rtc: pcf2127: Run a OTP refresh if not done before

The datasheet of the PCF2127 states, it is recommended to process an OTP
refresh once the power is up and the oscillator is operating stable. The
OTP refresh takes less than 100 ms to complete.
Signed-off-by: Philipp Rosenberger <p.rosenberger@kunbus.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210118085752.5759-3-p.rosenberger@kunbus.com

drivers/rtc/rtc-pcf2127.c

@@ -58,6 +58,9 @@
 #define PCF2127_REG_ALARM_DM		0x0D
 #define PCF2127_REG_ALARM_DW		0x0E
 #define PCF2127_BIT_ALARM_AE			BIT(7)
+/* CLKOUT control register */
+#define PCF2127_REG_CLKOUT		0x0f
+#define PCF2127_BIT_CLKOUT_OTPR			BIT(5)
 /* Watchdog registers */
 #define PCF2127_REG_WD_CTL		0x10
 #define PCF2127_BIT_WD_CTL_TF0			BIT(0)
@@ -559,6 +562,7 @@ static int pcf2127_probe(struct device *dev, struct regmap *regmap,
 {
 	struct pcf2127 *pcf2127;
 	int ret = 0;
+	unsigned int val;
 
 	dev_dbg(dev, "%s\n", __func__);
 
@@ -615,6 +619,19 @@ static int pcf2127_probe(struct device *dev, struct regmap *regmap,
 	regmap_clear_bits(pcf2127->regmap, PCF2127_REG_CTRL1,
 				PCF2127_BIT_CTRL1_POR_OVRD);
 
+	ret = regmap_read(pcf2127->regmap, PCF2127_REG_CLKOUT, &val);
+	if (ret < 0)
+		return ret;
+
+	if (!(val & PCF2127_BIT_CLKOUT_OTPR)) {
+		ret = regmap_set_bits(pcf2127->regmap, PCF2127_REG_CLKOUT,
+				      PCF2127_BIT_CLKOUT_OTPR);
+		if (ret < 0)
+			return ret;
+
+		msleep(100);
+	}
+
 	/*
 	 * Watchdog timer enabled and reset pin /RST activated when timed out.
 	 * Select 1Hz clock source for watchdog timer.