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 25int rtc_hctosys_ret = -ENODEV; 26 27static int __init rtc_hctosys(void) 28{ 29 int err = -ENODEV; 30 struct rtc_time tm; 31 struct timespec tv = { 32 .tv_nsec = NSEC_PER_SEC >> 1, 33 }; 34 struct rtc_device *rtc = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE); 35 36 if (rtc == NULL) { 37 pr_err("%s: unable to open rtc device (%s)\n", 38 __FILE__, CONFIG_RTC_HCTOSYS_DEVICE); 39 goto err_open; 40 } 41 42 err = rtc_read_time(rtc, &tm); 43 if (err) { 44 dev_err(rtc->dev.parent, 45 "hctosys: unable to read the hardware clock\n"); 46 goto err_read; 47 48 } 49 50 err = rtc_valid_tm(&tm); 51 if (err) { 52 dev_err(rtc->dev.parent, 53 "hctosys: invalid date/time\n"); 54 goto err_invalid; 55 } 56 57 rtc_tm_to_time(&tm, &tv.tv_sec); 58 59 do_settimeofday(&tv); 60 61 dev_info(rtc->dev.parent, 62 "setting system clock to " 63 "%d-%02d-%02d %02d:%02d:%02d UTC (%u)\n", 64 tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, 65 tm.tm_hour, tm.tm_min, tm.tm_sec, 66 (unsigned int) tv.tv_sec); 67 68err_invalid: 69err_read: 70 rtc_class_close(rtc); 71 72err_open: 73 rtc_hctosys_ret = err; 74 75 return err; 76} 77 78late_initcall(rtc_hctosys); 79