Commit b3967067 authored by Joshua Clayton's avatar Joshua Clayton Committed by Alexandre Belloni

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: default avatarJoshua Clayton <stillcompiling@gmail.com>
Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@free-electrons.com>
parent 9d1fa4c3
...@@ -939,4 +939,58 @@ void rtc_timer_cancel(struct rtc_device *rtc, struct rtc_timer *timer) ...@@ -939,4 +939,58 @@ void rtc_timer_cancel(struct rtc_device *rtc, struct rtc_timer *timer)
mutex_unlock(&rtc->ops_lock); mutex_unlock(&rtc->ops_lock);
} }
/**
* rtc_read_offset - Read the amount of rtc offset in parts per billion
* @ rtc: rtc device to be used
* @ offset: the offset in parts per billion
*
* see below for details.
*
* Kernel interface to read rtc clock offset
* Returns 0 on success, or a negative number on error.
* If read_offset() is not implemented for the rtc, return -EINVAL
*/
int rtc_read_offset(struct rtc_device *rtc, long *offset)
{
int ret;
if (!rtc->ops)
return -ENODEV;
if (!rtc->ops->read_offset)
return -EINVAL;
mutex_lock(&rtc->ops_lock);
ret = rtc->ops->read_offset(rtc->dev.parent, offset);
mutex_unlock(&rtc->ops_lock);
return ret;
}
/**
* rtc_set_offset - Adjusts the duration of the average second
* @ rtc: rtc device to be used
* @ offset: the offset in parts per billion
*
* Some rtc's allow an adjustment to the average duration of a second
* to compensate for differences in the actual clock rate due to temperature,
* the crystal, capacitor, etc.
*
* Kernel interface to adjust an rtc clock offset.
* Return 0 on success, or a negative number on error.
* If the rtc offset is not setable (or not implemented), return -EINVAL
*/
int rtc_set_offset(struct rtc_device *rtc, long offset)
{
int ret;
if (!rtc->ops)
return -ENODEV;
if (!rtc->ops->set_offset)
return -EINVAL;
mutex_lock(&rtc->ops_lock);
ret = rtc->ops->set_offset(rtc->dev.parent, offset);
mutex_unlock(&rtc->ops_lock);
return ret;
}
...@@ -89,6 +89,8 @@ struct rtc_class_ops { ...@@ -89,6 +89,8 @@ struct rtc_class_ops {
int (*set_mmss)(struct device *, unsigned long secs); int (*set_mmss)(struct device *, unsigned long secs);
int (*read_callback)(struct device *, int data); int (*read_callback)(struct device *, int data);
int (*alarm_irq_enable)(struct device *, unsigned int enabled); 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 #define RTC_DEVICE_NAME_SIZE 20
...@@ -208,6 +210,8 @@ void rtc_timer_init(struct rtc_timer *timer, void (*f)(void *p), void *data); ...@@ -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, int rtc_timer_start(struct rtc_device *rtc, struct rtc_timer *timer,
ktime_t expires, ktime_t period); ktime_t expires, ktime_t period);
void rtc_timer_cancel(struct rtc_device *rtc, struct rtc_timer *timer); 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); void rtc_timer_do_work(struct work_struct *work);
static inline bool is_leap_year(unsigned int year) static inline bool is_leap_year(unsigned int year)
......
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