ptp_clock.c

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/*
 * PTP 1588 clock support
 *
 * Copyright (C) 2010 OMICRON electronics GmbH
 *
 *  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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
#include <linux/bitops.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/posix-clock.h>
#include <linux/pps_kernel.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#include <linux/uaccess.h>

#include "ptp_private.h"

#define PTP_MAX_ALARMS 4
#define PTP_MAX_CLOCKS 8
#define PTP_PPS_DEFAULTS (PPS_CAPTUREASSERT | PPS_OFFSETASSERT)
#define PTP_PPS_EVENT PPS_CAPTUREASSERT
#define PTP_PPS_MODE (PTP_PPS_DEFAULTS | PPS_CANWAIT | PPS_TSFMT_TSPEC)

/* private globals */

static dev_t ptp_devt;
static struct class *ptp_class;

static DECLARE_BITMAP(ptp_clocks_map, PTP_MAX_CLOCKS);
static DEFINE_MUTEX(ptp_clocks_mutex); /* protects 'ptp_clocks_map' */

/* time stamp event queue operations */

static inline int queue_free(struct timestamp_event_queue *q)
{
    return PTP_MAX_TIMESTAMPS - queue_cnt(q) - 1;
}

static void enqueue_external_timestamp(struct timestamp_event_queue *queue,
                       struct ptp_clock_event *src)
{
    struct ptp_extts_event *dst;
    unsigned long flags;
    s64 seconds;
    u32 remainder;

    seconds = div_u64_rem(src->timestamp, 1000000000, &remainder);

    spin_lock_irqsave(&queue->lock, flags);

    dst = &queue->buf[queue->tail];
    dst->index = src->index;
    dst->t.sec = seconds;
    dst->t.nsec = remainder;

    if (!queue_free(queue))
        queue->head = (queue->head + 1) % PTP_MAX_TIMESTAMPS;

    queue->tail = (queue->tail + 1) % PTP_MAX_TIMESTAMPS;

    spin_unlock_irqrestore(&queue->lock, flags);
}

static s32 scaled_ppm_to_ppb(long ppm)
{
    /*
     * The 'freq' field in the 'struct timex' is in parts per
     * million, but with a 16 bit binary fractional field.
     *
     * We want to calculate
     *
     *    ppb = scaled_ppm * 1000 / 2^16
     *
     * which simplifies to
     *
     *    ppb = scaled_ppm * 125 / 2^13
     */
    s64 ppb = 1 + ppm;
    ppb *= 125;
    ppb >>= 13;
    return (s32) ppb;
}

/* posix clock implementation */

static int ptp_clock_getres(struct posix_clock *pc, struct timespec *tp)
{
    tp->tv_sec = 0;
    tp->tv_nsec = 1;
    return 0;
}

static int ptp_clock_settime(struct posix_clock *pc, const struct timespec *tp)
{
    struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
    return ptp->info->settime(ptp->info, tp);
}

static int ptp_clock_gettime(struct posix_clock *pc, struct timespec *tp)
{
    struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
    return ptp->info->gettime(ptp->info, tp);
}

static int ptp_clock_adjtime(struct posix_clock *pc, struct timex *tx)
{
    struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
    struct ptp_clock_info *ops;
    int err = -EOPNOTSUPP;

    ops = ptp->info;

    if (tx->modes & ADJ_SETOFFSET) {
        struct timespec ts;
        ktime_t kt;
        s64 delta;

        ts.tv_sec  = tx->time.tv_sec;
        ts.tv_nsec = tx->time.tv_usec;

        if (!(tx->modes & ADJ_NANO))
            ts.tv_nsec *= 1000;

        if ((unsigned long) ts.tv_nsec >= NSEC_PER_SEC)
            return -EINVAL;

        kt = timespec_to_ktime(ts);
        delta = ktime_to_ns(kt);
        err = ops->adjtime(ops, delta);
    } else if (tx->modes & ADJ_FREQUENCY) {
        err = ops->adjfreq(ops, scaled_ppm_to_ppb(tx->freq));
        ptp->dialed_frequency = tx->freq;
    } else if (tx->modes == 0) {
        tx->freq = ptp->dialed_frequency;
        err = 0;
    }

    return err;
}

static struct posix_clock_operations ptp_clock_ops = {
    .owner      = THIS_MODULE,
    .clock_adjtime  = ptp_clock_adjtime,
    .clock_gettime  = ptp_clock_gettime,
    .clock_getres   = ptp_clock_getres,
    .clock_settime  = ptp_clock_settime,
    .ioctl      = ptp_ioctl,
    .open       = ptp_open,
    .poll       = ptp_poll,
    .read       = ptp_read,
};

static void delete_ptp_clock(struct posix_clock *pc)
{
    struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);

    mutex_destroy(&ptp->tsevq_mux);

    /* Remove the clock from the bit map. */
    mutex_lock(&ptp_clocks_mutex);
    clear_bit(ptp->index, ptp_clocks_map);
    mutex_unlock(&ptp_clocks_mutex);

    kfree(ptp);
}

/* public interface */

struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
                     struct device *parent)
{
    struct ptp_clock *ptp;
    int err = 0, index, major = MAJOR(ptp_devt);

    if (info->n_alarm > PTP_MAX_ALARMS)
        return ERR_PTR(-EINVAL);

