linux/arch/avr32/kernel/time.c

/*
 * Copyright (C) 2004-2007 Atmel Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/clk.h>
#include <linux/clockchips.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/kernel.h>
#include <linux/time.h>

#include <asm/sysreg.h>

#include <asm/arch/pm.h>


static cycle_t read_cycle_count(void)
{
	return (cycle_t)sysreg_read(COUNT);
}

/*
 * The architectural cycle count registers are a fine clocksource unless
 * the system idle loop use sleep states like "idle":  the CPU cycles
 * measured by COUNT (and COMPARE) don't happen during sleep states.
 * Their duration also changes if cpufreq changes the CPU clock rate.
 * So we rate the clocksource using COUNT as very low quality.
 */
static struct clocksource counter = {
	.name		= "avr32_counter",
	.rating		= 50,
	.read		= read_cycle_count,
	.mask		= CLOCKSOURCE_MASK(32),
	.shift		= 16,
	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
};

static irqreturn_t timer_interrupt(int irq, void *dev_id)
{
	struct clock_event_device *evdev = dev_id;

	/*
	 * Disable the interrupt until the clockevent subsystem
	 * reprograms it.
	 */
	sysreg_write(COMPARE, 0);

	evdev->event_handler(evdev);
	return IRQ_HANDLED;
}

static struct irqaction timer_irqaction = {
	.handler	= timer_interrupt,
	.flags		= IRQF_TIMER | IRQF_DISABLED,
	.name		= "avr32_comparator",
};

static int comparator_next_event(unsigned long delta,
		struct clock_event_device *evdev)
{
	unsigned long	flags;

	raw_local_irq_save(flags);

	/* The time to read COUNT then update COMPARE must be less
	 * than the min_delta_ns value for this clockevent source.
	 */
	sysreg_write(COMPARE, (sysreg_read(COUNT) + delta) ? : 1);

	raw_local_irq_restore(flags);

	return 0;
}

static void comparator_mode(enum clock_event_mode mode,
		struct clock_event_device *evdev)
{
	switch (mode) {
	case CLOCK_EVT_MODE_ONESHOT:
		pr_debug("%s: start\n", evdev->name);
		/* FALLTHROUGH */
	case CLOCK_EVT_MODE_RESUME:
		cpu_disable_idle_sleep();
		break;
	case CLOCK_EVT_MODE_UNUSED:
	case CLOCK_EVT_MODE_SHUTDOWN:
		sysreg_write(COMPARE, 0);
		pr_debug("%s: stop\n", evdev->name);
		cpu_enable_idle_sleep();
		break;
	default:
		BUG();
	}
}

static struct clock_event_device comparator = {
	.name		= "avr32_comparator",
	.features	= CLOCK_EVT_FEAT_ONESHOT,
	.shift		= 16,
	.rating		= 50,
	.cpumask	= CPU_MASK_CPU0,
	.set_next_event	= comparator_next_event,
	.set_mode	= comparator_mode,
};

void __init time_init(void)
{
	unsigned long counter_hz;
	int ret;

	xtime.tv_sec = mktime(2007, 1, 1, 0, 0, 0);
	xtime.tv_nsec = 0;

	set_normalized_timespec(&wall_to_monotonic,
				-xtime.tv_sec, -xtime.tv_nsec);

	/* figure rate for counter */
	counter_hz = clk_get_rate(boot_cpu_data.clk);
	counter.mult = clocksource_hz2mult(counter_hz, counter.shift);

	ret = clocksource_register(&counter);
	if (ret)
		pr_debug("timer: could not register clocksource: %d\n", ret);

	/* setup COMPARE clockevent */
	comparator.mult = div_sc(counter_hz, NSEC_PER_SEC, comparator.shift);
	comparator.max_delta_ns = clockevent_delta2ns((u32)~0, &comparator);
	comparator.min_delta_ns = clockevent_delta2ns(50, &comparator) + 1;

	sysreg_write(COMPARE, 0);
	timer_irqaction.dev_id = &comparator;

	ret = setup_irq(0, &timer_irqaction);
	if (ret)
		pr_debug("timer: could not request IRQ 0: %d\n", ret);
	else {
		clockevents_register_device(&comparator);

		pr_info("%s: irq 0, %lu.%03lu MHz\n", comparator.name,
				((counter_hz + 500) / 1000) / 1000,
				((counter_hz + 500) / 1000) % 1000);
	}
}