[go: nahoru, domu]
1/*
2 * RTC subsystem, initialize system time on startup
3 *
4 * Copyright (C) 2005 Tower Technologies
5 * Author: Alessandro Zummo <a.zummo@towertech.it>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10*/
11
12#include <linux/rtc.h>
13
14/* IMPORTANT: the RTC only stores whole seconds. It is arbitrary
15 * whether it stores the most close value or the value with partial
16 * seconds truncated. However, it is important that we use it to store
17 * the truncated value. This is because otherwise it is necessary,
18 * in an rtc sync function, to read both xtime.tv_sec and
19 * xtime.tv_nsec. On some processors (i.e. ARM), an atomic read
20 * of >32bits is not possible. So storing the most close value would
21 * slow down the sync API. So here we have the truncated value and
22 * the best guess is to add 0.5s.
23 */
24
25static int __init rtc_hctosys(void)
26{
27	int err = -ENODEV;
28	struct rtc_time tm;
29	struct timespec tv = {
30		.tv_nsec = NSEC_PER_SEC >> 1,
31	};
32	struct rtc_device *rtc = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE);
33
34	if (rtc == NULL) {
35		pr_err("%s: unable to open rtc device (%s)\n",
36			__FILE__, CONFIG_RTC_HCTOSYS_DEVICE);
37		goto err_open;
38	}
39
40	err = rtc_read_time(rtc, &tm);
41	if (err) {
42		dev_err(rtc->dev.parent,
43			"hctosys: unable to read the hardware clock\n");
44		goto err_read;
45
46	}
47
48	err = rtc_valid_tm(&tm);
49	if (err) {
50		dev_err(rtc->dev.parent,
51			"hctosys: invalid date/time\n");
52		goto err_invalid;
53	}
54
55	rtc_tm_to_time(&tm, &tv.tv_sec);
56
57	err = do_settimeofday(&tv);
58
59	dev_info(rtc->dev.parent,
60		"setting system clock to "
61		"%d-%02d-%02d %02d:%02d:%02d UTC (%u)\n",
62		tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
63		tm.tm_hour, tm.tm_min, tm.tm_sec,
64		(unsigned int) tv.tv_sec);
65
66err_invalid:
67err_read:
68	rtc_class_close(rtc);
69
70err_open:
71	rtc_hctosys_ret = err;
72
73	return err;
74}
75
76late_initcall(rtc_hctosys);
77