[rtc-linux] [PATCH 2/2] rtc: ds1307: disable square wave output from ds1308

[Sean Nyekjaer <sean.nyekjaer@prevas.dk>]

Disable sqw output from ds1308 in order to reduce
the power consumption by ~50%.

Signed-off-by: Sean Nyekjaer <sean.nyekjaer@prevas.dk>
---
 drivers/rtc/rtc-ds1307.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index a4ef03ad9395..8d9f25a3c757 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -78,6 +78,7 @@ enum ds_type {
 #	define DS1307_BIT_OUT		0x80
 #	define DS1338_BIT_OSF		0x20
 #	define DS1307_BIT_SQWE		0x10
+#	define DS1308_BIT_BBCLK		0x04
 #	define DS1307_BIT_RS1		0x02
 #	define DS1307_BIT_RS0		0x01
 #define DS1337_REG_CONTROL	0x0e
@@ -1454,6 +1455,11 @@ static int ds1307_probe(struct i2c_client *client,
 		}
 		break;
 	case ds_1308:
+		/* disable sqw when driven from battery backup */
+		if (ds1307->regs[DS1307_REG_CONTROL] & DS1308_BIT_BBCLK)
+			i2c_smbus_write_byte_data(client, DS1307_REG_CONTROL,
+					ds1307->regs[DS1307_REG_CONTROL]
+					& ~DS1338_BIT_BBCLK);
 	case ds_1338:
 		/* clock halted?  turn it on, so clock can tick. */
 		if (tmp & DS1307_BIT_CH)
-- 
2.13.0

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