delay.c

Go to the documentation of this file.

/*
 *    Precise Delay Loops for S390
 *
 *    Copyright IBM Corp. 1999, 2008
 *    Author(s): Martin Schwidefsky <[email protected]>,
 *       Heiko Carstens <[email protected]>,
 */

#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/timex.h>
#include <linux/module.h>
#include <linux/irqflags.h>
#include <linux/interrupt.h>
#include <asm/vtimer.h>
#include <asm/div64.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 long usecs)
{
    unsigned long cr0, cr6, new;
    u64 clock_saved, end;

    end = get_clock() + (usecs << 12);
    clock_saved = local_tick_disable();
    __ctl_store(cr0, 0, 0);
    __ctl_store(cr6, 6, 6);
    new = (cr0 &  0xffff00e0) | 0x00000800;
    __ctl_load(new , 0, 0);
    new = 0;
    __ctl_load(new, 6, 6);
    lockdep_off();
    do {
        set_clock_comparator(end);
        vtime_stop_cpu();
        local_irq_disable();
    } while (get_clock() < end);
    lockdep_on();
    __ctl_load(cr0, 0, 0);
    __ctl_load(cr6, 6, 6);
    local_tick_enable(clock_saved);
}

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

    end = get_clock() + (usecs << 12);
    do {
        clock_saved = 0;
        if (end < S390_lowcore.clock_comparator) {
            clock_saved = local_tick_disable();
            set_clock_comparator(end);
        }
        vtime_stop_cpu();
        local_irq_disable();
        if (clock_saved)
            local_tick_enable(clock_saved);
    } while (get_clock() < end);
}

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

/*
 * Simple udelay variant. To be used on startup and reboot
 * when the interrupt handler isn't working.
 */
void udelay_simple(unsigned long long usecs)
{
    u64 end;

    end = get_clock() + (usecs << 12);
    while (get_clock() < end)
        cpu_relax();
}

void __ndelay(unsigned long long nsecs)
{
    u64 end;

    nsecs <<= 9;
    do_div(nsecs, 125);
    end = get_clock() + nsecs;
    if (nsecs & ~0xfffUL)
        __udelay(nsecs >> 12);
    while (get_clock() < end)
        barrier();
}
EXPORT_SYMBOL(__ndelay);