779d20892f
The RTC "hctosys" mechanism expects that RTC clock will use UTC, not local time (e.g. PST). Say so in Kconfig and in the kernel message. (Strictly speaking, the RTC clock should be tracking the POSIX epoch. That's not worth going into here. Goofing timezones means clocks are wrong by many hours; the POSIX-v-UTC differences just cost seconds.) Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Acked-by: Alessandro Zummo <a.zummo@towertech.it> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
70 lines
1.8 KiB
C
70 lines
1.8 KiB
C
/*
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* RTC subsystem, initialize system time on startup
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*
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* Copyright (C) 2005 Tower Technologies
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* Author: Alessandro Zummo <a.zummo@towertech.it>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/rtc.h>
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/* IMPORTANT: the RTC only stores whole seconds. It is arbitrary
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* whether it stores the most close value or the value with partial
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* seconds truncated. However, it is important that we use it to store
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* the truncated value. This is because otherwise it is necessary,
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* in an rtc sync function, to read both xtime.tv_sec and
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* xtime.tv_nsec. On some processors (i.e. ARM), an atomic read
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* of >32bits is not possible. So storing the most close value would
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* slow down the sync API. So here we have the truncated value and
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* the best guess is to add 0.5s.
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*/
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static int __init rtc_hctosys(void)
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{
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int err;
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struct rtc_time tm;
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struct rtc_device *rtc = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE);
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if (rtc == NULL) {
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printk("%s: unable to open rtc device (%s)\n",
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__FILE__, CONFIG_RTC_HCTOSYS_DEVICE);
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return -ENODEV;
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}
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err = rtc_read_time(rtc, &tm);
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if (err == 0) {
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err = rtc_valid_tm(&tm);
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if (err == 0) {
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struct timespec tv;
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tv.tv_nsec = NSEC_PER_SEC >> 1;
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rtc_tm_to_time(&tm, &tv.tv_sec);
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do_settimeofday(&tv);
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dev_info(rtc->dev.parent,
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"setting system clock to "
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"%d-%02d-%02d %02d:%02d:%02d UTC (%u)\n",
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tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
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tm.tm_hour, tm.tm_min, tm.tm_sec,
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(unsigned int) tv.tv_sec);
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}
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else
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dev_err(rtc->dev.parent,
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"hctosys: invalid date/time\n");
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}
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else
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dev_err(rtc->dev.parent,
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"hctosys: unable to read the hardware clock\n");
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rtc_class_close(rtc);
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return 0;
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}
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late_initcall(rtc_hctosys);
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