em_sti.c

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/*
 * Emma Mobile Timer Support - STI
 *
 *  Copyright (C) 2012 Magnus Damm
 *
 * 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
 *
 * 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
 */

#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/ioport.h>
#include <linux/io.h>
#include <linux/clk.h>
#include <linux/irq.h>
#include <linux/err.h>
#include <linux/delay.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/slab.h>
#include <linux/module.h>

enum { USER_CLOCKSOURCE, USER_CLOCKEVENT, USER_NR };

struct em_sti_priv {
    void __iomem *base;
    struct clk *clk;
    struct platform_device *pdev;
    unsigned int active[USER_NR];
    unsigned long rate;
    raw_spinlock_t lock;
    struct clock_event_device ced;
    struct clocksource cs;
};

#define STI_CONTROL 0x00
#define STI_COMPA_H 0x10
#define STI_COMPA_L 0x14
#define STI_COMPB_H 0x18
#define STI_COMPB_L 0x1c
#define STI_COUNT_H 0x20
#define STI_COUNT_L 0x24
#define STI_COUNT_RAW_H 0x28
#define STI_COUNT_RAW_L 0x2c
#define STI_SET_H 0x30
#define STI_SET_L 0x34
#define STI_INTSTATUS 0x40
#define STI_INTRAWSTATUS 0x44
#define STI_INTENSET 0x48
#define STI_INTENCLR 0x4c
#define STI_INTFFCLR 0x50

static inline unsigned long em_sti_read(struct em_sti_priv *p, int offs)
{
    return ioread32(p->base + offs);
}

static inline void em_sti_write(struct em_sti_priv *p, int offs,
                unsigned long value)
{
    iowrite32(value, p->base + offs);
}

static int em_sti_enable(struct em_sti_priv *p)
{
    int ret;

    /* enable clock */
    ret = clk_enable(p->clk);
    if (ret) {
        dev_err(&p->pdev->dev, "cannot enable clock\n");
        return ret;
    }

    /* configure channel, periodic mode and maximum timeout */
    p->rate = clk_get_rate(p->clk);

    /* reset the counter */
    em_sti_write(p, STI_SET_H, 0x40000000);
    em_sti_write(p, STI_SET_L, 0x00000000);

    /* mask and clear pending interrupts */
    em_sti_write(p, STI_INTENCLR, 3);
    em_sti_write(p, STI_INTFFCLR, 3);

    /* enable updates of counter registers */
    em_sti_write(p, STI_CONTROL, 1);

    return 0;
}

static void em_sti_disable(struct em_sti_priv *p)
{
    /* mask interrupts */
    em_sti_write(p, STI_INTENCLR, 3);

    /* stop clock */
    clk_disable(p->clk);
}

static cycle_t em_sti_count(struct em_sti_priv *p)
{
    cycle_t ticks;
    unsigned long flags;

    /* the STI hardware buffers the 48-bit count, but to
     * break it out into two 32-bit access the registers
     * must be accessed in a certain order.
     * Always read STI_COUNT_H before STI_COUNT_L.
     */
    raw_spin_lock_irqsave(&p->lock, flags);
    ticks = (cycle_t)(em_sti_read(p, STI_COUNT_H) & 0xffff) << 32;
    ticks |= em_sti_read(p, STI_COUNT_L);
    raw_spin_unlock_irqrestore(&p->lock, flags);

    return ticks;
}

static cycle_t em_sti_set_next(struct em_sti_priv *p, cycle_t next)
{
    unsigned long flags;

    raw_spin_lock_irqsave(&p->lock, flags);

    /* mask compare A interrupt */
    em_sti_write(p, STI_INTENCLR, 1);

    /* update compare A value */
    em_sti_write(p, STI_COMPA_H, next >> 32);
    em_sti_write(p, STI_COMPA_L, next & 0xffffffff);

    /* clear compare A interrupt source */
    em_sti_write(p, STI_INTFFCLR, 1);

