/*
 * arch/arm/mach-pxa/time.c
 *
 * PXA clocksource, clockevents, and OST interrupt handlers.
 * Copyright (c) 2007 by Bill Gatliff <bgat@billgatliff.com>.
 *
 * Derived from Nicolas Pitre's PXA timer handler Copyright (c) 2001
 * by MontaVista Software, Inc.  (Nico, your code rocks!)
 *
 * 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/kernel.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/clk.h>
#include <linux/clockchips.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/sched_clock.h>

#include <asm/div64.h>

#define OSMR0           0x00    /* OS Timer 0 Match Register */
#define OSMR1           0x04    /* OS Timer 1 Match Register */
#define OSMR2           0x08    /* OS Timer 2 Match Register */
#define OSMR3           0x0C    /* OS Timer 3 Match Register */

#define OSCR            0x10    /* OS Timer Counter Register */
#define OSSR            0x14    /* OS Timer Status Register */
#define OWER            0x18    /* OS Timer Watchdog Enable Register */
#define OIER            0x1C    /* OS Timer Interrupt Enable Register */

#define OSSR_M3         (1 << 3)        /* Match status channel 3 */
#define OSSR_M2         (1 << 2)        /* Match status channel 2 */
#define OSSR_M1         (1 << 1)        /* Match status channel 1 */
#define OSSR_M0         (1 << 0)        /* Match status channel 0 */

#define OIER_E0         (1 << 0)        /* Interrupt enable channel 0 */

/*
 * This is PXA's sched_clock implementation. This has a resolution
 * of at least 308 ns and a maximum value of 208 days.
 *
 * The return value is guaranteed to be monotonic in that range as
 * long as there is always less than 582 seconds between successive
 * calls to sched_clock() which should always be the case in practice.
 */

#define timer_readl(reg) readl_relaxed(timer_base + (reg))
#define timer_writel(val, reg) writel_relaxed((val), timer_base + (reg))

static void __iomem *timer_base;

static u64 notrace pxa_read_sched_clock(void)
{
        return timer_readl(OSCR);
}


#define MIN_OSCR_DELTA 16

static irqreturn_t
pxa_ost0_interrupt(int irq, void *dev_id)
{
        struct clock_event_device *c = dev_id;

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

        return IRQ_HANDLED;
}

static int
pxa_osmr0_set_next_event(unsigned long delta, struct clock_event_device *dev)
{
        unsigned long next, oscr;

        timer_writel(timer_readl(OIER) | OIER_E0, OIER);
        next = timer_readl(OSCR) + delta;
        timer_writel(next, OSMR0);
        oscr = timer_readl(OSCR);

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

static void
pxa_osmr0_set_mode(enum clock_event_mode mode, struct clock_event_device *dev)
{
        switch (mode) {
        case CLOCK_EVT_MODE_ONESHOT:
                timer_writel(timer_readl(OIER) & ~OIER_E0, OIER);
                timer_writel(OSSR_M0, OSSR);
                break;

        case CLOCK_EVT_MODE_UNUSED:
        case CLOCK_EVT_MODE_SHUTDOWN:
                /* initializing, released, or preparing for suspend */
                timer_writel(timer_readl(OIER) & ~OIER_E0, OIER);
                timer_writel(OSSR_M0, OSSR);
                break;

        case CLOCK_EVT_MODE_RESUME:
        case CLOCK_EVT_MODE_PERIODIC:
                break;
        }
}

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

static void pxa_timer_suspend(struct clock_event_device *cedev)
{
        osmr[0] = timer_readl(OSMR0);
        osmr[1] = timer_readl(OSMR1);
        osmr[2] = timer_readl(OSMR2);
        osmr[3] = timer_readl(OSMR3);
        oier = timer_readl(OIER);
        oscr = timer_readl(OSCR);
}

static void pxa_timer_resume(struct clock_event_device *cedev)
{
        /*
         * Ensure that we have at least MIN_OSCR_DELTA between match
         * register 0 and the OSCR, to guarantee that we will receive
         * the one-shot timer interrupt.  We adjust OSMR0 in preference
         * to OSCR to guarantee that OSCR is monotonically incrementing.
         */
        if (osmr[0] - oscr < MIN_OSCR_DELTA)
                osmr[0] += MIN_OSCR_DELTA;

        timer_writel(osmr[0], OSMR0);
        timer_writel(osmr[1], OSMR1);
        timer_writel(osmr[2], OSMR2);
        timer_writel(osmr[3], OSMR3);
        timer_writel(oier, OIER);
        timer_writel(oscr, OSCR);
}
#else
#define pxa_timer_suspend NULL
#define pxa_timer_resume NULL
#endif

static struct clock_event_device ckevt_pxa_osmr0 = {
        .name           = "osmr0",
        .features       = CLOCK_EVT_FEAT_ONESHOT,
        .rating         = 200,
        .set_next_event = pxa_osmr0_set_next_event,
        .set_mode       = pxa_osmr0_set_mode,
        .suspend        = pxa_timer_suspend,
        .resume         = pxa_timer_resume,
};

static struct irqaction pxa_ost0_irq = {
        .name           = "ost0",
        .flags          = IRQF_TIMER | IRQF_IRQPOLL,
        .handler        = pxa_ost0_interrupt,
        .dev_id         = &ckevt_pxa_osmr0,
};

static void pxa_timer_common_init(int irq, unsigned long clock_tick_rate)
{
        timer_writel(0, OIER);
        timer_writel(OSSR_M0 | OSSR_M1 | OSSR_M2 | OSSR_M3, OSSR);

        sched_clock_register(pxa_read_sched_clock, 32, clock_tick_rate);

        ckevt_pxa_osmr0.cpumask = cpumask_of(0);

        setup_irq(irq, &pxa_ost0_irq);

        clocksource_mmio_init(timer_base + OSCR, "oscr0", clock_tick_rate, 200,
                              32, clocksource_mmio_readl_up);
        clockevents_config_and_register(&ckevt_pxa_osmr0, clock_tick_rate,
                                        MIN_OSCR_DELTA * 2, 0x7fffffff);
}

static void __init pxa_timer_dt_init(struct device_node *np)
{
        struct clk *clk;
        int irq;

        /* timer registers are shared with watchdog timer */
        timer_base = of_iomap(np, 0);
        if (!timer_base)
                panic("%s: unable to map resource\n", np->name);

        clk = of_clk_get(np, 0);
        if (IS_ERR(clk)) {
                pr_crit("%s: unable to get clk\n", np->name);
                return;
        }
        clk_prepare_enable(clk);

        /* we are only interested in OS-timer0 irq */
        irq = irq_of_parse_and_map(np, 0);
        if (irq <= 0) {
                pr_crit("%s: unable to parse OS-timer0 irq\n", np->name);
                return;
        }

        pxa_timer_common_init(irq, clk_get_rate(clk));
}
CLOCKSOURCE_OF_DECLARE(pxa_timer, "marvell,pxa-timer", pxa_timer_dt_init);

/*
 * Legacy timer init for non device-tree boards.
 */
void __init pxa_timer_nodt_init(int irq, void __iomem *base,
        unsigned long clock_tick_rate)
{
        struct clk *clk;

        timer_base = base;
        clk = clk_get(NULL, "OSTIMER0");
        if (clk && !IS_ERR(clk))
                clk_prepare_enable(clk);
        else
                pr_crit("%s: unable to get clk\n", __func__);

        pxa_timer_common_init(irq, clock_tick_rate);
}