linux-kernel - Re: [PATCH] watchdog: max63xx_wdt: Add support for specifying WDI logic via GPIO

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Date:   Thu, 28 Apr 2022 06:10:56 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Pali Rohár <pali@...nel.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Rob Herring <robh+dt@...nel.org>
Cc:     linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] watchdog: max63xx_wdt: Add support for specifying WDI
 logic via GPIO

On 4/28/22 02:16, Pali Rohár wrote:
> 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@...nel.org>

How is that different to just using the gpio watchdog driver ?

Guenter

> ---
>   .../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;