/*
 * linux/arch/arm/mach-sa1100/time.c
 *
 * Copyright (C) 1998 Deborah Wallach.
 * Twiddles  (C) 1999 Hugo Fiennes <hugo@empeg.com>
 *
 * 2000/03/29 (C) Nicolas Pitre <nico@fluxnic.net>
 *	Rewritten: big cleanup, much simpler, better HZ accuracy.
 *
 */
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/sched.h>	/* just for sched_clock() - funny that */
#include <linux/timex.h>
#include <linux/clockchips.h>

#include <asm/mach/time.h>
#include <asm/sched_clock.h>
#include <mach/hardware.h>

/*
 * This is the SA11x0 sched_clock implementation.
 */
static DEFINE_CLOCK_DATA(cd);

/*
 * Constants generated by clocks_calc_mult_shift(m, s, 3.6864MHz,
 * NSEC_PER_SEC, 60).
 * This gives a resolution of about 271ns and a wrap period of about 19min.
 */
#define SC_MULT		2275555556u
#define SC_SHIFT	23

unsigned long long notrace sched_clock(void)
{
	u32 cyc = OSCR;
	return cyc_to_fixed_sched_clock(&cd, cyc, (u32)~0, SC_MULT, SC_SHIFT);
}

static void notrace sa1100_update_sched_clock(void)
{
	u32 cyc = OSCR;
	update_sched_clock(&cd, cyc, (u32)~0);
}

#define MIN_OSCR_DELTA 2

static irqreturn_t sa1100_ost0_interrupt(int irq, void *dev_id)
{
	struct clock_event_device *c = dev_id;

	/* Disarm the compare/match, signal the event. */
	OIER &= ~OIER_E0;
	OSSR = OSSR_M0;
	c->event_handler(c);

	return IRQ_HANDLED;
}

static int
sa1100_osmr0_set_next_event(unsigned long delta, struct clock_event_device *c)
{
	unsigned long next, oscr;

	OIER |= OIER_E0;
	next = OSCR + delta;
	OSMR0 = next;
	oscr = OSCR;

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

static void
sa1100_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:
		OIER &= ~OIER_E0;
		OSSR = OSSR_M0;
		break;

	case CLOCK_EVT_MODE_RESUME:
	case CLOCK_EVT_MODE_PERIODIC:
		break;
	}
}

static struct clock_event_device ckevt_sa1100_osmr0 = {
	.name		= "osmr0",
	.features	= CLOCK_EVT_FEAT_ONESHOT,
	.rating		= 200,
	.set_next_event	= sa1100_osmr0_set_next_event,
	.set_mode	= sa1100_osmr0_set_mode,
};

static cycle_t sa1100_read_oscr(struct clocksource *s)
{
	return OSCR;
}

static struct clocksource cksrc_sa1100_oscr = {
	.name		= "oscr",
	.rating		= 200,
	.read		= sa1100_read_oscr,
	.mask		= CLOCKSOURCE_MASK(32),
	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
};

static struct irqaction sa1100_timer_irq = {
	.name		= "ost0",
	.flags		= IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
	.handler	= sa1100_ost0_interrupt,
	.dev_id		= &ckevt_sa1100_osmr0,
};

static void __init sa1100_timer_init(void)
{
	OIER = 0;
	OSSR = OSSR_M0 | OSSR_M1 | OSSR_M2 | OSSR_M3;

	init_fixed_sched_clock(&cd, sa1100_update_sched_clock, 32,
			       3686400, SC_MULT, SC_SHIFT);

	clockevents_calc_mult_shift(&ckevt_sa1100_osmr0, 3686400, 4);
	ckevt_sa1100_osmr0.max_delta_ns =
		clockevent_delta2ns(0x7fffffff, &ckevt_sa1100_osmr0);
	ckevt_sa1100_osmr0.min_delta_ns =
		clockevent_delta2ns(MIN_OSCR_DELTA * 2, &ckevt_sa1100_osmr0) + 1;
	ckevt_sa1100_osmr0.cpumask = cpumask_of(0);

	setup_irq(IRQ_OST0, &sa1100_timer_irq);

	clocksource_register_hz(&cksrc_sa1100_oscr, CLOCK_TICK_RATE);
	clockevents_register_device(&ckevt_sa1100_osmr0);
}

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

static void sa1100_timer_suspend(void)
{
	osmr[0] = OSMR0;
	osmr[1] = OSMR1;
	osmr[2] = OSMR2;
	osmr[3] = OSMR3;
	oier = OIER;
}

static void sa1100_timer_resume(void)
{
	OSSR = 0x0f;
	OSMR0 = osmr[0];
	OSMR1 = osmr[1];
	OSMR2 = osmr[2];
	OSMR3 = osmr[3];
	OIER = oier;

	/*
	 * OSMR0 is the system timer: make sure OSCR is sufficiently behind
	 */
	OSCR = OSMR0 - LATCH;
}
#else
#define sa1100_timer_suspend NULL
#define sa1100_timer_resume NULL
#endif

struct sys_timer sa1100_timer = {
	.init		= sa1100_timer_init,
	.suspend	= sa1100_timer_suspend,
	.resume		= sa1100_timer_resume,
};