diff options
| author | David Brownell <david-b@pacbell.net> | 2007-05-08 00:33:42 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-05-08 11:15:18 -0700 |
| commit | 7ca1d488ffe4817adaba61cc05b972782f7d3f91 (patch) | |
| tree | 97fee4d2ddbc5be5265d99f5825e902f7a9262c1 /drivers/rtc/Kconfig | |
| parent | cd9662094edf4173e87f0452e57e4eacc228f8ff (diff) | |
rtc: suspend()/resume() restores system clock
RTC class suspend/resume support, re-initializing the system clock on resume
from the clock used to initialize it at boot time.
- The reinit-on-resume is hooked to the existing RTC_HCTOSYS config
option, on the grounds that a clock good enough for init must also
be good enough for re-init.
- Inlining a version of the code used by ARM, to save and restore the
delta between a selected RTC and the current system wall-clock time.
- Removes calls to that ARM code from AT91, OMAP1, and S3C RTCs. This
means that systems using those RTCs across suspend/resume will likely
want to change their kernel configs to enable RTC_HCTOSYS.
If HCTOSYS isn't using a second RTC (with battery?), this changes the
system's initial date from Jan 1970 to the epoch this hardware uses:
1998 for AT91, 2000 for OMAP1 (assuming no split power mode), etc.
This goes on top of the patch series removing "struct class_device" usage
from the RTC framework. That's all needed for class suspend()/resume().
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
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>
Diffstat (limited to 'drivers/rtc/Kconfig')
| -rw-r--r-- | drivers/rtc/Kconfig | 24 |
1 files changed, 17 insertions, 7 deletions
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig index ec33ee87735..a53ef4d670c 100644 --- a/drivers/rtc/Kconfig +++ b/drivers/rtc/Kconfig @@ -21,21 +21,31 @@ config RTC_CLASS will be called rtc-class. config RTC_HCTOSYS - bool "Set system time from RTC on startup" + bool "Set system time from RTC on startup and resume" depends on RTC_CLASS = y default y help - If you say yes here, the system time will be set using - the value read from the specified RTC device. This is useful - in order to avoid unnecessary fsck runs. + If you say yes here, the system time (wall clock) will be set using + the value read from a specified RTC device. This is useful to avoid + unnecessary fsck runs at boot time, and to network better. config RTC_HCTOSYS_DEVICE - string "The RTC to read the time from" + string "RTC used to set the system time" depends on RTC_HCTOSYS = y default "rtc0" help - The RTC device that will be used as the source for - the system time, usually rtc0. + The RTC device that will be used to (re)initialize the system + clock, usually rtc0. Initialization is done when the system + starts up, and when it resumes from a low power state. + + This clock should be battery-backed, so that it reads the correct + time when the system boots from a power-off state. Otherwise, your + system will need an external clock source (like an NTP server). + + If the clock you specify here is not battery backed, it may still + be useful to reinitialize system time when resuming from system + sleep states. Do not specify an RTC here unless it stays powered + during all this system's supported sleep states. config RTC_DEBUG bool "RTC debug support" |