From: Joshua Clayton <stillcompiling@gmail.com> To: Alexandre Belloni <alexandre.belloni@free-electrons.com>, Alessandro Zummo <a.zummo@towertech.it> Cc: rtc-linux@googlegroups.com, linux-kernel@vger.kernel.org, Joshua Clayton <stillcompiling@gmail.com> Subject: [PATCH v3 3/3] rtc-pcf2123: implement read_offset and set_offset Date: Wed, 3 Feb 2016 09:16:44 -0800 [thread overview] Message-ID: <1454519804-13770-3-git-send-email-stillcompiling@gmail.com> (raw) In-Reply-To: <1454519804-13770-1-git-send-email-stillcompiling@gmail.com> In-Reply-To: <20160202104111.GU20165@piout.net> pcf2123 has an offset register, which can be used to make minor adjustments to the clock rate to compensate for temperature or a crystal that is not exactly right. Signed-off-by: Joshua Clayton <stillcompiling@gmail.com> --- drivers/rtc/rtc-pcf2123.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) diff --git a/drivers/rtc/rtc-pcf2123.c b/drivers/rtc/rtc-pcf2123.c index d9a44ad..da27738 100644 --- a/drivers/rtc/rtc-pcf2123.c +++ b/drivers/rtc/rtc-pcf2123.c @@ -100,6 +100,7 @@ /* PCF2123_REG_OFFSET BITS */ #define OFFSET_SIGN_BIT BIT(6) /* 2's complement sign bit */ #define OFFSET_COARSE BIT(7) /* Coarse mode offset */ +#define OFFSET_STEP (2170) /* Offset step in parts per billion */ /* READ/WRITE ADDRESS BITS */ #define PCF2123_WRITE BIT(4) @@ -206,6 +207,59 @@ static ssize_t pcf2123_store(struct device *dev, struct device_attribute *attr, return count; } +static int pcf2123_read_offset(struct device *dev, long *offset) +{ + int ret; + s8 reg; + + ret = pcf2123_read(dev, PCF2123_REG_OFFSET, ®, 1); + if (ret < 0) + return ret; + + if (reg & OFFSET_COARSE) + reg <<= 1; /* multiply by 2 and sign extend */ + else + reg |= (reg & OFFSET_SIGN_BIT) << 1; /* sign extend only */ + + *offset = ((long)reg) * OFFSET_STEP; + + return 0; +} + +/* + * The offset register is a 7 bit signed value with a coarse bit in bit 7. + * The main difference between the two is normal offset adjusts the first + * second of n minutes every other hour, with 61, 62 and 63 being shoved + * into the 60th minute. + * The coarse adjustment does the same, but every hour. + * the two overlap, with every even normal offset value corresponding + * to a coarse offset. Based on this algorithm, it seems that despite the + * name, coarse offset is a better fit for overlapping values. + */ +static int pcf2123_set_offset(struct device *dev, long offset) +{ + s8 reg; + + if (offset > OFFSET_STEP * 127) + reg = 127; + else if (offset < OFFSET_STEP * -128) + reg = -128; + else + reg = (s8)((offset + (OFFSET_STEP >> 1)) / OFFSET_STEP); + + /* choose fine offset only for odd values in the normal range */ + if (reg & 1 && reg <= 63 && reg >= -64) { + /* Normal offset. Clear the coarse bit */ + reg &= ~OFFSET_COARSE; + } else { + /* Coarse offset. Divide by 2 and set the coarse bit */ + reg >>= 1; + reg |= OFFSET_COARSE; + } + + return pcf2123_write_reg(dev, PCF2123_REG_OFFSET, reg); +} + static int pcf2123_rtc_read_time(struct device *dev, struct rtc_time *tm) { u8 rxbuf[7]; @@ -314,6 +368,9 @@ static int pcf2123_reset(struct device *dev) static const struct rtc_class_ops pcf2123_rtc_ops = { .read_time = pcf2123_rtc_read_time, .set_time = pcf2123_rtc_set_time, + .read_offset = pcf2123_read_offset, + .set_offset = pcf2123_set_offset, + }; static int pcf2123_probe(struct spi_device *spi) -- 2.5.0
