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| author |   Joshua Clayton <stillcompiling@gmail.com> | 2016-02-05 12:41:11 -0800 |
|---|---|---|
| committer |   Alexandre Belloni <alexandre.belloni@free-electrons.com> | 2016-03-14 17:08:15 +0100 |
| commit | b3967067c273359c7462f4be9a887c3d1a515f49 (patch) | |
| tree | 1f2ca90d34dae4961b97d68ccdb93a979ee5e2b8 /include/linux/rtc.h | |
| parent | rtc: rv8803: convert spin_lock to mutex_lock (diff) | |
| download | wireguard-linux-b3967067c273359c7462f4be9a887c3d1a515f49.tar.xz wireguard-linux-b3967067c273359c7462f4be9a887c3d1a515f49.zip | |
rtc: Add functions to set and read rtc offset
A number of rtc devices, such as the NXP pcf2123 include a facility
to adjust the clock in order to compensate for temperature or a
crystal, capacitor, etc, that results in the rtc clock not running
at exactly 32.768 kHz.
Data sheets I have seen refer to this as a clock offset, and measure it
in parts per million, however they often reference ppm to 2 digits of
precision, which makes integer ppm less than ideal.
We use parts per billion, which more than covers the precision needed
and works nicely within 32 bits
Signed-off-by: Joshua Clayton <stillcompiling@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Diffstat (limited to 'include/linux/rtc.h')
| -rw-r--r-- | include/linux/rtc.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/rtc.h b/include/linux/rtc.h index 3359f0422c6b..b693adac853b 100644 --- a/include/linux/rtc.h +++ b/include/linux/rtc.h @@ -89,6 +89,8 @@ struct rtc_class_ops { int (*set_mmss)(struct device *, unsigned long secs); int (*read_callback)(struct device *, int data); int (*alarm_irq_enable)(struct device *, unsigned int enabled); + int (*read_offset)(struct device *, long *offset); + int (*set_offset)(struct device *, long offset); }; #define RTC_DEVICE_NAME_SIZE 20 @@ -208,6 +210,8 @@ void rtc_timer_init(struct rtc_timer *timer, void (*f)(void *p), void *data); int rtc_timer_start(struct rtc_device *rtc, struct rtc_timer *timer, ktime_t expires, ktime_t period); void rtc_timer_cancel(struct rtc_device *rtc, struct rtc_timer *timer); +int rtc_read_offset(struct rtc_device *rtc, long *offset); +int rtc_set_offset(struct rtc_device *rtc, long offset); void rtc_timer_do_work(struct work_struct *work); static inline bool is_leap_year(unsigned int year) |