From: Phil Elwell <phil@raspberrypi.org>
Date: Mon, 29 Oct 2018 14:45:45 +0000 (+0000)
Subject: Revert "rtc: pcf8523: properly handle oscillator stop bit"
X-Git-Tag: accepted/tizen/unified/20230118.172025~1546
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=81196883119c287701f17d4465e48b6fea960fd6;p=platform%2Fkernel%2Flinux-rpi.git

Revert "rtc: pcf8523: properly handle oscillator stop bit"

This reverts commit ede44c908d44b166a5b6bd7caacd105c2ff5a70f.

See: https://github.com/raspberrypi/firmware/issues/1065

Signed-off-by: Phil Elwell <phil@raspberrypi.org>
---

diff --git a/drivers/rtc/rtc-pcf8523.c b/drivers/rtc/rtc-pcf8523.c
index 8b6fb20..ad2231f 100644
--- a/drivers/rtc/rtc-pcf8523.c
+++ b/drivers/rtc/rtc-pcf8523.c
@@ -242,8 +242,28 @@ static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm)
 	if (err < 0)
 		return err;
 
-	if (regs[0] & PCF8523_SECONDS_OS)
-		return -EINVAL;
+	if (regs[0] & PCF8523_SECONDS_OS) {
+		/*
+		 * If the oscillator was stopped, try to clear the flag. Upon
+		 * power-up the flag is always set, but if we cannot clear it
+		 * the oscillator isn't running properly for some reason. The
+		 * sensible thing therefore is to return an error, signalling
+		 * that the clock cannot be assumed to be correct.
+		 */
+
+		regs[0] &= ~PCF8523_SECONDS_OS;
+
+		err = pcf8523_write(client, PCF8523_REG_SECONDS, regs[0]);
+		if (err < 0)
+			return err;
+
+		err = pcf8523_read(client, PCF8523_REG_SECONDS, &regs[0]);
+		if (err < 0)
+			return err;
+
+		if (regs[0] & PCF8523_SECONDS_OS)
+			return -EAGAIN;
+	}
 
 	tm->tm_sec = bcd2bin(regs[0] & 0x7f);
 	tm->tm_min = bcd2bin(regs[1] & 0x7f);