WARNING: multiple messages have this Message-ID (diff)
From: Joshua Clayton <stillcompiling@gmail.com> To: Alexandre Belloni <alexandre.belloni@free-electrons.com>, Alessandro Zummo <a.zummo@towertech.it> Cc: rtc-linux@googlegroups.com, linux-kernel@vger.kernel.org, Joshua Clayton <stillcompiling@gmail.com> Subject: [rtc-linux] [PATCH v3 3/3] rtc-pcf2123: implement read_offset and set_offset Date: Wed, 3 Feb 2016 09:16:44 -0800 [thread overview] Message-ID: <1454519804-13770-3-git-send-email-stillcompiling@gmail.com> (raw) In-Reply-To: <1454519804-13770-1-git-send-email-stillcompiling@gmail.com> In-Reply-To: <20160202104111.GU20165@piout.net> pcf2123 has an offset register, which can be used to make minor adjustments to the clock rate to compensate for temperature or a crystal that is not exactly right. Signed-off-by: Joshua Clayton <stillcompiling@gmail.com> --- drivers/rtc/rtc-pcf2123.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) diff --git a/drivers/rtc/rtc-pcf2123.c b/drivers/rtc/rtc-pcf2123.c index d9a44ad..da27738 100644 --- a/drivers/rtc/rtc-pcf2123.c +++ b/drivers/rtc/rtc-pcf2123.c @@ -100,6 +100,7 @@ /* PCF2123_REG_OFFSET BITS */ #define OFFSET_SIGN_BIT BIT(6) /* 2's complement sign bit */ #define OFFSET_COARSE BIT(7) /* Coarse mode offset */ +#define OFFSET_STEP (2170) /* Offset step in parts per billion */ /* READ/WRITE ADDRESS BITS */ #define PCF2123_WRITE BIT(4) @@ -206,6 +207,59 @@ static ssize_t pcf2123_store(struct device *dev, struct device_attribute *attr, return count; } +static int pcf2123_read_offset(struct device *dev, long *offset) +{ + int ret; + s8 reg; + + ret = pcf2123_read(dev, PCF2123_REG_OFFSET, ®, 1); + if (ret < 0) + return ret; + + if (reg & OFFSET_COARSE) + reg <<= 1; /* multiply by 2 and sign extend */ + else + reg |= (reg & OFFSET_SIGN_BIT) << 1; /* sign extend only */ + + *offset = ((long)reg) * OFFSET_STEP; + + return 0; +} + +/* + * The offset register is a 7 bit signed value with a coarse bit in bit 7. + * The main difference between the two is normal offset adjusts the first + * second of n minutes every other hour, with 61, 62 and 63 being shoved + * into the 60th minute. + * The coarse adjustment does the same, but every hour. + * the two overlap, with every even normal offset value corresponding + * to a coarse offset. Based on this algorithm, it seems that despite the + * name, coarse offset is a better fit for overlapping values. + */ +static int pcf2123_set_offset(struct device *dev, long offset) +{ + s8 reg; + + if (offset > OFFSET_STEP * 127) + reg = 127; + else if (offset < OFFSET_STEP * -128) + reg = -128; + else + reg = (s8)((offset + (OFFSET_STEP >> 1)) / OFFSET_STEP); + + /* choose fine offset only for odd values in the normal range */ + if (reg & 1 && reg <= 63 && reg >= -64) { + /* Normal offset. Clear the coarse bit */ + reg &= ~OFFSET_COARSE; + } else { + /* Coarse offset. Divide by 2 and set the coarse bit */ + reg >>= 1; + reg |= OFFSET_COARSE; + } + + return pcf2123_write_reg(dev, PCF2123_REG_OFFSET, reg); +} + static int pcf2123_rtc_read_time(struct device *dev, struct rtc_time *tm) { u8 rxbuf[7]; @@ -314,6 +368,9 @@ static int pcf2123_reset(struct device *dev) static const struct rtc_class_ops pcf2123_rtc_ops = { .read_time = pcf2123_rtc_read_time, .set_time = pcf2123_rtc_set_time, + .read_offset = pcf2123_read_offset, + .set_offset = pcf2123_set_offset, + }; static int pcf2123_probe(struct spi_device *spi) -- 2.5.0 -- -- You received this message because you are subscribed to "rtc-linux". Membership options at http://groups.google.com/group/rtc-linux . Please read http://groups.google.com/group/rtc-linux/web/checklist before submitting a driver. --- You received this message because you are subscribed to the Google Groups "rtc-linux" group. To unsubscribe from this group and stop receiving emails from it, send an email to rtc-linux+unsubscribe@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
next prev parent reply other threads:[~2016-02-03 17:17 UTC|newest] Thread overview: 85+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-01-04 18:31 [PATCH v2 0/8] rtc: enable adjustment of clock offset Joshua Clayton 2016-01-04 18:31 ` [rtc-linux] " Joshua Clayton [not found] ` <0000-cover-letter.patch> 2016-01-04 18:31 ` [PATCH v2 1/8] rtc-pcf2123: define registers and bit macros Joshua Clayton 2016-01-04 18:31 ` [rtc-linux] " Joshua Clayton 2016-01-04 18:31 ` [PATCH v2 2/8] rtc-pcf2123: clean up reads from the chip Joshua Clayton 2016-01-04 18:31 ` [rtc-linux] " Joshua Clayton 2016-01-04 18:31 ` [PATCH v2 3/8] rtc-pcf2123: clean up writes to the rtc chip Joshua Clayton 2016-01-04 18:31 ` [rtc-linux] " Joshua Clayton 2016-01-04 18:31 ` [PATCH v2 4/8] rtc-pcf2123: refactor chip reset into a function Joshua Clayton 2016-01-04 18:31 ` [rtc-linux] " Joshua Clayton 2016-01-04 18:31 ` [PATCH v2 5/8] rtc-pcf2123: avoid resetting the clock if possible Joshua Clayton 2016-01-04 18:31 ` [rtc-linux] " Joshua Clayton 2016-01-04 18:31 ` [PATCH v2 6/8] rtc: Add functions to set and read clock offset Joshua Clayton 2016-01-04 18:31 ` [rtc-linux] " Joshua Clayton 2016-01-04 18:31 ` [PATCH v2 7/8] rtc: implement a sysfs interface for " Joshua Clayton 2016-01-04 18:31 ` [rtc-linux] " Joshua Clayton 2016-01-31 11:41 ` Alexandre Belloni 2016-01-31 11:41 ` [rtc-linux] " Alexandre Belloni 2016-02-01 20:56 ` Joshua Clayton 2016-02-01 20:56 ` [rtc-linux] " Joshua Clayton 2016-02-02 10:41 ` Alexandre Belloni 2016-02-02 10:41 ` [rtc-linux] " Alexandre Belloni 2016-02-03 17:16 ` [PATCH v3 1/3] rtc: Add functions to set and read rtc offset Joshua Clayton 2016-02-03 17:16 ` [rtc-linux] " Joshua Clayton 2016-02-04 22:07 ` Alexandre Belloni 2016-02-04 22:07 ` [rtc-linux] " Alexandre Belloni 2016-02-04 23:32 ` Joshua Clayton 2016-02-04 23:32 ` [rtc-linux] " Joshua Clayton 2016-02-05 14:39 ` Alexandre Belloni 2016-02-05 14:39 ` [rtc-linux] " Alexandre Belloni 2016-02-05 20:41 ` [PATCH v4 " Joshua Clayton 2016-02-05 20:41 ` [rtc-linux] " Joshua Clayton 2016-02-05 20:41 ` [PATCH v4 2/3] rtc: implement a sysfs interface for clock offset Joshua Clayton 2016-02-05 20:41 ` [rtc-linux] " Joshua Clayton 2016-02-05 20:41 ` [PATCH v4 3/3] rtc-pcf2123: implement read_offset and set_offset Joshua Clayton 2016-02-05 20:41 ` [rtc-linux] " Joshua Clayton 2016-02-23 18:47 ` [PATCH v4 1/3] rtc: Add functions to set and read rtc offset Joshua Clayton 2016-02-23 18:47 ` [rtc-linux] " Joshua Clayton 2016-02-23 21:44 ` Alexandre Belloni 2016-02-23 21:44 ` [rtc-linux] " Alexandre Belloni 2016-02-03 17:16 ` [PATCH v3 2/3] rtc: implement a sysfs interface for clock offset Joshua Clayton 2016-02-03 17:16 ` [rtc-linux] " Joshua Clayton 2016-02-04 22:12 ` Alexandre Belloni 2016-02-04 22:12 ` [rtc-linux] " Alexandre Belloni 2016-02-03 17:16 ` Joshua Clayton [this message] 2016-02-03 17:16 ` [rtc-linux] [PATCH v3 3/3] rtc-pcf2123: implement read_offset and set_offset Joshua Clayton 2016-01-04 18:31 ` [PATCH v2 8/8] " Joshua Clayton 2016-01-04 18:31 ` [rtc-linux] " Joshua Clayton 2016-01-29 18:21 ` [PATCH v6 1/8] eal: pci: add api to rd/wr pci bar region Santosh Shukla 2016-01-29 18:21 ` [PATCH v6 2/8] linuxapp/vfio: ignore mapping for ioport region Santosh Shukla 2016-01-29 18:21 ` [PATCH v6 3/8] eal/linux: never check iopl for arm Santosh Shukla 2016-01-29 18:21 ` [PATCH v6 4/8] virtio: Introduce config RTE_VIRTIO_INC_VECTOR Santosh Shukla 2016-01-29 18:21 ` [PATCH v6 5/8] virtio: move io header and api from virtio_pci.h Santosh Shukla 2016-01-29 18:21 ` [PATCH v6 6/8] virtio: add vfio api to rd/wr ioport space Santosh Shukla 2016-02-01 12:48 ` Yuanhan Liu 2016-02-02 4:30 ` Santosh Shukla 2016-02-02 5:19 ` Yuanhan Liu 2016-02-02 6:02 ` Santosh Shukla 2016-01-29 18:21 ` [PATCH v6 7/8] virtio: extend pci rw api for vfio Santosh Shukla 2016-01-29 18:21 ` [PATCH v6 8/8] virtio: do not parse if interface is vfio Santosh Shukla 2016-02-01 13:48 ` [PATCH v6 1/8] eal: pci: add api to rd/wr pci bar region Yuanhan Liu 2016-02-02 4:14 ` Santosh Shukla 2016-02-02 5:43 ` Yuanhan Liu 2016-02-02 5:50 ` David Marchand 2016-02-02 8:49 ` Yuanhan Liu 2016-02-02 15:51 ` Santosh Shukla 2016-02-02 16:18 ` Santosh Shukla 2016-02-03 9:50 ` Santosh Shukla 2016-02-03 11:50 ` Yuanhan Liu 2016-02-05 17:56 ` David Marchand 2016-02-03 11:43 ` Yuanhan Liu 2016-02-02 7:00 ` Santosh Shukla 2016-02-02 7:01 ` Santosh Shukla 2016-02-08 10:03 ` [PATCH v8 3/4] eal/linux: vfio: ignore mapping for ioport region Santosh Shukla 2016-02-08 10:03 ` [PATCH v8 4/4] eal/linux: vfio: add pci ioport support Santosh Shukla 2016-02-08 14:13 ` Burakov, Anatoly 2016-02-09 9:04 ` David Marchand 2016-02-18 5:25 ` Santosh Shukla 2016-02-18 14:00 ` Thomas Monjalon 2016-01-26 14:56 ` [PATCH v2 0/8] rtc: enable adjustment of clock offset Joshua Clayton 2016-01-26 14:56 ` [rtc-linux] " Joshua Clayton 2016-01-26 16:00 ` Alexandre Belloni 2016-01-26 16:00 ` [rtc-linux] " Alexandre Belloni 2016-01-31 11:29 ` Alexandre Belloni 2016-01-31 11:29 ` [rtc-linux] " Alexandre Belloni
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