Patch "rtc: m41t80: fix SQW dividers override when setting a date" has been added to the 4.9-stable tree

Patch "rtc: m41t80: fix SQW dividers override when setting a date" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    rtc: m41t80: fix SQW dividers override when setting a date

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     rtc-m41t80-fix-sqw-dividers-override-when-setting-a-date.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Mon Apr  9 17:09:24 CEST 2018
From: Gary Bisson <gary.bisson@boundarydevices.com>
Date: Tue, 25 Apr 2017 16:45:15 +0200
Subject: rtc: m41t80: fix SQW dividers override when setting a date

From: Gary Bisson <gary.bisson@boundarydevices.com>


[ Upstream commit 0f546b058b86ea2f661cc7a6e931cee5a29959ef ]

This patch is only relevant for RTC with the SQ_ALT feature which
means the clock output frequency divider is stored in the weekday
register.

Current implementation discards the previous dividers value and clear
them as soon as the time is set.

Signed-off-by: Gary Bisson <gary.bisson@boundarydevices.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/rtc/rtc-m41t80.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- a/drivers/rtc/rtc-m41t80.c
+++ b/drivers/rtc/rtc-m41t80.c
@@ -168,6 +168,7 @@ static int m41t80_get_datetime(struct i2
 /* Sets the given date and time to the real time clock. */
 static int m41t80_set_datetime(struct i2c_client *client, struct rtc_time *tm)
 {
+	struct m41t80_data *clientdata = i2c_get_clientdata(client);
 	unsigned char buf[8];
 	int err, flags;
 
@@ -183,6 +184,17 @@ static int m41t80_set_datetime(struct i2
 	buf[M41T80_REG_YEAR] = bin2bcd(tm->tm_year - 100);
 	buf[M41T80_REG_WDAY] = tm->tm_wday;
 
+	/* If the square wave output is controlled in the weekday register */
+	if (clientdata->features & M41T80_FEATURE_SQ_ALT) {
+		int val;
+
+		val = i2c_smbus_read_byte_data(client, M41T80_REG_WDAY);
+		if (val < 0)
+			return val;
+
+		buf[M41T80_REG_WDAY] |= (val & 0xf0);
+	}
+
 	err = i2c_smbus_write_i2c_block_data(client, M41T80_REG_SSEC,
 					     sizeof(buf), buf);
 	if (err < 0) {


Patches currently in stable-queue which might be from gary.bisson@boundarydevices.com are

queue-4.9/rtc-m41t80-fix-sqw-dividers-override-when-setting-a-date.patch