[PATCH] watchdog: gpio_wdt: add support for stoppable devices

[Stefan Roese]

On 10/2/24 21:23, Rasmus Villemoes wrote:
> Back when I added this driver in commit 2ac8490412c9, I wrote
> 
>      The corresponding linux driver apparently has support for some
>      watchdog circuits which can be disabled by tri-stating the gpio, but I
>      have never actually encountered such a chip in the wild;
> 
> That has changed now; I have a board with just such a watchdog on my
> desk currently. Add support for that.
> 
> - For a hw_algo="toggle" device, the gpio is requested as output if the
>    always-running flag is set, otherwise as input.
> 
> - The ->start() method is updated to change the direction to output when
>    required (i.e. it is not always-running).
> 
> - The ->stop() method is implemented, but of course reports failure if
>    always-running.
> 
> As I still haven't met any hw_algo="level" devices, I'm not entirely
> sure how they fit in, but I'm borrowing logic from the corresponding
> linux driver:
> 
> - In ->probe(), such devices always request the gpio as GPIOD_IS_OUT.
> 
> - In ->stop(), the linux driver has an "eternal ping" comment and sets
>    the gpio to (logic) high.
> 
> Signed-off-by: Rasmus Villemoes <ravi at prevas.dk>

Reviewed-by: Stefan Roese <sr at denx.de>

Thanks,
Stefan

> ---
>   drivers/watchdog/gpio_wdt.c | 27 ++++++++++++++++++++++++---
>   1 file changed, 24 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/watchdog/gpio_wdt.c b/drivers/watchdog/gpio_wdt.c
> index 2920c2c751f..e889861e917 100644
> --- a/drivers/watchdog/gpio_wdt.c
> +++ b/drivers/watchdog/gpio_wdt.c
> @@ -45,14 +45,32 @@ static int gpio_wdt_start(struct udevice *dev, u64 timeout, ulong flags)
>   	if (priv->always_running)
>   		return 0;
>   
> -	return -ENOSYS;
> +	dm_gpio_set_dir_flags(&priv->gpio, GPIOD_IS_OUT);
> +	gpio_wdt_reset(dev);
> +
> +	return 0;
> +}
> +
> +static int gpio_wdt_stop(struct udevice *dev)
> +{
> +	struct gpio_wdt_priv *priv = dev_get_priv(dev);
> +
> +	if (priv->always_running)
> +		return -EOPNOTSUPP;
> +
> +	if (priv->hw_algo == HW_ALGO_TOGGLE)
> +		dm_gpio_set_dir_flags(&priv->gpio, GPIOD_IS_IN);
> +	else
> +		dm_gpio_set_value(&priv->gpio, 1);
> +
> +	return 0;
>   }
>   
>   static int dm_probe(struct udevice *dev)
>   {
>   	struct gpio_wdt_priv *priv = dev_get_priv(dev);
> -	int ret;
>   	const char *algo = dev_read_string(dev, "hw_algo");
> +	int ret, flags;
>   
>   	if (!algo)
>   		return -EINVAL;
> @@ -64,7 +82,9 @@ static int dm_probe(struct udevice *dev)
>   		return -EINVAL;
>   
>   	priv->always_running = dev_read_bool(dev, "always-running");
> -	ret = gpio_request_by_name(dev, "gpios", 0, &priv->gpio, GPIOD_IS_OUT);
> +	flags = priv->always_running || priv->hw_algo == HW_ALGO_LEVEL ?
> +		GPIOD_IS_OUT : GPIOD_IS_IN;
> +	ret = gpio_request_by_name(dev, "gpios", 0, &priv->gpio, flags);
>   	if (ret < 0) {
>   		dev_err(dev, "Request for wdt gpio failed: %d\n", ret);
>   		return ret;
> @@ -78,6 +98,7 @@ static int dm_probe(struct udevice *dev)
>   
>   static const struct wdt_ops gpio_wdt_ops = {
>   	.start = gpio_wdt_start,
> +	.stop  = gpio_wdt_stop,
>   	.reset = gpio_wdt_reset,
>   };
>   

Viele Grüße,
Stefan Roese

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