watchdog: rn5t618: add support for read out bootstatus

The PMIC does store the power-off factor internally.
Read it out and report it as bootstatus.

Signed-off-by: Marcus Folkesson <[e-mail]>
Acked-by: Lee Jones <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Guenter Roeck <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

drivers/watchdog/rn5t618_wdt.c

···
 	struct rn5t618 *rn5t618 = dev_get_drvdata(dev->parent);
 	struct rn5t618_wdt *wdt;
 	int min_timeout, max_timeout;
+	int ret;
+	unsigned int val;
 
 	wdt = devm_kzalloc(dev, sizeof(struct rn5t618_wdt), GFP_KERNEL);
 	if (!wdt)
···
 	wdt->wdt_dev.max_timeout = max_timeout;
 	wdt->wdt_dev.timeout = max_timeout;
 	wdt->wdt_dev.parent = dev;
+
+	/* Read out previous power-off factor */
+	ret = regmap_read(wdt->rn5t618->regmap, RN5T618_POFFHIS, &val);
+	if (ret)
+		return ret;
+
+	if (val & RN5T618_POFFHIS_VINDET)
+		wdt->wdt_dev.bootstatus = WDIOF_POWERUNDER;
+	else if (val & RN5T618_POFFHIS_WDG)
+		wdt->wdt_dev.bootstatus = WDIOF_CARDRESET;
 
 	watchdog_set_drvdata(&wdt->wdt_dev, wdt);
 	watchdog_init_timeout(&wdt->wdt_dev, timeout, dev);

include/linux/mfd/rn5t618.h

···
 #define RN5T618_WATCHDOG_WDOGTIM_S	0
 #define RN5T618_PWRIRQ_IR_WDOG		BIT(6)
 
+#define RN5T618_POFFHIS_PWRON		BIT(0)
+#define RN5T618_POFFHIS_TSHUT		BIT(1)
+#define RN5T618_POFFHIS_VINDET		BIT(2)
+#define RN5T618_POFFHIS_IODET		BIT(3)
+#define RN5T618_POFFHIS_CPU		BIT(4)
+#define RN5T618_POFFHIS_WDG		BIT(5)
+#define RN5T618_POFFHIS_DCLIM		BIT(6)
+#define RN5T618_POFFHIS_N_OE		BIT(7)
+
 enum {
 	RN5T618_DCDC1,
 	RN5T618_DCDC2,