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

RTC devices can generate 32KHz output if for
-DS3232 device, EN32KHz bit and BB32KHz bit are set
-DS3231 device, EN32KHz bit is set, BB32KHz bit is don't care

Patch adds rtc_enable_32khz_output() which when called
will enable 32KHz output on 32KHz pin

Signed-off-by: Priyanka Jain <Priyanka.Jain@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>

drivers/rtc/ds3231.c

@@ -49,6 +49,8 @@
 #define RTC_STAT_BIT_A1F	0x1	/* Alarm 1 flag                 */
 #define RTC_STAT_BIT_A2F	0x2	/* Alarm 2 flag                 */
 #define RTC_STAT_BIT_OSF	0x80	/* Oscillator stop flag         */
+#define RTC_STAT_BIT_BB32KHZ	0x40	/* Battery backed 32KHz Output  */
+#define RTC_STAT_BIT_EN32KHZ	0x8	/* Enable 32KHz Output  */
 
 
 static uchar rtc_read (uchar reg);
@@ -141,6 +143,14 @@ void rtc_reset (void)
 	rtc_write (RTC_CTL_REG_ADDR, RTC_CTL_BIT_RS1 | RTC_CTL_BIT_RS2);
 }
 
+/*
+ * Enable 32KHz output
+ */
+void rtc_enable_32khz_output(void)
+{
+	rtc_write(RTC_STAT_REG_ADDR,
+		  RTC_STAT_BIT_BB32KHZ | RTC_STAT_BIT_EN32KHZ);
+}
 
 /*
  * Helper functions

include/rtc.h

@@ -151,6 +151,7 @@ int rtc_write32(struct udevice *dev, unsigned int reg, u32 value);
 int rtc_get (struct rtc_time *);
 int rtc_set (struct rtc_time *);
 void rtc_reset (void);
+void rtc_enable_32khz_output(void);
 
 /**
  * rtc_read8() - Read an 8-bit register