  38
  39        end = get_tod_clock() + (usecs << 12);
  40        __ctl_store(cr0, 0, 0);
  41        cr0_new = cr0 & ~CR0_IRQ_SUBCLASS_MASK;
  42        cr0_new |= (1UL << (63 - 52)); /* enable clock comparator irq */
  43        __ctl_load(cr0_new, 0, 0);
  44        psw_mask = __extract_psw() | PSW_MASK_EXT | PSW_MASK_WAIT;
  45        set_clock_comparator(end);
  46        set_cpu_flag(CIF_IGNORE_IRQ);
  47        psw_idle(&idle, psw_mask);
  48        clear_cpu_flag(CIF_IGNORE_IRQ);
  49        set_clock_comparator(S390_lowcore.clock_comparator);
  50        __ctl_load(cr0, 0, 0);
  51}
  52
  53static void __udelay_enabled(unsigned long long usecs)
  54{
  55        u64 clock_saved, end;
  56
  57        end = get_tod_clock_fast() + (usecs << 12);
  58        do {
  59                clock_saved = 0;
  60                if (end < S390_lowcore.clock_comparator) {
  61                        clock_saved = local_tick_disable();
  62                        set_clock_comparator(end);
  63                }
  64                enabled_wait();
  65                if (clock_saved)
  66                        local_tick_enable(clock_saved);
  67        } while (get_tod_clock_fast() < end);
  68}
  69
  70/*
  71 * Waits for 'usecs' microseconds using the TOD clock comparator.
  72 */
  73void __udelay(unsigned long long usecs)
  74{
  75        unsigned long flags;
  76
  77        preempt_disable();
  78        local_irq_save(flags);
  79        if (in_irq()) {
  80                __udelay_disabled(usecs);
  81                goto out;
  82        }
  83        if (in_softirq()) {
  84                if (raw_irqs_disabled_flags(flags))
  85                        __udelay_disabled(usecs);
  86                else
  87                        __udelay_enabled(usecs);
  88                goto out;
  89        }
  90        if (raw_irqs_disabled_flags(flags)) {
  91                local_bh_disable();
  92                __udelay_disabled(usecs);
  93                _local_bh_enable();
  94                goto out;
  95        }
  96        __udelay_enabled(usecs);
  97out:
  98        local_irq_restore(flags);
  99        preempt_enable();
 100}
 101EXPORT_SYMBOL(__udelay);
 102
 103/*
 104 * Simple udelay variant. To be used on startup and reboot
 105 * when the interrupt handler isn't working.
 106 */
 107void udelay_simple(unsigned long long usecs)
 108{
 109        u64 end;
 110
 111        end = get_tod_clock_fast() + (usecs << 12);
 112        while (get_tod_clock_fast() < end)
 113                cpu_relax();
 114}
 115
 116void __ndelay(unsigned long long nsecs)
 117{
 118        u64 end;
 119
 120        nsecs <<= 9;
 121        do_div(nsecs, 125);
 122        end = get_tod_clock_fast() + nsecs;
 123        if (nsecs & ~0xfffUL)
 124                __udelay(nsecs >> 12);
 125        while (get_tod_clock_fast() < end)
 126                barrier();
 127}
 128EXPORT_SYMBOL(__ndelay);
 129