61ee9a4ba0
Let the core do the work. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: John Stultz <john.stultz@linaro.org> Reviewed-by: Ingo Molnar <mingo@elte.hu> Link: http://lkml.kernel.org/r/%3C20110518210136.545615675%40linutronix.de%3E
133 lines
3.2 KiB
C
133 lines
3.2 KiB
C
/*
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* 8253/PIT functions
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*
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*/
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#include <linux/clockchips.h>
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#include <linux/interrupt.h>
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#include <linux/spinlock.h>
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#include <linux/jiffies.h>
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#include <linux/module.h>
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#include <linux/timex.h>
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#include <linux/delay.h>
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#include <linux/init.h>
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#include <linux/io.h>
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#include <asm/i8253.h>
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#include <asm/hpet.h>
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#include <asm/smp.h>
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DEFINE_RAW_SPINLOCK(i8253_lock);
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EXPORT_SYMBOL(i8253_lock);
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/*
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* HPET replaces the PIT, when enabled. So we need to know, which of
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* the two timers is used
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*/
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struct clock_event_device *global_clock_event;
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/*
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* Initialize the PIT timer.
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*
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* This is also called after resume to bring the PIT into operation again.
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*/
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static void init_pit_timer(enum clock_event_mode mode,
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struct clock_event_device *evt)
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{
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raw_spin_lock(&i8253_lock);
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switch (mode) {
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case CLOCK_EVT_MODE_PERIODIC:
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/* binary, mode 2, LSB/MSB, ch 0 */
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outb_pit(0x34, PIT_MODE);
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outb_pit(LATCH & 0xff , PIT_CH0); /* LSB */
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outb_pit(LATCH >> 8 , PIT_CH0); /* MSB */
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break;
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case CLOCK_EVT_MODE_SHUTDOWN:
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case CLOCK_EVT_MODE_UNUSED:
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if (evt->mode == CLOCK_EVT_MODE_PERIODIC ||
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evt->mode == CLOCK_EVT_MODE_ONESHOT) {
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outb_pit(0x30, PIT_MODE);
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outb_pit(0, PIT_CH0);
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outb_pit(0, PIT_CH0);
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}
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break;
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case CLOCK_EVT_MODE_ONESHOT:
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/* One shot setup */
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outb_pit(0x38, PIT_MODE);
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break;
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case CLOCK_EVT_MODE_RESUME:
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/* Nothing to do here */
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break;
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}
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raw_spin_unlock(&i8253_lock);
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}
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/*
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* Program the next event in oneshot mode
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*
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* Delta is given in PIT ticks
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*/
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static int pit_next_event(unsigned long delta, struct clock_event_device *evt)
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{
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raw_spin_lock(&i8253_lock);
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outb_pit(delta & 0xff , PIT_CH0); /* LSB */
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outb_pit(delta >> 8 , PIT_CH0); /* MSB */
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raw_spin_unlock(&i8253_lock);
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return 0;
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}
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/*
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* On UP the PIT can serve all of the possible timer functions. On SMP systems
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* it can be solely used for the global tick.
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*
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* The profiling and update capabilities are switched off once the local apic is
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* registered. This mechanism replaces the previous #ifdef LOCAL_APIC -
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* !using_apic_timer decisions in do_timer_interrupt_hook()
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*/
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static struct clock_event_device pit_ce = {
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.name = "pit",
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.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
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.set_mode = init_pit_timer,
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.set_next_event = pit_next_event,
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.irq = 0,
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};
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/*
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* Initialize the conversion factor and the min/max deltas of the clock event
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* structure and register the clock event source with the framework.
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*/
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void __init setup_pit_timer(void)
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{
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/*
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* Start pit with the boot cpu mask and make it global after the
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* IO_APIC has been initialized.
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*/
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pit_ce.cpumask = cpumask_of(smp_processor_id());
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clockevents_config_and_register(&pit_ce, CLOCK_TICK_RATE, 0xF, 0x7FFF);
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global_clock_event = &pit_ce;
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}
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#ifndef CONFIG_X86_64
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static int __init init_pit_clocksource(void)
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{
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/*
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* Several reasons not to register PIT as a clocksource:
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*
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* - On SMP PIT does not scale due to i8253_lock
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* - when HPET is enabled
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* - when local APIC timer is active (PIT is switched off)
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*/
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if (num_possible_cpus() > 1 || is_hpet_enabled() ||
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pit_ce.mode != CLOCK_EVT_MODE_PERIODIC)
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return 0;
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return clocksource_i8253_init();
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}
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arch_initcall(init_pit_clocksource);
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#endif /* !CONFIG_X86_64 */
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