From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756046AbcBEUll (ORCPT ); Fri, 5 Feb 2016 15:41:41 -0500 Received: from mail-pf0-f196.google.com ([209.85.192.196]:36418 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753926AbcBEUli (ORCPT ); Fri, 5 Feb 2016 15:41:38 -0500 From: Joshua Clayton To: Alessandro Zummo , Alexandre Belloni Cc: Jonathan Corbet , rtc-linux@googlegroups.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Joshua Clayton Subject: [PATCH v4 1/3] rtc: Add functions to set and read rtc offset Date: Fri, 5 Feb 2016 12:41:11 -0800 Message-Id: <1454704873-31066-1-git-send-email-stillcompiling@gmail.com> X-Mailer: git-send-email 2.5.0 In-Reply-To: <20160205143908.GJ4782@piout.net> References: <20160205143908.GJ4782@piout.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- drivers/rtc/interface.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/rtc.h | 4 ++++ 2 files changed, 58 insertions(+) diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c index 5836751..9ef5f6f 100644 --- a/drivers/rtc/interface.c +++ b/drivers/rtc/interface.c @@ -939,4 +939,58 @@ void rtc_timer_cancel(struct rtc_device *rtc, struct rtc_timer *timer) 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; +} diff --git a/include/linux/rtc.h b/include/linux/rtc.h index 3359f04..b693ada 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) -- 2.5.0