1 /* 2 * i8253.c 8253/PIT functions 3 * 4 */ 5 #include <linux/clockchips.h> 6 #include <linux/init.h> 7 #include <linux/interrupt.h> 8 #include <linux/jiffies.h> 9 #include <linux/module.h> 10 #include <linux/smp.h> 11 #include <linux/spinlock.h> 12 #include <linux/irq.h> 13 14 #include <asm/delay.h> 15 #include <asm/i8253.h> 16 #include <asm/io.h> 17 #include <asm/time.h> 18 19 DEFINE_RAW_SPINLOCK(i8253_lock); 20 EXPORT_SYMBOL(i8253_lock); 21 22 /* 23 * Initialize the PIT timer. 24 * 25 * This is also called after resume to bring the PIT into operation again. 26 */ 27 static void init_pit_timer(enum clock_event_mode mode, 28 struct clock_event_device *evt) 29 { 30 raw_spin_lock(&i8253_lock); 31 32 switch(mode) { 33 case CLOCK_EVT_MODE_PERIODIC: 34 /* binary, mode 2, LSB/MSB, ch 0 */ 35 outb_p(0x34, PIT_MODE); 36 outb_p(LATCH & 0xff , PIT_CH0); /* LSB */ 37 outb(LATCH >> 8 , PIT_CH0); /* MSB */ 38 break; 39 40 case CLOCK_EVT_MODE_SHUTDOWN: 41 case CLOCK_EVT_MODE_UNUSED: 42 if (evt->mode == CLOCK_EVT_MODE_PERIODIC || 43 evt->mode == CLOCK_EVT_MODE_ONESHOT) { 44 outb_p(0x30, PIT_MODE); 45 outb_p(0, PIT_CH0); 46 outb_p(0, PIT_CH0); 47 } 48 break; 49 50 case CLOCK_EVT_MODE_ONESHOT: 51 /* One shot setup */ 52 outb_p(0x38, PIT_MODE); 53 break; 54 55 case CLOCK_EVT_MODE_RESUME: 56 /* Nothing to do here */ 57 break; 58 } 59 raw_spin_unlock(&i8253_lock); 60 } 61 62 /* 63 * Program the next event in oneshot mode 64 * 65 * Delta is given in PIT ticks 66 */ 67 static int pit_next_event(unsigned long delta, struct clock_event_device *evt) 68 { 69 raw_spin_lock(&i8253_lock); 70 outb_p(delta & 0xff , PIT_CH0); /* LSB */ 71 outb(delta >> 8 , PIT_CH0); /* MSB */ 72 raw_spin_unlock(&i8253_lock); 73 74 return 0; 75 } 76 77 /* 78 * On UP the PIT can serve all of the possible timer functions. On SMP systems 79 * it can be solely used for the global tick. 80 * 81 * The profiling and update capabilites are switched off once the local apic is 82 * registered. This mechanism replaces the previous #ifdef LOCAL_APIC - 83 * !using_apic_timer decisions in do_timer_interrupt_hook() 84 */ 85 static struct clock_event_device pit_clockevent = { 86 .name = "pit", 87 .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT, 88 .set_mode = init_pit_timer, 89 .set_next_event = pit_next_event, 90 .irq = 0, 91 }; 92 93 static irqreturn_t timer_interrupt(int irq, void *dev_id) 94 { 95 pit_clockevent.event_handler(&pit_clockevent); 96 97 return IRQ_HANDLED; 98 } 99 100 static struct irqaction irq0 = { 101 .handler = timer_interrupt, 102 .flags = IRQF_DISABLED | IRQF_NOBALANCING | IRQF_TIMER, 103 .name = "timer" 104 }; 105 106 /* 107 * Initialize the conversion factor and the min/max deltas of the clock event 108 * structure and register the clock event source with the framework. 109 */ 110 void __init setup_pit_timer(void) 111 { 112 struct clock_event_device *cd = &pit_clockevent; 113 unsigned int cpu = smp_processor_id(); 114 115 /* 116 * Start pit with the boot cpu mask and make it global after the 117 * IO_APIC has been initialized. 118 */ 119 cd->cpumask = cpumask_of(cpu); 120 clockevent_set_clock(cd, CLOCK_TICK_RATE); 121 cd->max_delta_ns = clockevent_delta2ns(0x7FFF, cd); 122 cd->min_delta_ns = clockevent_delta2ns(0xF, cd); 123 clockevents_register_device(cd); 124 125 setup_irq(0, &irq0); 126 } 127 128 static int __init init_pit_clocksource(void) 129 { 130 if (num_possible_cpus() > 1) /* PIT does not scale! */ 131 return 0; 132 133 return clocksource_i8253_init(); 134 } 135 arch_initcall(init_pit_clocksource); 136