openwrt/target/linux/brcm2708/patches-4.14/950-0436-Revert-rtc-pcf8523-properly-handle-oscillator-stop-b.patch

From e37bc7714591ac7a94200ee254a116904e19b784 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.org>
Date: Mon, 29 Oct 2018 14:45:45 +0000
Subject: [PATCH 436/454] 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>
---
 drivers/rtc/rtc-pcf8523.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

--- a/drivers/rtc/rtc-pcf8523.c
+++ b/drivers/rtc/rtc-pcf8523.c
@@ -209,8 +209,28 @@ static int pcf8523_rtc_read_time(struct
 	if (err < 0)
 		return err;
 
-	if (regs[0] & REG_SECONDS_OS)
-		return -EINVAL;
+	if (regs[0] & REG_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] &= ~REG_SECONDS_OS;
+
+		err = pcf8523_write(client, REG_SECONDS, regs[0]);
+		if (err < 0)
+			return err;
+
+		err = pcf8523_read(client, REG_SECONDS, &regs[0]);
+		if (err < 0)
+			return err;
+
+		if (regs[0] & REG_SECONDS_OS)
+			return -EAGAIN;
+	}
 
 	tm->tm_sec = bcd2bin(regs[0] & 0x7f);
 	tm->tm_min = bcd2bin(regs[1] & 0x7f);
@@ -246,7 +266,6 @@ static int pcf8523_rtc_set_time(struct d
 		return err;
 
 	regs[0] = REG_SECONDS;
-	/* This will purposely overwrite REG_SECONDS_OS */
 	regs[1] = bin2bcd(tm->tm_sec);
 	regs[2] = bin2bcd(tm->tm_min);
 	regs[3] = bin2bcd(tm->tm_hour);