linux-kernel - [PATCH] rtc: pcf8523: fix for stop bit

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Message-ID: <20220829124639.10906-1-paulmn@axis.com>
Date:   Mon, 29 Aug 2022 14:46:39 +0200
From:   paulmn <paulmn@...s.com>
To:     <alexandre.belloni@...tlin.com>
CC:     paulmn <paulmn@...s.com>, Alessandro Zummo <a.zummo@...ertech.it>,
        <linux-rtc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] rtc: pcf8523: fix for stop bit

Bugfix for an issue detected when a goldcap capacitor gets
fully discharged due to a long absence of the power supply,
and then recharges again. The RTC failed to continue to keep
the real-time clock.

This was caused by the incorrect handling of the STOP bit in
the RTC internal register.  This fix solves the problem.

Signed-off-by: paulmn <paulmn@...s.com>
---
 drivers/rtc/rtc-pcf8523.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/rtc/rtc-pcf8523.c b/drivers/rtc/rtc-pcf8523.c
index 6174b3fd4b98..92de99f11a7a 100644
--- a/drivers/rtc/rtc-pcf8523.c
+++ b/drivers/rtc/rtc-pcf8523.c
@@ -99,24 +99,24 @@ static irqreturn_t pcf8523_irq(int irq, void *dev_id)
 static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
 	struct pcf8523 *pcf8523 = dev_get_drvdata(dev);
-	u8 regs[7];
+	u8 regs[10];
 	int err;
 
-	err = regmap_bulk_read(pcf8523->regmap, PCF8523_REG_SECONDS, regs,
+	err = regmap_bulk_read(pcf8523->regmap, PCF8523_REG_CONTROL1, regs,
 			       sizeof(regs));
 	if (err < 0)
 		return err;
 
-	if (regs[0] & PCF8523_SECONDS_OS)
+	if ((regs[0] & PCF8523_CONTROL1_STOP) || (regs[3] & PCF8523_SECONDS_OS))
 		return -EINVAL;
 
-	tm->tm_sec = bcd2bin(regs[0] & 0x7f);
-	tm->tm_min = bcd2bin(regs[1] & 0x7f);
-	tm->tm_hour = bcd2bin(regs[2] & 0x3f);
-	tm->tm_mday = bcd2bin(regs[3] & 0x3f);
-	tm->tm_wday = regs[4] & 0x7;
-	tm->tm_mon = bcd2bin(regs[5] & 0x1f) - 1;
-	tm->tm_year = bcd2bin(regs[6]) + 100;
+	tm->tm_sec = bcd2bin(regs[3] & 0x7f);
+	tm->tm_min = bcd2bin(regs[4] & 0x7f);
+	tm->tm_hour = bcd2bin(regs[5] & 0x3f);
+	tm->tm_mday = bcd2bin(regs[6] & 0x3f);
+	tm->tm_wday = regs[7] & 0x7;
+	tm->tm_mon = bcd2bin(regs[8] & 0x1f) - 1;
+	tm->tm_year = bcd2bin(regs[9]) + 100;
 
 	return 0;
 }
-- 
2.30.2