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timekeeping: Add CONFIG_HAS_PERSISTENT_CLOCK option

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Make the persistent clock check a kernel config option, so that some
platform can explicitely select it, also make CONFIG_RTC_HCTOSYS and
RTC_SYSTOHC depend on its non-existence, which could prevent the
persistent clock and RTC code from doing similar thing twice during
system's init/suspend/resume phases.

If the CONFIG_HAS_PERSISTENT_CLOCK=n, then no change happens for kernel
which still does the persistent clock check in timekeeping_init().

Cc: Thomas Gleixner <tglx@linutronix.de>
Suggested-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Feng Tang <feng.tang@intel.com>
[jstultz: Added dependency for RTC_SYSTOHC as well]
Signed-off-by: John Stultz <john.stultz@linaro.org>
This commit is contained in:
Feng Tang 2013-01-16 00:09:49 +08:00 committed by John Stultz
parent 9ecf37eb7a
commit 05ad717c77
3 changed files with 12 additions and 0 deletions
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2
drivers/rtc/Kconfig
View file

@ -20,6 +20,7 @@ if RTC_CLASS
config RTC_HCTOSYS
bool "Set system time from RTC on startup and resume"
default y
depends on !HAS_PERSISTENT_CLOCK
help
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
@ -28,6 +29,7 @@ config RTC_HCTOSYS
config RTC_SYSTOHC
bool "Set the RTC time based on NTP synchronization"
default y
depends on !HAS_PERSISTENT_CLOCK
help
If you say yes here, the system time (wall clock) will be stored
in the RTC specified by RTC_HCTOSYS_DEVICE approximately every 11

5
include/linux/time.h
View file

@ -116,10 +116,15 @@ static inline bool timespec_valid_strict(const struct timespec *ts)
}
extern bool persistent_clock_exist;
#ifdef CONFIG_HAS_PERSISTENT_CLOCK
#define has_persistent_clock() true
#else
static inline bool has_persistent_clock(void)
{
return persistent_clock_exist;
}
#endif
extern void read_persistent_clock(struct timespec *ts);
extern void read_boot_clock(struct timespec *ts);

5
kernel/time/Kconfig
View file

@ -12,6 +12,11 @@ config CLOCKSOURCE_WATCHDOG
config ARCH_CLOCKSOURCE_DATA
bool
# Platforms has a persistent clock
config HAS_PERSISTENT_CLOCK
bool
default n
# Timekeeping vsyscall support
config GENERIC_TIME_VSYSCALL
bool