/*
|
* RTC subsystem, initialize system time on startup
|
*
|
* Copyright (C) 2005 Tower Technologies
|
* Author: Alessandro Zummo <a.zummo@towertech.it>
|
*
|
* 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/rtc.h>
|
|
/* IMPORTANT: the RTC only stores whole seconds. It is arbitrary
|
* whether it stores the most close value or the value with partial
|
* seconds truncated. However, it is important that we use it to store
|
* the truncated value. This is because otherwise it is necessary,
|
* in an rtc sync function, to read both xtime.tv_sec and
|
* xtime.tv_nsec. On some processors (i.e. ARM), an atomic read
|
* of >32bits is not possible. So storing the most close value would
|
* slow down the sync API. So here we have the truncated value and
|
* the best guess is to add 0.5s.
|
*/
|
|
int rtc_hctosys(void)
|
{
|
int err = -ENODEV;
|
struct rtc_time tm;
|
struct timespec64 tv64 = {
|
.tv_nsec = NSEC_PER_SEC >> 1,
|
};
|
struct rtc_device *rtc = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE);
|
|
if (rtc == NULL) {
|
pr_info("unable to open rtc device (%s)\n",
|
CONFIG_RTC_HCTOSYS_DEVICE);
|
goto err_open;
|
}
|
|
err = rtc_read_time(rtc, &tm);
|
if (err) {
|
dev_err(rtc->dev.parent,
|
"hctosys: unable to read the hardware clock\n");
|
goto err_read;
|
|
}
|
|
tv64.tv_sec = rtc_tm_to_time64(&tm);
|
|
#if BITS_PER_LONG == 32
|
if (tv64.tv_sec > INT_MAX) {
|
err = -ERANGE;
|
goto err_read;
|
}
|
#endif
|
|
err = do_settimeofday64(&tv64);
|
|
dev_info(rtc->dev.parent,
|
"setting system clock to "
|
"%d-%02d-%02d %02d:%02d:%02d UTC (%lld)\n",
|
tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
|
tm.tm_hour, tm.tm_min, tm.tm_sec,
|
(long long) tv64.tv_sec);
|
|
err_read:
|
rtc_class_close(rtc);
|
|
err_open:
|
rtc_hctosys_ret = err;
|
|
return err;
|
}
|
