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 #include <linux/cpu.h>
  16
  17 #include <asm/sysreg.h>
  18
  19 #include <mach/pm.h>
  20
  21 static bool disable_cpu_idle_poll;
  22
  23 static u64 read_cycle_count(struct clocksource *cs)
  24 {
  25         return (u64)sysreg_read(COUNT);
  26 }
  27
  28 /*
  29  * The architectural cycle count registers are a fine clocksource unless
  30  * the system idle loop use sleep states like "idle":  the CPU cycles
  31  * measured by COUNT (and COMPARE) don't happen during sleep states.
  32  * Their duration also changes if cpufreq changes the CPU clock rate.
  33  * So we rate the clocksource using COUNT as very low quality.
  34  */
  35 static struct clocksource counter = {
  36         .name           = "avr32_counter",
  37         .rating         = 50,
  38         .read           = read_cycle_count,
  39         .mask           = CLOCKSOURCE_MASK(32),
  40         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  41 };
  42
  43 static irqreturn_t timer_interrupt(int irq, void *dev_id)
  44 {
  45         struct clock_event_device *evdev = dev_id;
  46
  47         if (unlikely(!(intc_get_pending(0) & 1)))
  48                 return IRQ_NONE;
  49
  50         /*
  51          * Disable the interrupt until the clockevent subsystem
  52          * reprograms it.
  53          */
  54         sysreg_write(COMPARE, 0);
  55
  56         evdev->event_handler(evdev);
  57         return IRQ_HANDLED;
  58 }
  59
  60 static struct irqaction timer_irqaction = {
  61         .handler        = timer_interrupt,
  62         /* Oprofile uses the same irq as the timer, so allow it to be shared */
  63         .flags          = IRQF_TIMER | IRQF_SHARED,
  64         .name           = "avr32_comparator",
  65 };
  66
  67 static int comparator_next_event(unsigned long delta,
  68                 struct clock_event_device *evdev)
  69 {
  70         unsigned long   flags;
  71
  72         raw_local_irq_save(flags);
  73
  74         /* The time to read COUNT then update COMPARE must be less
  75          * than the min_delta_ns value for this clockevent source.
  76          */
  77         sysreg_write(COMPARE, (sysreg_read(COUNT) + delta) ? : 1);
  78
  79         raw_local_irq_restore(flags);
  80
  81         return 0;
  82 }
  83
  84 static int comparator_shutdown(struct clock_event_device *evdev)
  85 {
  86         pr_debug("%s: %s\n", __func__, evdev->name);
  87         sysreg_write(COMPARE, 0);
  88
  89         if (disable_cpu_idle_poll) {
  90                 disable_cpu_idle_poll = false;
  91                 /*
  92                  * Only disable idle poll if we have forced that
  93                  * in a previous call.
  94                  */
  95                 cpu_idle_poll_ctrl(false);
  96         }
  97         return 0;
  98 }
  99
 100 static int comparator_set_oneshot(struct clock_event_device *evdev)
 101 {
 102         pr_debug("%s: %s\n", __func__, evdev->name);
 103
 104         disable_cpu_idle_poll = true;
 105         /*
 106          * If we're using the COUNT and COMPARE registers we
 107          * need to force idle poll.
 108          */
 109         cpu_idle_poll_ctrl(true);
 110
 111         return 0;
 112 }
 113
 114 static struct clock_event_device comparator = {
 115         .name                   = "avr32_comparator",
 116         .features               = CLOCK_EVT_FEAT_ONESHOT,
 117         .shift                  = 16,
 118         .rating                 = 50,
 119         .set_next_event         = comparator_next_event,
 120         .set_state_shutdown     = comparator_shutdown,
 121         .set_state_oneshot      = comparator_set_oneshot,
 122         .tick_resume            = comparator_set_oneshot,
 123 };
 124
 125 void read_persistent_clock(struct timespec *ts)
 126 {
 127         ts->tv_sec = mktime(2007, 1, 1, 0, 0, 0);
 128         ts->tv_nsec = 0;
 129 }
 130
 131 void __init time_init(void)
 132 {
 133         unsigned long counter_hz;
 134         int ret;
 135
 136         /* figure rate for counter */
 137         counter_hz = clk_get_rate(boot_cpu_data.clk);
 138         ret = clocksource_register_hz(&counter, counter_hz);
 139         if (ret)
 140                 pr_debug("timer: could not register clocksource: %d\n", ret);
 141
 142         /* setup COMPARE clockevent */
 143         comparator.mult = div_sc(counter_hz, NSEC_PER_SEC, comparator.shift);
 144         comparator.max_delta_ns = clockevent_delta2ns((u32)~0, &comparator);
 145         comparator.min_delta_ns = clockevent_delta2ns(50, &comparator) + 1;
 146         comparator.cpumask = cpumask_of(0);
 147
 148         sysreg_write(COMPARE, 0);
 149         timer_irqaction.dev_id = &comparator;
 150
 151         ret = setup_irq(0, &timer_irqaction);
 152         if (ret)
 153                 pr_debug("timer: could not request IRQ 0: %d\n", ret);
 154         else {
 155                 clockevents_register_device(&comparator);
 156
 157                 pr_info("%s: irq 0, %lu.%03lu MHz\n", comparator.name,
 158                                 ((counter_hz + 500) / 1000) / 1000,
 159                                 ((counter_hz + 500) / 1000) % 1000);
 160         }
 161 }