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 <asm/arch/pm.h>
  19
  20
  21 static cycle_t read_cycle_count(void)
  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         .shift          = 16,
  39         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  40 };
  41
  42 static irqreturn_t timer_interrupt(int irq, void *dev_id)
  43 {
  44         struct clock_event_device *evdev = dev_id;
  45
  46         /*
  47          * Disable the interrupt until the clockevent subsystem
  48          * reprograms it.
  49          */
  50         sysreg_write(COMPARE, 0);
  51
  52         evdev->event_handler(evdev);
  53         return IRQ_HANDLED;
  54 }
  55
  56 static struct irqaction timer_irqaction = {
  57         .handler        = timer_interrupt,
  58         .flags          = IRQF_TIMER | IRQF_DISABLED,
  59         .name           = "avr32_comparator",
  60 };
  61
  62 static int comparator_next_event(unsigned long delta,
  63                 struct clock_event_device *evdev)
  64 {
  65         unsigned long   flags;
  66
  67         raw_local_irq_save(flags);
  68
  69         /* The time to read COUNT then update COMPARE must be less
  70          * than the min_delta_ns value for this clockevent source.
  71          */
  72         sysreg_write(COMPARE, (sysreg_read(COUNT) + delta) ? : 1);
  73
  74         raw_local_irq_restore(flags);
  75
  76         return 0;
  77 }
  78
  79 static void comparator_mode(enum clock_event_mode mode,
  80                 struct clock_event_device *evdev)
  81 {
  82         switch (mode) {
  83         case CLOCK_EVT_MODE_ONESHOT:
  84                 pr_debug("%s: start\n", evdev->name);
  85                 /* FALLTHROUGH */
  86         case CLOCK_EVT_MODE_RESUME:
  87                 cpu_disable_idle_sleep();
  88                 break;
  89         case CLOCK_EVT_MODE_UNUSED:
  90         case CLOCK_EVT_MODE_SHUTDOWN:
  91                 sysreg_write(COMPARE, 0);
  92                 pr_debug("%s: stop\n", evdev->name);
  93                 cpu_enable_idle_sleep();
  94                 break;
  95         default:
  96                 BUG();
  97         }
  98 }
  99
 100 static struct clock_event_device comparator = {
 101         .name           = "avr32_comparator",
 102         .features       = CLOCK_EVT_FEAT_ONESHOT,
 103         .shift          = 16,
 104         .rating         = 50,
 105         .cpumask        = CPU_MASK_CPU0,
 106         .set_next_event = comparator_next_event,
 107         .set_mode       = comparator_mode,
 108 };
 109
 110 void __init time_init(void)
 111 {
 112         unsigned long counter_hz;
 113         int ret;
 114
 115         xtime.tv_sec = mktime(2007, 1, 1, 0, 0, 0);
 116         xtime.tv_nsec = 0;
 117
 118         set_normalized_timespec(&wall_to_monotonic,
 119                                 -xtime.tv_sec, -xtime.tv_nsec);
 120
 121         /* figure rate for counter */
 122         counter_hz = clk_get_rate(boot_cpu_data.clk);
 123         counter.mult = clocksource_hz2mult(counter_hz, counter.shift);
 124
 125         ret = clocksource_register(&counter);
 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
 134         sysreg_write(COMPARE, 0);
 135         timer_irqaction.dev_id = &comparator;
 136
 137         ret = setup_irq(0, &timer_irqaction);
 138         if (ret)
 139                 pr_debug("timer: could not request IRQ 0: %d\n", ret);
 140         else {
 141                 clockevents_register_device(&comparator);
 142
 143                 pr_info("%s: irq 0, %lu.%03lu MHz\n", comparator.name,
 144                                 ((counter_hz + 500) / 1000) / 1000,
 145                                 ((counter_hz + 500) / 1000) % 1000);
 146         }
 147 }