| Alessandro Zummo | 0c86edc | 2006-03-27 01:16:37 -0800 | [diff] [blame] | 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 | |
| 25 | static int __init rtc_hctosys(void) |
| 26 | { |
| 27 | int err; |
| 28 | struct rtc_time tm; |
| 29 | struct class_device *class_dev = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE); |
| 30 | |
| 31 | if (class_dev == 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(class_dev, &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(class_dev->dev, |
| 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(class_dev->dev, |
| 58 | "hctosys: invalid date/time\n"); |
| 59 | } |
| 60 | else |
| 61 | dev_err(class_dev->dev, |
| 62 | "hctosys: unable to read the hardware clock\n"); |
| 63 | |
| 64 | rtc_class_close(class_dev); |
| 65 | |
| 66 | return 0; |
| 67 | } |
| 68 | |
| 69 | late_initcall(rtc_hctosys); |