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

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *    Precise Delay Loops for S390
   4 *
   5 *    Copyright IBM Corp. 1999, 2008
   6 *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
   7 *               Heiko Carstens <heiko.carstens@de.ibm.com>,
   8 */
   9
  10#include <linux/sched.h>
  11#include <linux/delay.h>
  12#include <linux/timex.h>
  13#include <linux/export.h>
  14#include <linux/irqflags.h>
  15#include <linux/interrupt.h>
  16#include <linux/irq.h>
  17#include <asm/vtimer.h>
  18#include <asm/div64.h>
  19#include <asm/idle.h>
  20
  21void __delay(unsigned long loops)
  22{
  23        /*
  24         * To end the bloody studid and useless discussion about the
  25         * BogoMips number I took the liberty to define the __delay
  26         * function in a way that that resulting BogoMips number will
  27         * yield the megahertz number of the cpu. The important function
  28         * is udelay and that is done using the tod clock. -- martin.
  29         */
  30        asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
  31}
  32EXPORT_SYMBOL(__delay);
  33
  34static void __udelay_disabled(unsigned long long usecs)
  35{
  36        unsigned long cr0, cr0_new, psw_mask;
  37        struct s390_idle_data idle;
  38        u64 end;
  39
  40        end = get_tod_clock() + (usecs << 12);
  41        __ctl_store(cr0, 0, 0);
  42        cr0_new = cr0 & ~CR0_IRQ_SUBCLASS_MASK;
  43        cr0_new |= (1UL << (63 - 52)); /* enable clock comparator irq */
  44        __ctl_load(cr0_new, 0, 0);
  45        psw_mask = __extract_psw() | PSW_MASK_EXT | PSW_MASK_WAIT;
  46        set_clock_comparator(end);
  47        set_cpu_flag(CIF_IGNORE_IRQ);
  48        psw_idle(&idle, psw_mask);
  49        clear_cpu_flag(CIF_IGNORE_IRQ);
  50        set_clock_comparator(S390_lowcore.clock_comparator);
  51        __ctl_load(cr0, 0, 0);
  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 (tod_after(S390_lowcore.clock_comparator, end)) {
  62                        clock_saved = local_tick_disable();
  63                        set_clock_comparator(end);
  64                }
  65                enabled_wait();
  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}
 116
 117void __ndelay(unsigned long long nsecs)
 118{
 119        u64 end;
 120
 121        nsecs <<= 9;
 122        do_div(nsecs, 125);
 123        end = get_tod_clock_fast() + nsecs;
 124        if (nsecs & ~0xfffUL)
 125                __udelay(nsecs >> 12);
 126        while (get_tod_clock_fast() < end)
 127                barrier();
 128}
 129EXPORT_SYMBOL(__ndelay);
 130