timer.c

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/*
 *  arch/arm/mach-vt8500/timer_dt.c
 *
 *  Copyright (C) 2012 Tony Prisk <[email protected]>
 *  Copyright (C) 2010 Alexey Charkov <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/*
 * This file is copied and modified from the original timer.c provided by
 * Alexey Charkov. Minor changes have been made for Device Tree Support.
 */

#include <linux/io.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/delay.h>
#include <asm/mach/time.h>

#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>

#define VT8500_TIMER_OFFSET 0x0100
#define VT8500_TIMER_HZ     3000000
#define TIMER_MATCH_VAL     0x0000
#define TIMER_COUNT_VAL     0x0010
#define TIMER_STATUS_VAL    0x0014
#define TIMER_IER_VAL       0x001c      /* interrupt enable */
#define TIMER_CTRL_VAL      0x0020
#define TIMER_AS_VAL        0x0024      /* access status */
#define TIMER_COUNT_R_ACTIVE    (1 << 5)    /* not ready for read */
#define TIMER_COUNT_W_ACTIVE    (1 << 4)    /* not ready for write */
#define TIMER_MATCH_W_ACTIVE    (1 << 0)    /* not ready for write */

#define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)

static void __iomem *regbase;

static cycle_t vt8500_timer_read(struct clocksource *cs)
{
    int loops = msecs_to_loops(10);
    writel(3, regbase + TIMER_CTRL_VAL);
    while ((readl((regbase + TIMER_AS_VAL)) & TIMER_COUNT_R_ACTIVE)
                        && --loops)
        cpu_relax();
    return readl(regbase + TIMER_COUNT_VAL);
}

static struct clocksource clocksource = {
    .name           = "vt8500_timer",
    .rating         = 200,
    .read           = vt8500_timer_read,
    .mask           = CLOCKSOURCE_MASK(32),
    .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
};

static int vt8500_timer_set_next_event(unsigned long cycles,
                    struct clock_event_device *evt)
{
    int loops = msecs_to_loops(10);
    cycle_t alarm = clocksource.read(&clocksource) + cycles;
    while ((readl(regbase + TIMER_AS_VAL) & TIMER_MATCH_W_ACTIVE)
                        && --loops)
        cpu_relax();
    writel((unsigned long)alarm, regbase + TIMER_MATCH_VAL);

    if ((signed)(alarm - clocksource.read(&clocksource)) <= 16)
        return -ETIME;

    writel(1, regbase + TIMER_IER_VAL);

    return 0;
}

static void vt8500_timer_set_mode(enum clock_event_mode mode,
                  struct clock_event_device *evt)
{
    switch (mode) {
    case CLOCK_EVT_MODE_RESUME:
    case CLOCK_EVT_MODE_PERIODIC:
        break;
    case CLOCK_EVT_MODE_ONESHOT:
    case CLOCK_EVT_MODE_UNUSED:
    case CLOCK_EVT_MODE_SHUTDOWN:
        writel(readl(regbase + TIMER_CTRL_VAL) | 1,
            regbase + TIMER_CTRL_VAL);
        writel(0, regbase + TIMER_IER_VAL);
        break;
    }
}

static struct clock_event_device clockevent = {
    .name           = "vt8500_timer",
    .features       = CLOCK_EVT_FEAT_ONESHOT,
    .rating         = 200,
    .set_next_event = vt8500_timer_set_next_event,
    .set_mode       = vt8500_timer_set_mode,
};

static irqreturn_t vt8500_timer_interrupt(int irq, void *dev_id)
{
    struct clock_event_device *evt = dev_id;
    writel(0xf, regbase + TIMER_STATUS_VAL);
    evt->event_handler(evt);

    return IRQ_HANDLED;
}

static struct irqaction irq = {
    .name    = "vt8500_timer",
    .flags   = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
    .handler = vt8500_timer_interrupt,
    .dev_id  = &clockevent,
};

static struct of_device_id vt8500_timer_ids[] = {
    { .compatible = "via,vt8500-timer" },
    { }
};

void __init vt8500_timer_init(void)
{
    struct device_node *np;
    int timer_irq;

    np = of_find_matching_node(NULL, vt8500_timer_ids);
    if (!np) {
        pr_err("%s: Timer description missing from Device Tree\n",
                                __func__);
        return;
    }
    regbase = of_iomap(np, 0);
    if (!regbase) {
        pr_err("%s: Missing iobase description in Device Tree\n",
                                __func__);
        of_node_put(np);
        return;
    }
    timer_irq = irq_of_parse_and_map(np, 0);
    if (!timer_irq) {
        pr_err("%s: Missing irq description in Device Tree\n",
                                __func__);
        of_node_put(np);
        return;
    }

    writel(1, regbase + TIMER_CTRL_VAL);
    writel(0xf, regbase + TIMER_STATUS_VAL);
    writel(~0, regbase + TIMER_MATCH_VAL);

    if (clocksource_register_hz(&clocksource, VT8500_TIMER_HZ))
        pr_err("%s: vt8500_timer_init: clocksource_register failed for %s\n",
                    __func__, clocksource.name);

    clockevents_calc_mult_shift(&clockevent, VT8500_TIMER_HZ, 4);

    /* copy-pasted from mach-msm; no idea */
    clockevent.max_delta_ns =
        clockevent_delta2ns(0xf0000000, &clockevent);
    clockevent.min_delta_ns = clockevent_delta2ns(4, &clockevent);
    clockevent.cpumask = cpumask_of(0);

    if (setup_irq(timer_irq, &irq))
        pr_err("%s: setup_irq failed for %s\n", __func__,
                            clockevent.name);
    clockevents_register_device(&clockevent);
}