1 /* 2 * linux/arch/arm/mach-footbridge/isa-timer.c 3 * 4 * Copyright (C) 1998 Russell King. 5 * Copyright (C) 1998 Phil Blundell 6 */ 7 #include <linux/clockchips.h> 8 #include <linux/clocksource.h> 9 #include <linux/init.h> 10 #include <linux/interrupt.h> 11 #include <linux/irq.h> 12 #include <linux/io.h> 13 #include <linux/timex.h> 14 15 #include <asm/irq.h> 16 17 #include <asm/mach/time.h> 18 19 #include "common.h" 20 21 #define PIT_MODE 0x43 22 #define PIT_CH0 0x40 23 24 #define PIT_LATCH ((PIT_TICK_RATE + HZ / 2) / HZ) 25 26 static cycle_t pit_read(struct clocksource *cs) 27 { 28 unsigned long flags; 29 static int old_count; 30 static u32 old_jifs; 31 int count; 32 u32 jifs; 33 34 raw_local_irq_save(flags); 35 36 jifs = jiffies; 37 outb_p(0x00, PIT_MODE); /* latch the count */ 38 count = inb_p(PIT_CH0); /* read the latched count */ 39 count |= inb_p(PIT_CH0) << 8; 40 41 if (count > old_count && jifs == old_jifs) 42 count = old_count; 43 44 old_count = count; 45 old_jifs = jifs; 46 47 raw_local_irq_restore(flags); 48 49 count = (PIT_LATCH - 1) - count; 50 51 return (cycle_t)(jifs * PIT_LATCH) + count; 52 } 53 54 static struct clocksource pit_cs = { 55 .name = "pit", 56 .rating = 110, 57 .read = pit_read, 58 .mask = CLOCKSOURCE_MASK(32), 59 }; 60 61 static void pit_set_mode(enum clock_event_mode mode, 62 struct clock_event_device *evt) 63 { 64 unsigned long flags; 65 66 raw_local_irq_save(flags); 67 68 switch (mode) { 69 case CLOCK_EVT_MODE_PERIODIC: 70 outb_p(0x34, PIT_MODE); 71 outb_p(PIT_LATCH & 0xff, PIT_CH0); 72 outb_p(PIT_LATCH >> 8, PIT_CH0); 73 break; 74 75 case CLOCK_EVT_MODE_SHUTDOWN: 76 case CLOCK_EVT_MODE_UNUSED: 77 outb_p(0x30, PIT_MODE); 78 outb_p(0, PIT_CH0); 79 outb_p(0, PIT_CH0); 80 break; 81 82 case CLOCK_EVT_MODE_ONESHOT: 83 case CLOCK_EVT_MODE_RESUME: 84 break; 85 } 86 local_irq_restore(flags); 87 } 88 89 static int pit_set_next_event(unsigned long delta, 90 struct clock_event_device *evt) 91 { 92 return 0; 93 } 94 95 static struct clock_event_device pit_ce = { 96 .name = "pit", 97 .features = CLOCK_EVT_FEAT_PERIODIC, 98 .set_mode = pit_set_mode, 99 .set_next_event = pit_set_next_event, 100 .shift = 32, 101 }; 102 103 static irqreturn_t pit_timer_interrupt(int irq, void *dev_id) 104 { 105 struct clock_event_device *ce = dev_id; 106 ce->event_handler(ce); 107 return IRQ_HANDLED; 108 } 109 110 static struct irqaction pit_timer_irq = { 111 .name = "pit", 112 .handler = pit_timer_interrupt, 113 .flags = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL, 114 .dev_id = &pit_ce, 115 }; 116 117 static void __init isa_timer_init(void) 118 { 119 pit_ce.cpumask = cpumask_of(smp_processor_id()); 120 pit_ce.mult = div_sc(PIT_TICK_RATE, NSEC_PER_SEC, pit_ce.shift); 121 pit_ce.max_delta_ns = clockevent_delta2ns(0x7fff, &pit_ce); 122 pit_ce.min_delta_ns = clockevent_delta2ns(0x000f, &pit_ce); 123 124 clocksource_register_hz(&pit_cs, PIT_TICK_RATE); 125 126 setup_irq(pit_ce.irq, &pit_timer_irq); 127 clockevents_register_device(&pit_ce); 128 } 129 130 struct sys_timer isa_timer = { 131 .init = isa_timer_init, 132 }; 133