linux-kernel - [PATCH] rtc: ds1307: provide an indication that the watchdog has fired

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Date:   Fri, 24 Jul 2020 16:50:09 +1200
From:   Chris Packham <chris.packham@...iedtelesis.co.nz>
To:     a.zummo@...ertech.it, alexandre.belloni@...tlin.com
Cc:     linux-rtc@...r.kernel.org, linux-watchdog@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Chris Packham <chris.packham@...iedtelesis.co.nz>
Subject: [PATCH] rtc: ds1307: provide an indication that the watchdog has fired

There's not much feedback when the ds1388 watchdog fires. Generally it
yanks on the reset line and the board reboots. To provide some feedback
indicate that the watchdog has fired in the past. This should help
distinguish a watchdog triggered reset from a power interruption.

Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
---
 drivers/rtc/rtc-ds1307.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 49702942bb08..431b1a50c483 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -868,6 +868,14 @@ static int ds1388_wdt_start(struct watchdog_device *wdt_dev)
 	struct ds1307 *ds1307 = watchdog_get_drvdata(wdt_dev);
 	u8 regs[2];
 	int ret;
+	int val;
+
+	ret = regmap_read(ds1307->regmap, DS1388_REG_FLAG, &val);
+	if (ret)
+		return ret;
+
+	if (val & DS1388_BIT_WF)
+		dev_notice(ds1307->dev, "detected watchdog alarm flag\n");
 
 	ret = regmap_update_bits(ds1307->regmap, DS1388_REG_FLAG,
 				 DS1388_BIT_WF, 0);
-- 
2.27.0