    /* Find a free clock slot and reserve it. */
    err = -EBUSY;
    mutex_lock(&ptp_clocks_mutex);
    index = find_first_zero_bit(ptp_clocks_map, PTP_MAX_CLOCKS);
    if (index < PTP_MAX_CLOCKS)
        set_bit(index, ptp_clocks_map);
    else
        goto no_slot;

    /* Initialize a clock structure. */
    err = -ENOMEM;
    ptp = kzalloc(sizeof(struct ptp_clock), GFP_KERNEL);
    if (ptp == NULL)
        goto no_memory;

    ptp->clock.ops = ptp_clock_ops;
    ptp->clock.release = delete_ptp_clock;
    ptp->info = info;
    ptp->devid = MKDEV(major, index);
    ptp->index = index;
    spin_lock_init(&ptp->tsevq.lock);
    mutex_init(&ptp->tsevq_mux);
    init_waitqueue_head(&ptp->tsev_wq);

    /* Create a new device in our class. */
    ptp->dev = device_create(ptp_class, parent, ptp->devid, ptp,
                 "ptp%d", ptp->index);
    if (IS_ERR(ptp->dev))
        goto no_device;

    dev_set_drvdata(ptp->dev, ptp);

    err = ptp_populate_sysfs(ptp);
    if (err)
        goto no_sysfs;

    /* Register a new PPS source. */
    if (info->pps) {
        struct pps_source_info pps;
        memset(&pps, 0, sizeof(pps));
        snprintf(pps.name, PPS_MAX_NAME_LEN, "ptp%d", index);
        pps.mode = PTP_PPS_MODE;
        pps.owner = info->owner;
        ptp->pps_source = pps_register_source(&pps, PTP_PPS_DEFAULTS);
        if (!ptp->pps_source) {
            pr_err("failed to register pps source\n");
            goto no_pps;
        }
    }

    /* Create a posix clock. */
    err = posix_clock_register(&ptp->clock, ptp->devid);
    if (err) {
        pr_err("failed to create posix clock\n");
        goto no_clock;
    }

    mutex_unlock(&ptp_clocks_mutex);
    return ptp;

no_clock:
    if (ptp->pps_source)
        pps_unregister_source(ptp->pps_source);
no_pps:
    ptp_cleanup_sysfs(ptp);
no_sysfs:
    device_destroy(ptp_class, ptp->devid);
no_device:
    mutex_destroy(&ptp->tsevq_mux);
    kfree(ptp);
no_memory:
    clear_bit(index, ptp_clocks_map);
no_slot:
    mutex_unlock(&ptp_clocks_mutex);
    return ERR_PTR(err);
}
EXPORT_SYMBOL(ptp_clock_register);

int ptp_clock_unregister(struct ptp_clock *ptp)
{
    ptp->defunct = 1;
    wake_up_interruptible(&ptp->tsev_wq);

    /* Release the clock's resources. */
    if (ptp->pps_source)
        pps_unregister_source(ptp->pps_source);
    ptp_cleanup_sysfs(ptp);
    device_destroy(ptp_class, ptp->devid);

    posix_clock_unregister(&ptp->clock);
    return 0;
}
EXPORT_SYMBOL(ptp_clock_unregister);

void ptp_clock_event(struct ptp_clock *ptp, struct ptp_clock_event *event)
{
    struct pps_event_time evt;

    switch (event->type) {

    case PTP_CLOCK_ALARM:
        break;

    case PTP_CLOCK_EXTTS:
        enqueue_external_timestamp(&ptp->tsevq, event);
        wake_up_interruptible(&ptp->tsev_wq);
        break;

    case PTP_CLOCK_PPS:
        pps_get_ts(&evt);
        pps_event(ptp->pps_source, &evt, PTP_PPS_EVENT, NULL);
        break;

    case PTP_CLOCK_PPSUSR:
        pps_event(ptp->pps_source, &event->pps_times,
              PTP_PPS_EVENT, NULL);
        break;
    }
}
EXPORT_SYMBOL(ptp_clock_event);

int ptp_clock_index(struct ptp_clock *ptp)
{
    return ptp->index;
}
EXPORT_SYMBOL(ptp_clock_index);

/* module operations */

static void __exit ptp_exit(void)
{
    class_destroy(ptp_class);
    unregister_chrdev_region(ptp_devt, PTP_MAX_CLOCKS);
}

static int __init ptp_init(void)
{
    int err;

    ptp_class = class_create(THIS_MODULE, "ptp");
    if (IS_ERR(ptp_class)) {
        pr_err("ptp: failed to allocate class\n");
        return PTR_ERR(ptp_class);
    }

    err = alloc_chrdev_region(&ptp_devt, 0, PTP_MAX_CLOCKS, "ptp");
    if (err < 0) {
        pr_err("ptp: failed to allocate device region\n");
        goto no_region;
    }

    ptp_class->dev_attrs = ptp_dev_attrs;
    pr_info("PTP clock support registered\n");
    return 0;

no_region:
    class_destroy(ptp_class);
    return err;
}

subsys_initcall(ptp_init);
module_exit(ptp_exit);

MODULE_AUTHOR("Richard Cochran <[email protected]>");
MODULE_DESCRIPTION("PTP clocks support");
MODULE_LICENSE("GPL");