rtc: ds3232/ds3231: Add support to generate 32KHz output for driver module

Add an implementation of the rtc_enable_32khz_output() that uses the
driver model i2c APIs.

Also put code related to rtc_enable_32khz_output
under CONFIG_RTC_ENABLE_32KHZ_OUTPUT.

Signed-off-by: Chuanhua Han <chuanhua.han@nxp.com>
Reviewed-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 860b73d..8778cc7 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -31,6 +31,12 @@
 	  drivers to perform the actual functions. See rtc.h for a
 	  description of the API.
 
+config RTC_ENABLE_32KHZ_OUTPUT
+	bool "Enable RTC 32Khz output"
+	help
+	   Some real-time clocks support the output of 32kHz square waves (such as ds3231),
+	   the config symbol choose Real Time Clock device 32Khz output feature.
+
 config RTC_PCF2127
 	bool "Enable PCF2127 driver"
 	depends on DM_RTC
diff --git a/drivers/rtc/ds3231.c b/drivers/rtc/ds3231.c
index 79b026a..fde4d86 100644
--- a/drivers/rtc/ds3231.c
+++ b/drivers/rtc/ds3231.c
@@ -148,11 +148,13 @@
 /*
  * Enable 32KHz output
  */
+#ifdef CONFIG_RTC_ENABLE_32KHZ_OUTPUT
 void rtc_enable_32khz_output(void)
 {
 	rtc_write(RTC_STAT_REG_ADDR,
 		  RTC_STAT_BIT_BB32KHZ | RTC_STAT_BIT_EN32KHZ);
 }
+#endif
 
 /*
  * Helper functions
@@ -251,6 +253,21 @@
 	return 0;
 }
 
+#ifdef CONFIG_RTC_ENABLE_32KHZ_OUTPUT
+int rtc_enable_32khz_output(int busnum, int chip_addr)
+{
+	int ret;
+	struct udevice *dev;
+
+	ret = i2c_get_chip_for_busnum(busnum, chip_addr, 1, &dev);
+	if (!ret)
+		ret = dm_i2c_reg_write(dev, RTC_STAT_REG_ADDR,
+				       RTC_STAT_BIT_BB32KHZ |
+				       RTC_STAT_BIT_EN32KHZ);
+	return ret;
+}
+#endif
+
 static const struct rtc_ops ds3231_rtc_ops = {
 	.get = ds3231_rtc_get,
 	.set = ds3231_rtc_set,