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[2607:f8b0:400e:c00::243]) by gmr-mx.google.com with ESMTPS id r2si2462936pfr.0.2016.02.05.12.41.37 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 05 Feb 2016 12:41:37 -0800 (PST) Received-SPF: pass (google.com: domain of stillcompiling@gmail.com designates 2607:f8b0:400e:c00::243 as permitted sender) client-ip=2607:f8b0:400e:c00::243; Received: by mail-pf0-x243.google.com with SMTP id 71so614720pfv.1 for ; Fri, 05 Feb 2016 12:41:37 -0800 (PST) X-Received: by 10.98.1.197 with SMTP id 188mr23045192pfb.8.1454704897805; Fri, 05 Feb 2016 12:41:37 -0800 (PST) Received: from localhost.localdomain (68-185-59-186.static.knwc.wa.charter.com. [68.185.59.186]) by smtp.gmail.com with ESMTPSA id 76sm26443841pft.44.2016.02.05.12.41.36 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Fri, 05 Feb 2016 12:41:36 -0800 (PST) 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: [rtc-linux] [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> X-Original-Sender: stillcompiling@gmail.com X-Original-Authentication-Results: gmr-mx.google.com; spf=pass (google.com: domain of stillcompiling@gmail.com designates 2607:f8b0:400e:c00::243 as permitted sender) smtp.mailfrom=stillcompiling@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=NONE dis=NONE) header.from=gmail.com Reply-To: rtc-linux@googlegroups.com Precedence: list Mailing-list: list rtc-linux@googlegroups.com; contact rtc-linux+owners@googlegroups.com List-ID: X-Spam-Checked-In-Group: rtc-linux@googlegroups.com X-Google-Group-Id: 712029733259 List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , 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)