arch/arm/mach-footbridge/isa-timer.c

   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 };