linux/arch/s390/lib/delay.c
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   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/irqflags.h>
  13#include <linux/interrupt.h>
  14
  15void __delay(unsigned long loops)
  16{
  17        /*
  18         * To end the bloody studid and useless discussion about the
  19         * BogoMips number I took the liberty to define the __delay
  20         * function in a way that that resulting BogoMips number will
  21         * yield the megahertz number of the cpu. The important function
  22         * is udelay and that is done using the tod clock. -- martin.
  23         */
  24        asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
  25}
  26
  27static void __udelay_disabled(unsigned long usecs)
  28{
  29        unsigned long mask, cr0, cr0_saved;
  30        u64 clock_saved;
  31
  32        clock_saved = local_tick_disable();
  33        set_clock_comparator(get_clock() + ((u64) usecs << 12));
  34        __ctl_store(cr0_saved, 0, 0);
  35        cr0 = (cr0_saved & 0xffff00e0) | 0x00000800;
  36        __ctl_load(cr0 , 0, 0);
  37        mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT;
  38        trace_hardirqs_on();
  39        __load_psw_mask(mask);
  40        local_irq_disable();
  41        __ctl_load(cr0_saved, 0, 0);
  42        local_tick_enable(clock_saved);
  43        set_clock_comparator(S390_lowcore.clock_comparator);
  44}
  45
  46static void __udelay_enabled(unsigned long usecs)
  47{
  48        unsigned long mask;
  49        u64 end, time;
  50
  51        mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT | PSW_MASK_IO;
  52        end = get_clock() + ((u64) usecs << 12);
  53        do {
  54                time = end < S390_lowcore.clock_comparator ?
  55                        end : S390_lowcore.clock_comparator;
  56                set_clock_comparator(time);
  57                trace_hardirqs_on();
  58                __load_psw_mask(mask);
  59                local_irq_disable();
  60        } while (get_clock() < end);
  61        set_clock_comparator(S390_lowcore.clock_comparator);
  62}
  63
  64/*
  65 * Waits for 'usecs' microseconds using the TOD clock comparator.
  66 */
  67void __udelay(unsigned long usecs)
  68{
  69        unsigned long flags;
  70
  71        preempt_disable();
  72        local_irq_save(flags);
  73        if (in_irq()) {
  74                __udelay_disabled(usecs);
  75                goto out;
  76        }
  77        if (in_softirq()) {
  78                if (raw_irqs_disabled_flags(flags))
  79                        __udelay_disabled(usecs);
  80                else
  81                        __udelay_enabled(usecs);
  82                goto out;
  83        }
  84        if (raw_irqs_disabled_flags(flags)) {
  85                local_bh_disable();
  86                __udelay_disabled(usecs);
  87                _local_bh_enable();
  88                goto out;
  89        }
  90        __udelay_enabled(usecs);
  91out:
  92        local_irq_restore(flags);
  93        preempt_enable();
  94}
  95