diff options
Diffstat (limited to 'drivers/rtc/hctosys.c')
-rw-r--r-- | drivers/rtc/hctosys.c | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/drivers/rtc/hctosys.c b/drivers/rtc/hctosys.c new file mode 100644 index 00000000000..d02fe9a0001 --- /dev/null +++ b/drivers/rtc/hctosys.c @@ -0,0 +1,69 @@ +/* + * 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. +*/ + +#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. + */ + +static int __init rtc_hctosys(void) +{ + int err; + struct rtc_time tm; + struct class_device *class_dev = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE); + + if (class_dev == NULL) { + printk("%s: unable to open rtc device (%s)\n", + __FILE__, CONFIG_RTC_HCTOSYS_DEVICE); + return -ENODEV; + } + + err = rtc_read_time(class_dev, &tm); + if (err == 0) { + err = rtc_valid_tm(&tm); + if (err == 0) { + struct timespec tv; + + tv.tv_nsec = NSEC_PER_SEC >> 1; + + rtc_tm_to_time(&tm, &tv.tv_sec); + + do_settimeofday(&tv); + + dev_info(class_dev->dev, + "setting the system clock to " + "%d-%02d-%02d %02d:%02d:%02d (%u)\n", + tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, + tm.tm_hour, tm.tm_min, tm.tm_sec, + (unsigned int) tv.tv_sec); + } + else + dev_err(class_dev->dev, + "hctosys: invalid date/time\n"); + } + else + dev_err(class_dev->dev, + "hctosys: unable to read the hardware clock\n"); + + rtc_class_close(class_dev); + + return 0; +} + +late_initcall(rtc_hctosys); |