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; 28 struct rtc_time tm; 29 struct rtc_device *rtc = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE); 30 31 if (rtc == NULL) { 32 printk("%s: unable to open rtc device (%s)\n", 33 __FILE__, CONFIG_RTC_HCTOSYS_DEVICE); 34 return -ENODEV; 35 } 36 37 err = rtc_read_time(rtc, &tm); 38 if (err == 0) { 39 err = rtc_valid_tm(&tm); 40 if (err == 0) { 41 struct timespec tv; 42 43 tv.tv_nsec = NSEC_PER_SEC >> 1; 44 45 rtc_tm_to_time(&tm, &tv.tv_sec); 46 47 do_settimeofday(&tv); 48 49 dev_info(rtc->dev.parent, 50 "setting the system clock to " 51 "%d-%02d-%02d %02d:%02d:%02d (%u)\n", 52 tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, 53 tm.tm_hour, tm.tm_min, tm.tm_sec, 54 (unsigned int) tv.tv_sec); 55 } 56 else 57 dev_err(rtc->dev.parent, 58 "hctosys: invalid date/time\n"); 59 } 60 else 61 dev_err(rtc->dev.parent, 62 "hctosys: unable to read the hardware clock\n"); 63 64 rtc_class_close(rtc); 65 66 return 0; 67} 68 69late_initcall(rtc_hctosys); 70