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

5
include/linux/time.h
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@ -116,10 +116,15 @@ static inline bool timespec_valid_strict(const struct timespec *ts)
} }
extern bool persistent_clock_exist; extern bool persistent_clock_exist;
#ifdef CONFIG_HAS_PERSISTENT_CLOCK
#define has_persistent_clock() true
#else
static inline bool has_persistent_clock(void) static inline bool has_persistent_clock(void)
{ {
return persistent_clock_exist; return persistent_clock_exist;
} }
#endif
extern void read_persistent_clock(struct timespec *ts); extern void read_persistent_clock(struct timespec *ts);
extern void read_boot_clock(struct timespec *ts); extern void read_boot_clock(struct timespec *ts);

5
kernel/time/Kconfig
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@ -12,6 +12,11 @@ config CLOCKSOURCE_WATCHDOG
config ARCH_CLOCKSOURCE_DATA config ARCH_CLOCKSOURCE_DATA
bool bool
# Platforms has a persistent clock
config HAS_PERSISTENT_CLOCK
bool
default n
# Timekeeping vsyscall support # Timekeeping vsyscall support
config GENERIC_TIME_VSYSCALL config GENERIC_TIME_VSYSCALL
bool bool