[PATCH] watchdog: max63xx_wdt: Add support for specifying WDI logic via GPIO

[Pali Rohár <pali@xxxxxxxxxx>]

On some boards is WDI logic of max6370 chip connected via GPIO. So extend
max63xx_wdt driver and DTS schema to allow specifying WDI logic via GPIO.

Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>
---
 .../bindings/watchdog/maxim,max63xx.yaml      |  4 +++
 drivers/watchdog/max63xx_wdt.c                | 28 +++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/Documentation/devicetree/bindings/watchdog/maxim,max63xx.yaml b/Documentation/devicetree/bindings/watchdog/maxim,max63xx.yaml
index ab9641e845db..a97aa0135ef9 100644
--- a/Documentation/devicetree/bindings/watchdog/maxim,max63xx.yaml
+++ b/Documentation/devicetree/bindings/watchdog/maxim,max63xx.yaml
@@ -27,6 +27,10 @@ properties:
     description: This is a 1-byte memory-mapped address
     maxItems: 1
 
+  gpios:
+    description: Optional GPIO used for controlling WDI when WDI bit is not mapped to memory
+    maxItems: 1
+
 required:
   - compatible
   - reg
diff --git a/drivers/watchdog/max63xx_wdt.c b/drivers/watchdog/max63xx_wdt.c
index 9e1541cfae0d..eaf00c3f06a5 100644
--- a/drivers/watchdog/max63xx_wdt.c
+++ b/drivers/watchdog/max63xx_wdt.c
@@ -27,6 +27,7 @@
 #include <linux/io.h>
 #include <linux/slab.h>
 #include <linux/property.h>
+#include <linux/gpio/consumer.h>
 
 #define DEFAULT_HEARTBEAT 60
 #define MAX_HEARTBEAT     60
@@ -53,6 +54,9 @@ struct max63xx_wdt {
 	void __iomem *base;
 	spinlock_t lock;
 
+	/* GPIOs */
+	struct gpio_desc *gpio_wdi;
+
 	/* WDI and WSET bits write access routines */
 	void (*ping)(struct max63xx_wdt *wdt);
 	void (*set)(struct max63xx_wdt *wdt, u8 set);
@@ -158,6 +162,17 @@ static const struct watchdog_info max63xx_wdt_info = {
 	.identity = "max63xx Watchdog",
 };
 
+static void max63xx_gpio_ping(struct max63xx_wdt *wdt)
+{
+	spin_lock(&wdt->lock);
+
+	gpiod_set_value_cansleep(wdt->gpio_wdi, 1);
+	udelay(1);
+	gpiod_set_value_cansleep(wdt->gpio_wdi, 0);
+
+	spin_unlock(&wdt->lock);
+}
+
 static void max63xx_mmap_ping(struct max63xx_wdt *wdt)
 {
 	u8 val;
@@ -225,6 +240,19 @@ static int max63xx_wdt_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
+	wdt->gpio_wdi = devm_gpiod_get(dev, NULL, GPIOD_FLAGS_BIT_DIR_OUT);
+	if (IS_ERR(wdt->gpio_wdi) && PTR_ERR(wdt->gpio_wdi) != -ENOENT) {
+		if (PTR_ERR(wdt->gpio_wdi) != -EPROBE_DEFER)
+			dev_err(dev, "unable to request gpio: %ld\n",
+				PTR_ERR(wdt->gpio_wdi));
+		return PTR_ERR(wdt->gpio_wdi);
+	}
+
+	if (!IS_ERR(wdt->gpio_wdi))
+		wdt->ping = max63xx_gpio_ping;
+	else
+		wdt->gpio_wdi = NULL;
+
 	err = max63xx_mmap_init(pdev, wdt);
 	if (err)
 		return err;
-- 
2.20.1