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rtc: tps65910: Add RTC calibration support

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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: Vesa Jääskeläinen <vesa.jaaskelainen@vaisala.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
This commit is contained in:
Vesa Jääskeläinen 2016-12-23 13:15:58 +02:00 committed by Alexandre Belloni
parent 666b5d1e9f
commit aecb57da7a
2 changed files with 144 additions and 0 deletions
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143
drivers/rtc/rtc-tps65910.c
View File

@ -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)

1
include/linux/mfd/tps65910.h
View File

@ -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 */