linux-imx

/*

 * RTC subsystem, base class

 *

 * Copyright (C) 2005 Tower Technologies

 * Author: Alessandro Zummo <a.zummo@towertech.it>

 *

 * class skeleton from drivers/hwmon/hwmon.c

 *

 * 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.

*/

​

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

​

#include <linux/module.h>

#include <linux/of.h>

#include <linux/rtc.h>

#include <linux/kdev_t.h>

#include <linux/idr.h>

#include <linux/slab.h>

#include <linux/workqueue.h>

​

#include "rtc-core.h"

​

​

static DEFINE_IDA(rtc_ida);

struct class *rtc_class;

​

static void rtc_device_release(struct device *dev)

{

    struct rtc_device *rtc = to_rtc_device(dev);

    ida_simple_remove(&rtc_ida, rtc->id);

    kfree(rtc);

}

​

#ifdef CONFIG_RTC_HCTOSYS_DEVICE

/* Result of the last RTC to system clock attempt. */

int rtc_hctosys_ret = -ENODEV;

#endif

​

#if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)

/*

 * On suspend(), measure the delta between one RTC and the

 * system's wall clock; restore it on resume().

 */

​

static struct timespec64 old_rtc, old_system, old_delta;

​

​

static int rtc_suspend(struct device *dev)

{

    struct rtc_device   *rtc = to_rtc_device(dev);

    struct rtc_time     tm;

    struct timespec64   delta, delta_delta;

    int err;

​

    if (timekeeping_rtc_skipsuspend())

        return 0;

​

    if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)

        return 0;

​

    /* snapshot the current RTC and system time at suspend*/

    err = rtc_read_time(rtc, &tm);

    if (err < 0) {

        pr_debug("%s:  fail to read rtc time\n", dev_name(&rtc->dev));

        return 0;

    }

​

    ktime_get_real_ts64(&old_system);

    old_rtc.tv_sec = rtc_tm_to_time64(&tm);

​

​

    /*

     * To avoid drift caused by repeated suspend/resumes,

     * which each can add ~1 second drift error,

     * try to compensate so the difference in system time

     * and rtc time stays close to constant.

     */

    delta = timespec64_sub(old_system, old_rtc);

    delta_delta = timespec64_sub(delta, old_delta);

    if (delta_delta.tv_sec < -2 || delta_delta.tv_sec >= 2) {

        /*

         * if delta_delta is too large, assume time correction

         * has occured and set old_delta to the current delta.

         */

        old_delta = delta;

    } else {

        /* Otherwise try to adjust old_system to compensate */

        old_system = timespec64_sub(old_system, delta_delta);

    }