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: Vesa Jääskeläinen <vesa.jaaskelainen@vaisala.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
diff --git a/drivers/rtc/rtc-tps65910.c b/drivers/rtc/rtc-tps65910.c
index 5a3d53c..9dd1db9a 100644
--- a/drivers/rtc/rtc-tps65910.c
+++ b/drivers/rtc/rtc-tps65910.c
@@ -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)
