arch/avr32/kernel/time.c

   1 /*
   2  * Copyright (C) 2004-2007 Atmel Corporation
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8 #include <linux/clk.h>
   9 #include <linux/clockchips.h>
  10 #include <linux/init.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/irq.h>
  13 #include <linux/kernel.h>
  14 #include <linux/time.h>
  15
  16 #include <asm/sysreg.h>
  17
  18 #include <mach/pm.h>
  19
  20
  21 static cycle_t read_cycle_count(struct clocksource *cs)
  22 {
  23         return (cycle_t)sysreg_read(COUNT);
  24 }
  25
  26 /*
  27  * The architectural cycle count registers are a fine clocksource unless
  28  * the system idle loop use sleep states like "idle":  the CPU cycles
  29  * measured by COUNT (and COMPARE) don't happen during sleep states.
  30  * Their duration also changes if cpufreq changes the CPU clock rate.
  31  * So we rate the clocksource using COUNT as very low quality.
  32  */
  33 static struct clocksource counter = {
  34         .name           = "avr32_counter",
  35         .rating         = 50,
  36         .read           = read_cycle_count,
  37         .mask           = CLOCKSOURCE_MASK(32),
  38         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  39 };
  40
  41 static irqreturn_t timer_interrupt(int irq, void *dev_id)
  42 {
  43         struct clock_event_device *evdev = dev_id;
  44
  45         if (unlikely(!(intc_get_pending(0) & 1)))
  46                 return IRQ_NONE;
  47
  48         /*
  49          * Disable the interrupt until the clockevent subsystem
  50          * reprograms it.
  51          */
  52         sysreg_write(COMPARE, 0);
  53
  54         evdev->event_handler(evdev);
  55         return IRQ_HANDLED;
  56 }
  57
  58 static struct irqaction timer_irqaction = {
  59         .handler        = timer_interrupt,
  60         /* Oprofile uses the same irq as the timer, so allow it to be shared */
  61         .flags          = IRQF_TIMER | IRQF_DISABLED | IRQF_SHARED,
  62         .name           = "avr32_comparator",
  63 };
  64
  65 static int comparator_next_event(unsigned long delta,
  66                 struct clock_event_device *evdev)
  67 {
  68         unsigned long   flags;
  69
  70         raw_local_irq_save(flags);
  71
  72         /* The time to read COUNT then update COMPARE must be less
  73          * than the min_delta_ns value for this clockevent source.
  74          */
  75         sysreg_write(COMPARE, (sysreg_read(COUNT) + delta) ? : 1);
  76
  77         raw_local_irq_restore(flags);
  78
  79         return 0;
  80 }
  81
  82 static void comparator_mode(enum clock_event_mode mode,
  83                 struct clock_event_device *evdev)
  84 {
  85         switch (mode) {
  86         case CLOCK_EVT_MODE_ONESHOT:
  87                 pr_debug("%s: start\n", evdev->name);
  88                 /* FALLTHROUGH */
  89         case CLOCK_EVT_MODE_RESUME:
  90                 cpu_disable_idle_sleep();
  91                 break;
  92         case CLOCK_EVT_MODE_UNUSED:
  93         case CLOCK_EVT_MODE_SHUTDOWN:
  94                 sysreg_write(COMPARE, 0);
  95                 pr_debug("%s: stop\n", evdev->name);
  96                 cpu_enable_idle_sleep();
  97                 break;
  98         default:
  99                 BUG();
 100         }
 101 }
 102
 103 static struct clock_event_device comparator = {
 104         .name           = "avr32_comparator",
 105         .features       = CLOCK_EVT_FEAT_ONESHOT,
 106         .shift          = 16,
 107         .rating         = 50,
 108         .set_next_event = comparator_next_event,
 109         .set_mode       = comparator_mode,
 110 };
 111
 112 void read_persistent_clock(struct timespec *ts)
 113 {
 114         ts->tv_sec = mktime(2007, 1, 1, 0, 0, 0);
 115         ts->tv_nsec = 0;
 116 }
 117
 118 void __init time_init(void)
 119 {
 120         unsigned long counter_hz;
 121         int ret;
 122
 123         /* figure rate for counter */
 124         counter_hz = clk_get_rate(boot_cpu_data.clk);
 125         ret = clocksource_register_hz(&counter, counter_hz);
 126         if (ret)
 127                 pr_debug("timer: could not register clocksource: %d\n", ret);
 128
 129         /* setup COMPARE clockevent */
 130         comparator.mult = div_sc(counter_hz, NSEC_PER_SEC, comparator.shift);
 131         comparator.max_delta_ns = clockevent_delta2ns((u32)~0, &comparator);
 132         comparator.min_delta_ns = clockevent_delta2ns(50, &comparator) + 1;
 133         comparator.cpumask = cpumask_of(0);
 134
 135         sysreg_write(COMPARE, 0);
 136         timer_irqaction.dev_id = &comparator;
 137
 138         ret = setup_irq(0, &timer_irqaction);
 139         if (ret)
 140                 pr_debug("timer: could not request IRQ 0: %d\n", ret);
 141         else {
 142                 clockevents_register_device(&comparator);
 143
 144                 pr_info("%s: irq 0, %lu.%03lu MHz\n", comparator.name,
 145                                 ((counter_hz + 500) / 1000) / 1000,
 146                                 ((counter_hz + 500) / 1000) % 1000);
 147         }
 148 }