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Commit aecb57da authored by Vesa Jääskeläinen's avatar Vesa Jääskeläinen Committed by Alexandre Belloni
Browse files

rtc: tps65910: Add RTC calibration support 



Texas Instrument's TPS65910 has support for compensating RTC crystal
inaccuracies. When enabled every hour RTC counter value will be compensated
with two's complement value.

Signed-off-by: default avatarVesa Jääskeläinen <vesa.jaaskelainen@vaisala.com>
Acked-by: default avatarLee Jones <lee.jones@linaro.org>
Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@free-electrons.com>
parent 666b5d1e

drivers/rtc/rtc-tps65910.c

+143 −0
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <linux/types.h>

#include <linux/rtc.h>

#include <linux/bcd.h>

#include <linux/math64.h>

#include <linux/platform_device.h>

#include <linux/interrupt.h>

#include <linux/mfd/tps65910.h>
@@ -33,6 +34,19 @@ struct tps65910_rtc { 
/* Total number of RTC registers needed to set time*/

#define NUM_TIME_REGS	(TPS65910_YEARS - TPS65910_SECONDS + 1)



/* Total number of RTC registers needed to set compensation registers */

#define NUM_COMP_REGS	(TPS65910_RTC_COMP_MSB - TPS65910_RTC_COMP_LSB + 1)



/* Min and max values supported with 'offset' interface (swapped sign) */

#define MIN_OFFSET	(-277761)

#define MAX_OFFSET	(277778)



/* Number of ticks per hour */

#define TICKS_PER_HOUR	(32768 * 3600)



/* Multiplier for ppb conversions */

#define PPB_MULT	(1000000000LL)



static int tps65910_rtc_alarm_irq_enable(struct device *dev, unsigned enabled)

{

	struct tps65910 *tps = dev_get_drvdata(dev->parent);
@@ -187,6 +201,133 @@ static int tps65910_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm) 
	return ret;

}



static int tps65910_rtc_set_calibration(struct device *dev, int calibration)

{

	unsigned char comp_data[NUM_COMP_REGS];

	struct tps65910 *tps = dev_get_drvdata(dev->parent);

	s16 value;

	int ret;



	/*

	 * TPS65910 uses two's complement 16 bit value for compensation for RTC

	 * crystal inaccuracies. One time every hour when seconds counter

	 * increments from 0 to 1 compensation value will be added to internal

	 * RTC counter value.

	 *

	 * Compensation value 0x7FFF is prohibited value.

	 *

	 * Valid range for compensation value: [-32768 .. 32766]

	 */

	if ((calibration < -32768) || (calibration > 32766)) {

		dev_err(dev, "RTC calibration value out of range: %d\n",

			calibration);

		return -EINVAL;

	}



	value = (s16)calibration;



	comp_data[0] = (u16)value & 0xFF;

	comp_data[1] = ((u16)value >> 8) & 0xFF;



	/* Update all the compensation registers in one shot */

	ret = regmap_bulk_write(tps->regmap, TPS65910_RTC_COMP_LSB,

		comp_data, NUM_COMP_REGS);

	if (ret < 0) {

		dev_err(dev, "rtc_set_calibration error: %d\n", ret);

		return ret;

	}



	/* Enable automatic compensation */

	ret = regmap_update_bits(tps->regmap, TPS65910_RTC_CTRL,

		TPS65910_RTC_CTRL_AUTO_COMP, TPS65910_RTC_CTRL_AUTO_COMP);

	if (ret < 0)

		dev_err(dev, "auto_comp enable failed with error: %d\n", ret);



	return ret;

}



static int tps65910_rtc_get_calibration(struct device *dev, int *calibration)

{

	unsigned char comp_data[NUM_COMP_REGS];

	struct tps65910 *tps = dev_get_drvdata(dev->parent);

	unsigned int ctrl;

	u16 value;

	int ret;



	ret = regmap_read(tps->regmap, TPS65910_RTC_CTRL, &ctrl);

	if (ret < 0)

		return ret;



	/* If automatic compensation is not enabled report back zero */

	if (!(ctrl & TPS65910_RTC_CTRL_AUTO_COMP)) {

		*calibration = 0;

		return 0;

	}



	ret = regmap_bulk_read(tps->regmap, TPS65910_RTC_COMP_LSB, comp_data,

		NUM_COMP_REGS);

	if (ret < 0) {

		dev_err(dev, "rtc_get_calibration error: %d\n", ret);

		return ret;

	}



	value = (u16)comp_data[0] | ((u16)comp_data[1] << 8);



	*calibration = (s16)value;



	return 0;

}



static int tps65910_read_offset(struct device *dev, long *offset)

{

	int calibration;

	s64 tmp;

	int ret;



	ret = tps65910_rtc_get_calibration(dev, &calibration);

	if (ret < 0)

		return ret;



	/* Convert from RTC calibration register format to ppb format */

	tmp = calibration * (s64)PPB_MULT;

	if (tmp < 0)

		tmp -= TICKS_PER_HOUR / 2LL;

	else

		tmp += TICKS_PER_HOUR / 2LL;

	tmp = div_s64(tmp, TICKS_PER_HOUR);



	/* Offset value operates in negative way, so swap sign */

	*offset = (long)-tmp;



	return 0;

}



static int tps65910_set_offset(struct device *dev, long offset)

{

	int calibration;

	s64 tmp;

	int ret;



	/* Make sure offset value is within supported range */

	if (offset < MIN_OFFSET || offset > MAX_OFFSET)

		return -ERANGE;



	/* Convert from ppb format to RTC calibration register format */

	tmp = offset * (s64)TICKS_PER_HOUR;

	if (tmp < 0)

		tmp -= PPB_MULT / 2LL;

	else

		tmp += PPB_MULT / 2LL;

	tmp = div_s64(tmp, PPB_MULT);



	/* Offset value operates in negative way, so swap sign */

	calibration = (int)-tmp;



	ret = tps65910_rtc_set_calibration(dev, calibration);



	return ret;

}



static irqreturn_t tps65910_rtc_interrupt(int irq, void *rtc)

{

	struct device *dev = rtc;
@@ -219,6 +360,8 @@ static const struct rtc_class_ops tps65910_rtc_ops = { 
	.read_alarm	= tps65910_rtc_read_alarm,

	.set_alarm	= tps65910_rtc_set_alarm,

	.alarm_irq_enable = tps65910_rtc_alarm_irq_enable,

	.read_offset	= tps65910_read_offset,

	.set_offset	= tps65910_set_offset,

};



static int tps65910_rtc_probe(struct platform_device *pdev)

include/linux/mfd/tps65910.h

+1 −0
Original line number Diff line number Diff line
@@ -134,6 +134,7 @@ 


/* RTC_CTRL_REG bitfields */

#define TPS65910_RTC_CTRL_STOP_RTC			0x01 /*0=stop, 1=run */

#define TPS65910_RTC_CTRL_AUTO_COMP			0x04

#define TPS65910_RTC_CTRL_GET_TIME			0x40



/* RTC_STATUS_REG bitfields */