    /* unmask compare A interrupt */
    em_sti_write(p, STI_INTENSET, 1);

    raw_spin_unlock_irqrestore(&p->lock, flags);

    return next;
}

static irqreturn_t em_sti_interrupt(int irq, void *dev_id)
{
    struct em_sti_priv *p = dev_id;

    p->ced.event_handler(&p->ced);
    return IRQ_HANDLED;
}

static int em_sti_start(struct em_sti_priv *p, unsigned int user)
{
    unsigned long flags;
    int used_before;
    int ret = 0;

    raw_spin_lock_irqsave(&p->lock, flags);
    used_before = p->active[USER_CLOCKSOURCE] | p->active[USER_CLOCKEVENT];
    if (!used_before)
        ret = em_sti_enable(p);

    if (!ret)
        p->active[user] = 1;
    raw_spin_unlock_irqrestore(&p->lock, flags);

    return ret;
}

static void em_sti_stop(struct em_sti_priv *p, unsigned int user)
{
    unsigned long flags;
    int used_before, used_after;

    raw_spin_lock_irqsave(&p->lock, flags);
    used_before = p->active[USER_CLOCKSOURCE] | p->active[USER_CLOCKEVENT];
    p->active[user] = 0;
    used_after = p->active[USER_CLOCKSOURCE] | p->active[USER_CLOCKEVENT];

    if (used_before && !used_after)
        em_sti_disable(p);
    raw_spin_unlock_irqrestore(&p->lock, flags);
}

static struct em_sti_priv *cs_to_em_sti(struct clocksource *cs)
{
    return container_of(cs, struct em_sti_priv, cs);
}

static cycle_t em_sti_clocksource_read(struct clocksource *cs)
{
    return em_sti_count(cs_to_em_sti(cs));
}

static int em_sti_clocksource_enable(struct clocksource *cs)
{
    int ret;
    struct em_sti_priv *p = cs_to_em_sti(cs);

    ret = em_sti_start(p, USER_CLOCKSOURCE);
    if (!ret)
        __clocksource_updatefreq_hz(cs, p->rate);
    return ret;
}

static void em_sti_clocksource_disable(struct clocksource *cs)
{
    em_sti_stop(cs_to_em_sti(cs), USER_CLOCKSOURCE);
}

static void em_sti_clocksource_resume(struct clocksource *cs)
{
    em_sti_clocksource_enable(cs);
}

static int em_sti_register_clocksource(struct em_sti_priv *p)
{
    struct clocksource *cs = &p->cs;

    memset(cs, 0, sizeof(*cs));
    cs->name = dev_name(&p->pdev->dev);
    cs->rating = 200;
    cs->read = em_sti_clocksource_read;
    cs->enable = em_sti_clocksource_enable;
    cs->disable = em_sti_clocksource_disable;
    cs->suspend = em_sti_clocksource_disable;
    cs->resume = em_sti_clocksource_resume;
    cs->mask = CLOCKSOURCE_MASK(48);
    cs->flags = CLOCK_SOURCE_IS_CONTINUOUS;

    dev_info(&p->pdev->dev, "used as clock source\n");

    /* Register with dummy 1 Hz value, gets updated in ->enable() */
    clocksource_register_hz(cs, 1);
    return 0;
}

static struct em_sti_priv *ced_to_em_sti(struct clock_event_device *ced)
{
    return container_of(ced, struct em_sti_priv, ced);
}

static void em_sti_clock_event_mode(enum clock_event_mode mode,
                    struct clock_event_device *ced)
{
    struct em_sti_priv *p = ced_to_em_sti(ced);

