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/time.h>
  11 #include <linux/module.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/irq.h>
  14 #include <linux/kernel_stat.h>
  15 #include <linux/errno.h>
  16 #include <linux/init.h>
  17 #include <linux/profile.h>
  18 #include <linux/sysdev.h>
  19 #include <linux/err.h>
  20
  21 #include <asm/div64.h>
  22 #include <asm/sysreg.h>
  23 #include <asm/io.h>
  24 #include <asm/sections.h>
  25
  26 #include <asm/arch/pm.h>
  27
  28
  29 static cycle_t read_cycle_count(void)
  30 {
  31         return (cycle_t)sysreg_read(COUNT);
  32 }
  33
  34 /*
  35  * The architectural cycle count registers are a fine clocksource unless
  36  * the system idle loop use sleep states like "idle":  the CPU cycles
  37  * measured by COUNT (and COMPARE) don't happen during sleep states.
  38  * Their duration also changes if cpufreq changes the CPU clock rate.
  39  * So we rate the clocksource using COUNT as very low quality.
  40  */
  41 static struct clocksource counter = {
  42         .name           = "avr32_counter",
  43         .rating         = 50,
  44         .read           = read_cycle_count,
  45         .mask           = CLOCKSOURCE_MASK(32),
  46         .shift          = 16,
  47         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  48 };
  49
  50 static irqreturn_t timer_interrupt(int irq, void *dev_id)
  51 {
  52         struct clock_event_device *evdev = dev_id;
  53
  54         /*
  55          * Disable the interrupt until the clockevent subsystem
  56          * reprograms it.
  57          */
  58         sysreg_write(COMPARE, 0);
  59
  60         evdev->event_handler(evdev);
  61         return IRQ_HANDLED;
  62 }
  63
  64 static struct irqaction timer_irqaction = {
  65         .handler        = timer_interrupt,
  66         .flags          = IRQF_TIMER | IRQF_DISABLED,
  67         .name           = "avr32_comparator",
  68 };
  69
  70 static int comparator_next_event(unsigned long delta,
  71                 struct clock_event_device *evdev)
  72 {
  73         unsigned long   flags;
  74
  75         raw_local_irq_save(flags);
  76
  77         /* The time to read COUNT then update COMPARE must be less
  78          * than the min_delta_ns value for this clockevent source.
  79          */
  80         sysreg_write(COMPARE, (sysreg_read(COUNT) + delta) ? : 1);
  81
  82         raw_local_irq_restore(flags);
  83
  84         return 0;
  85 }
  86
  87 static void comparator_mode(enum clock_event_mode mode,
  88                 struct clock_event_device *evdev)
  89 {
  90         switch (mode) {
  91         case CLOCK_EVT_MODE_ONESHOT:
  92                 pr_debug("%s: start\n", evdev->name);
  93                 /* FALLTHROUGH */
  94         case CLOCK_EVT_MODE_RESUME:
  95                 cpu_disable_idle_sleep();
  96                 break;
  97         case CLOCK_EVT_MODE_UNUSED:
  98         case CLOCK_EVT_MODE_SHUTDOWN:
  99                 sysreg_write(COMPARE, 0);
 100                 pr_debug("%s: stop\n", evdev->name);
 101                 cpu_enable_idle_sleep();
 102                 break;
 103         default:
 104                 BUG();
 105         }
 106 }
 107
 108 static struct clock_event_device comparator = {
 109         .name           = "avr32_comparator",
 110         .features       = CLOCK_EVT_FEAT_ONESHOT,
 111         .shift          = 16,
 112         .rating         = 50,
 113         .cpumask        = CPU_MASK_CPU0,
 114         .set_next_event = comparator_next_event,
 115         .set_mode       = comparator_mode,
 116 };
 117
 118 void __init time_init(void)
 119 {
 120         unsigned long counter_hz;
 121         int ret;
 122
 123         xtime.tv_sec = mktime(2007, 1, 1, 0, 0, 0);
 124         xtime.tv_nsec = 0;
 125
 126         set_normalized_timespec(&wall_to_monotonic,
 127                                 -xtime.tv_sec, -xtime.tv_nsec);
 128
 129         /* figure rate for counter */
 130         counter_hz = clk_get_rate(boot_cpu_data.clk);
 131         counter.mult = clocksource_hz2mult(counter_hz, counter.shift);
 132
 133         ret = clocksource_register(&counter);
 134         if (ret)
 135                 pr_debug("timer: could not register clocksource: %d\n", ret);
 136
 137         /* setup COMPARE clockevent */
 138         comparator.mult = div_sc(counter_hz, NSEC_PER_SEC, comparator.shift);
 139         comparator.max_delta_ns = clockevent_delta2ns((u32)~0, &comparator);
 140         comparator.min_delta_ns = clockevent_delta2ns(50, &comparator) + 1;
 141
 142         sysreg_write(COMPARE, 0);
 143         timer_irqaction.dev_id = &comparator;
 144
 145         ret = setup_irq(0, &timer_irqaction);
 146         if (ret)
 147                 pr_debug("timer: could not request IRQ 0: %d\n", ret);
 148         else {
 149                 clockevents_register_device(&comparator);
 150
 151                 pr_info("%s: irq 0, %lu.%03lu MHz\n", comparator.name,
 152                                 ((counter_hz + 500) / 1000) / 1000,
 153                                 ((counter_hz + 500) / 1000) % 1000);
 154         }
 155 }