queue-6.1/rtc-ds1307-remove-clear-of-oscillator-stop-flag-osf-.patch

From 1845089501dc777ff1d3ea392e1216985a31bf43 Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Wed, 11 Jun 2025 11:14:15 -0700
Subject: rtc: ds1307: remove clear of oscillator stop flag (OSF) in probe

From: Meagan Lloyd <meaganlloyd@linux.microsoft.com>

[ Upstream commit 48458654659c9c2e149c211d86637f1592470da5 ]

In using CONFIG_RTC_HCTOSYS, rtc_hctosys() will sync the RTC time to the
kernel time as long as rtc_read_time() succeeds. In some power loss
situations, our supercapacitor-backed DS1342 RTC comes up with either an
unpredictable future time or the default 01/01/00 from the datasheet.
The oscillator stop flag (OSF) is set in these scenarios due to the
power loss and can be used to determine the validity of the RTC data.

Some chip types in the ds1307 driver already have OSF handling to
determine whether .read_time provides valid RTC data or returns -EINVAL.

This change removes the clear of the OSF in .probe as the OSF needs to
be preserved to expand the OSF handling to the ds1341 chip type (note
that DS1341 and DS1342 share a datasheet).

Signed-off-by: Meagan Lloyd <meaganlloyd@linux.microsoft.com>
Reviewed-by: Tyler Hicks <code@tyhicks.com>
Acked-by: Rodolfo Giometti <giometti@enneenne.com>
Link: https://lore.kernel.org/r/1749665656-30108-2-git-send-email-meaganlloyd@linux.microsoft.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/rtc/rtc-ds1307.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 530b9340db21..6d82fb45e9a8 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -1819,10 +1819,8 @@ static int ds1307_probe(struct i2c_client *client,
 		regmap_write(ds1307->regmap, DS1337_REG_CONTROL,
 			     regs[0]);
 
-		/* oscillator fault?  clear flag, and warn */
+		/* oscillator fault? warn */
 		if (regs[1] & DS1337_BIT_OSF) {
-			regmap_write(ds1307->regmap, DS1337_REG_STATUS,
-				     regs[1] & ~DS1337_BIT_OSF);
 			dev_warn(ds1307->dev, "SET TIME!\n");
 		}
 		break;
-- 
2.39.5