1. 根目录:
2. arch
3. unicore32
4. kernel
5. time.c

/*
 * linux/arch/unicore32/kernel/time.c
 *
 * Code specific to PKUnity SoC and UniCore ISA
 *
 *	Maintained by GUAN Xue-tao <gxt@mprc.pku.edu.cn>
 *	Copyright (C) 2001-2010 Guan Xuetao
 *
 * 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/init.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/timex.h>
#include <linux/clockchips.h>

#include <mach/hardware.h>

#define MIN_OSCR_DELTA 2

static irqreturn_t puv3_ost0_interrupt(int irq, void *dev_id)
{
	struct clock_event_device *c = dev_id;

	/* Disarm the compare/match, signal the event. */
	writel(readl(OST_OIER) & ~OST_OIER_E0, OST_OIER);
	writel(readl(OST_OSSR) & ~OST_OSSR_M0, OST_OSSR);
	c->event_handler(c);

	return IRQ_HANDLED;
}

static int
puv3_osmr0_set_next_event(unsigned long delta, struct clock_event_device *c)
{
	unsigned long next, oscr;

	writel(readl(OST_OIER) | OST_OIER_E0, OST_OIER);
	next = readl(OST_OSCR) + delta;
	writel(next, OST_OSMR0);
	oscr = readl(OST_OSCR);

	return (signed)(next - oscr) <= MIN_OSCR_DELTA ? -ETIME : 0;
}

static void
puv3_osmr0_set_mode(enum clock_event_mode mode, struct clock_event_device *c)
{
	switch (mode) {
	case CLOCK_EVT_MODE_ONESHOT:
	case CLOCK_EVT_MODE_UNUSED:
	case CLOCK_EVT_MODE_SHUTDOWN:
		writel(readl(OST_OIER) & ~OST_OIER_E0, OST_OIER);
		writel(readl(OST_OSSR) & ~OST_OSSR_M0, OST_OSSR);
		break;

	case CLOCK_EVT_MODE_RESUME:
	case CLOCK_EVT_MODE_PERIODIC:
		break;
	}
}

static struct clock_event_device ckevt_puv3_osmr0 = {
	.name		= "osmr0",
	.features	= CLOCK_EVT_FEAT_ONESHOT,
	.rating		= 200,
	.set_next_event	= puv3_osmr0_set_next_event,
	.set_mode	= puv3_osmr0_set_mode,
};

static cycle_t puv3_read_oscr(struct clocksource *cs)
{
	return readl(OST_OSCR);
}

static struct clocksource cksrc_puv3_oscr = {
	.name		= "oscr",
	.rating		= 200,
	.read		= puv3_read_oscr,
	.mask		= CLOCKSOURCE_MASK(32),
	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
};

static struct irqaction puv3_timer_irq = {
	.name		= "ost0",
	.flags		= IRQF_TIMER | IRQF_IRQPOLL,
	.handler	= puv3_ost0_interrupt,
	.dev_id		= &ckevt_puv3_osmr0,
};

void __init time_init(void)
{
	writel(0, OST_OIER);		/* disable any timer interrupts */
	writel(0, OST_OSSR);		/* clear status on all timers */

	clockevents_calc_mult_shift(&ckevt_puv3_osmr0, CLOCK_TICK_RATE, 5);

	ckevt_puv3_osmr0.max_delta_ns =
		clockevent_delta2ns(0x7fffffff, &ckevt_puv3_osmr0);
	ckevt_puv3_osmr0.min_delta_ns =
		clockevent_delta2ns(MIN_OSCR_DELTA * 2, &ckevt_puv3_osmr0) + 1;
	ckevt_puv3_osmr0.cpumask = cpumask_of(0);

	setup_irq(IRQ_TIMER0, &puv3_timer_irq);

	clocksource_register_hz(&cksrc_puv3_oscr, CLOCK_TICK_RATE);
	clockevents_register_device(&ckevt_puv3_osmr0);
}

#ifdef CONFIG_PM
unsigned long osmr[4], oier;

void puv3_timer_suspend(void)
{
	osmr[0] = readl(OST_OSMR0);
	osmr[1] = readl(OST_OSMR1);
	osmr[2] = readl(OST_OSMR2);
	osmr[3] = readl(OST_OSMR3);
	oier = readl(OST_OIER);
}

void puv3_timer_resume(void)
{
	writel(0, OST_OSSR);
	writel(osmr[0], OST_OSMR0);
	writel(osmr[1], OST_OSMR1);
	writel(osmr[2], OST_OSMR2);
	writel(osmr[3], OST_OSMR3);
	writel(oier, OST_OIER);

	/*
	 * OSMR0 is the system timer: make sure OSCR is sufficiently behind
	 */
	writel(readl(OST_OSMR0) - LATCH, OST_OSCR);
}
#else
void puv3_timer_suspend(void) { };
void puv3_timer_resume(void) { };
#endif