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authorDavid Brownell <david-b@pacbell.net>2007-11-14 19:58:29 -0500
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-11-14 21:45:36 -0500
commit779d20892f8e716677194dc879eea2b5f1e75678 (patch)
treea520bb7e98dd09c312d8a9f94ef1058a15543ffe
parent1299342bacbe9038bef473d9b5b3cbebad112d4c (diff)
rtc_hctosys expects RTCs in UTC (doc)
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>
-rw-r--r--drivers/rtc/Kconfig4
-rw-r--r--drivers/rtc/hctosys.c4
2 files changed, 5 insertions, 3 deletions
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index cbde770eb121..7958635f12cc 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -36,7 +36,9 @@ config RTC_HCTOSYS_DEVICE
36 help 36 help
37 The RTC device that will be used to (re)initialize the system 37 The RTC device that will be used to (re)initialize the system
38 clock, usually rtc0. Initialization is done when the system 38 clock, usually rtc0. Initialization is done when the system
39 starts up, and when it resumes from a low power state. 39 starts up, and when it resumes from a low power state. This
40 device should record time in UTC, since the kernel won't do
41 timezone correction.
40 42
41 The driver for this RTC device must be loaded before late_initcall 43 The driver for this RTC device must be loaded before late_initcall
42 functions run, so it must usually be statically linked. 44 functions run, so it must usually be statically linked.
diff --git a/drivers/rtc/hctosys.c b/drivers/rtc/hctosys.c
index 178527252c6a..33c0e98243ee 100644
--- a/drivers/rtc/hctosys.c
+++ b/drivers/rtc/hctosys.c
@@ -47,8 +47,8 @@ static int __init rtc_hctosys(void)
47 do_settimeofday(&tv); 47 do_settimeofday(&tv);
48 48
49 dev_info(rtc->dev.parent, 49 dev_info(rtc->dev.parent,
50 "setting the system clock to " 50 "setting system clock to "
51 "%d-%02d-%02d %02d:%02d:%02d (%u)\n", 51 "%d-%02d-%02d %02d:%02d:%02d UTC (%u)\n",
52 tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, 52 tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
53 tm.tm_hour, tm.tm_min, tm.tm_sec, 53 tm.tm_hour, tm.tm_min, tm.tm_sec,
54 (unsigned int) tv.tv_sec); 54 (unsigned int) tv.tv_sec);