    /* deal with old setting first */
    switch (ced->mode) {
    case CLOCK_EVT_MODE_ONESHOT:
        em_sti_stop(p, USER_CLOCKEVENT);
        break;
    default:
        break;
    }

    switch (mode) {
    case CLOCK_EVT_MODE_ONESHOT:
        dev_info(&p->pdev->dev, "used for oneshot clock events\n");
        em_sti_start(p, USER_CLOCKEVENT);
        clockevents_config(&p->ced, p->rate);
        break;
    case CLOCK_EVT_MODE_SHUTDOWN:
    case CLOCK_EVT_MODE_UNUSED:
        em_sti_stop(p, USER_CLOCKEVENT);
        break;
    default:
        break;
    }
}

static int em_sti_clock_event_next(unsigned long delta,
                   struct clock_event_device *ced)
{
    struct em_sti_priv *p = ced_to_em_sti(ced);
    cycle_t next;
    int safe;

    next = em_sti_set_next(p, em_sti_count(p) + delta);
    safe = em_sti_count(p) < (next - 1);

    return !safe;
}

static void em_sti_register_clockevent(struct em_sti_priv *p)
{
    struct clock_event_device *ced = &p->ced;

    memset(ced, 0, sizeof(*ced));
    ced->name = dev_name(&p->pdev->dev);
    ced->features = CLOCK_EVT_FEAT_ONESHOT;
    ced->rating = 200;
    ced->cpumask = cpumask_of(0);
    ced->set_next_event = em_sti_clock_event_next;
    ced->set_mode = em_sti_clock_event_mode;

    dev_info(&p->pdev->dev, "used for clock events\n");

    /* Register with dummy 1 Hz value, gets updated in ->set_mode() */
    clockevents_config_and_register(ced, 1, 2, 0xffffffff);
}

static int __devinit em_sti_probe(struct platform_device *pdev)
{
    struct em_sti_priv *p;
    struct resource *res;
    int irq, ret;

    p = kzalloc(sizeof(*p), GFP_KERNEL);
    if (p == NULL) {
        dev_err(&pdev->dev, "failed to allocate driver data\n");
        ret = -ENOMEM;
        goto err0;
    }

    p->pdev = pdev;
    platform_set_drvdata(pdev, p);

    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    if (!res) {
        dev_err(&pdev->dev, "failed to get I/O memory\n");
        ret = -EINVAL;
        goto err0;
    }

    irq = platform_get_irq(pdev, 0);
    if (irq < 0) {
        dev_err(&pdev->dev, "failed to get irq\n");
        ret = -EINVAL;
        goto err0;
    }

    /* map memory, let base point to the STI instance */
    p->base = ioremap_nocache(res->start, resource_size(res));
    if (p->base == NULL) {
        dev_err(&pdev->dev, "failed to remap I/O memory\n");
        ret = -ENXIO;
        goto err0;
    }

    /* get hold of clock */
    p->clk = clk_get(&pdev->dev, "sclk");
    if (IS_ERR(p->clk)) {
        dev_err(&pdev->dev, "cannot get clock\n");
        ret = PTR_ERR(p->clk);
        goto err1;
    }

    if (request_irq(irq, em_sti_interrupt,
            IRQF_TIMER | IRQF_IRQPOLL | IRQF_NOBALANCING,
            dev_name(&pdev->dev), p)) {
        dev_err(&pdev->dev, "failed to request low IRQ\n");
        ret = -ENOENT;
        goto err2;
    }

    raw_spin_lock_init(&p->lock);
    em_sti_register_clockevent(p);
    em_sti_register_clocksource(p);
    return 0;

err2:
    clk_put(p->clk);
err1:
    iounmap(p->base);
err0:
    kfree(p);
    return ret;
}

static int __devexit em_sti_remove(struct platform_device *pdev)
{
    return -EBUSY; /* cannot unregister clockevent and clocksource */
}

static const struct of_device_id em_sti_dt_ids[] __devinitconst = {
    { .compatible = "renesas,em-sti", },
    {},
};
MODULE_DEVICE_TABLE(of, em_sti_dt_ids);

static struct platform_driver em_sti_device_driver = {
    .probe      = em_sti_probe,
    .remove     = __devexit_p(em_sti_remove),
    .driver     = {
        .name   = "em_sti",
        .of_match_table = em_sti_dt_ids,
    }
};

module_platform_driver(em_sti_device_driver);

MODULE_AUTHOR("Magnus Damm");
MODULE_DESCRIPTION("Renesas Emma Mobile STI Timer Driver");
MODULE_LICENSE("GPL v2");