watchdog: pm8916_wdt: Report reboot reason

The PM8916 PMIC provides "power-off reason" (POFF_REASON) registers
to allow detecting why the board was powered off or rebooted. This
can be used to expose if a reset happened due to a watchdog timeout.
The watchdog API also provides status bits for overtemperature and
undervoltage which happen to be reported in the same PMIC register.

Make this information available as part of the watchdog device
so userspace can decide to handle the situation accordingly.

Signed-off-by: Stephan Gerhold <stephan.gerhold@kernkonzept.com>
Reviewed-by: Loic Poulain <loic.poulain@linaro.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20220629084816.125515-3-stephan.gerhold@kernkonzept.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/pm8916_wdt.c

@@ -9,6 +9,12 @@
 #include <linux/regmap.h>
 #include <linux/watchdog.h>
 
+#define PON_POFF_REASON1		0x0c
+#define PON_POFF_REASON1_PMIC_WD	BIT(2)
+#define PON_POFF_REASON2		0x0d
+#define PON_POFF_REASON2_UVLO		BIT(5)
+#define PON_POFF_REASON2_OTST3		BIT(6)
+
 #define PON_INT_RT_STS			0x10
 #define PMIC_WD_BARK_STS_BIT		BIT(6)
 
@@ -110,12 +116,14 @@ static irqreturn_t pm8916_wdt_isr(int irq, void *arg)
 }
 
 static const struct watchdog_info pm8916_wdt_ident = {
-	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
+	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE |
+		   WDIOF_OVERHEAT | WDIOF_CARDRESET | WDIOF_POWERUNDER,
 	.identity = "QCOM PM8916 PON WDT",
 };
 
 static const struct watchdog_info pm8916_wdt_pt_ident = {
 	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE |
+		   WDIOF_OVERHEAT | WDIOF_CARDRESET | WDIOF_POWERUNDER |
 		   WDIOF_PRETIMEOUT,
 	.identity = "QCOM PM8916 PON WDT",
 };
@@ -135,6 +143,7 @@ static int pm8916_wdt_probe(struct platform_device *pdev)
 	struct pm8916_wdt *wdt;
 	struct device *parent;
 	int err, irq;
+	u8 poff[2];
 
 	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
 	if (!wdt)
@@ -175,6 +184,21 @@ static int pm8916_wdt_probe(struct platform_device *pdev)
 		wdt->wdev.info = &pm8916_wdt_ident;
 	}
 
+	err = regmap_bulk_read(wdt->regmap, wdt->baseaddr + PON_POFF_REASON1,
+			       &poff, ARRAY_SIZE(poff));
+	if (err) {
+		dev_err(dev, "failed to read POFF reason: %d\n", err);
+		return err;
+	}
+
+	dev_dbg(dev, "POFF reason: %#x %#x\n", poff[0], poff[1]);
+	if (poff[0] & PON_POFF_REASON1_PMIC_WD)
+		wdt->wdev.bootstatus |= WDIOF_CARDRESET;
+	if (poff[1] & PON_POFF_REASON2_UVLO)
+		wdt->wdev.bootstatus |= WDIOF_POWERUNDER;
+	if (poff[1] & PON_POFF_REASON2_OTST3)
+		wdt->wdev.bootstatus |= WDIOF_OVERHEAT;
+
 	/* Configure watchdog to hard-reset mode */
 	err = regmap_write(wdt->regmap,
 			   wdt->baseaddr + PON_PMIC_WD_RESET_S2_CTL,