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/*
* i8253.c 8253/PIT functions
*
*/
#include <linux/clockchips.h>
#include <linux/i8253.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/smp.h>
#include <linux/spinlock.h>
#include <linux/irq.h>
#include <asm/delay.h>
#include <asm/io.h>
#include <asm/time.h>
/*
* Initialize the PIT timer.
*
* This is also called after resume to bring the PIT into operation again.
*/
static void init_pit_timer(enum clock_event_mode mode,
struct clock_event_device *evt)
{
raw_spin_lock(&i8253_lock);
switch(mode) {
case CLOCK_EVT_MODE_PERIODIC:
/* binary, mode 2, LSB/MSB, ch 0 */
outb_p(0x34, PIT_MODE);
outb_p(LATCH & 0xff , PIT_CH0); /* LSB */
outb(LATCH >> 8 , PIT_CH0); /* MSB */
break;
case CLOCK_EVT_MODE_SHUTDOWN:
case CLOCK_EVT_MODE_UNUSED:
if (evt->mode == CLOCK_EVT_MODE_PERIODIC ||
evt->mode == CLOCK_EVT_MODE_ONESHOT) {
outb_p(0x30, PIT_MODE);
outb_p(0, PIT_CH0);
outb_p(0, PIT_CH0);
}
break;
case CLOCK_EVT_MODE_ONESHOT:
/* One shot setup */
outb_p(0x38, PIT_MODE);
break;
case CLOCK_EVT_MODE_RESUME:
/* Nothing to do here */
break;
}
raw_spin_unlock(&i8253_lock);
}
/*
* Program the next event in oneshot mode
*
* Delta is given in PIT ticks
*/
static int pit_next_event(unsigned long delta, struct clock_event_device *evt)
{
raw_spin_lock(&i8253_lock);
outb_p(delta & 0xff , PIT_CH0); /* LSB */
outb(delta >> 8 , PIT_CH0); /* MSB */
raw_spin_unlock(&i8253_lock);
return 0;
}
/*
* On UP the PIT can serve all of the possible timer functions. On SMP systems
* it can be solely used for the global tick.
*
* The profiling and update capabilites are switched off once the local apic is
* registered. This mechanism replaces the previous #ifdef LOCAL_APIC -
* !using_apic_timer decisions in do_timer_interrupt_hook()
*/
static struct clock_event_device pit_clockevent = {
.name = "pit",
.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
.set_mode = init_pit_timer,
.set_next_event = pit_next_event,
.irq = 0,
};
static irqreturn_t timer_interrupt(int irq, void *dev_id)
{
pit_clockevent.event_handler(&pit_clockevent);
return IRQ_HANDLED;
}
static struct irqaction irq0 = {
.handler = timer_interrupt,
.flags = IRQF_DISABLED | IRQF_NOBALANCING | IRQF_TIMER,
.name = "timer"
};
/*
* Initialize the conversion factor and the min/max deltas of the clock event
* structure and register the clock event source with the framework.
*/
void __init setup_pit_timer(void)
{
struct clock_event_device *cd = &pit_clockevent;
unsigned int cpu = smp_processor_id();
/*
* Start pit with the boot cpu mask and make it global after the
* IO_APIC has been initialized.
*/
cd->cpumask = cpumask_of(cpu);
clockevent_set_clock(cd, CLOCK_TICK_RATE);
cd->max_delta_ns = clockevent_delta2ns(0x7FFF, cd);
cd->min_delta_ns = clockevent_delta2ns(0xF, cd);
clockevents_register_device(cd);
setup_irq(0, &irq0);
}
static int __init init_pit_clocksource(void)
{
if (num_possible_cpus() > 1) /* PIT does not scale! */
return 0;
return clocksource_i8253_init();
}
arch_initcall(init_pit_clocksource);
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