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SubjectRe: [PATCH] Add support for always enabled watchdog timers
On 08/16/2014 05:45 PM, Evgeny Boger wrote:
> From: Evgeny Boger <boger@contactless.ru>
>
> Add option to use with watchdog timers which are always enabled
> in hardware, i.e. there is no way to enable/disable it via GPIO pin.
> The driver will start pinging WDT immediately upon loading
> and will continue to do so even after stopping the watchdog.
>
The headline needs a reference to the affected driver.

Also, please copy the dt mailing list and maintainers.

> Signed-off-by: Evgeny Boger <boger@contactless.ru>
> ---
> .../devicetree/bindings/watchdog/gpio-wdt.txt | 14 ++++++-
> drivers/watchdog/gpio_wdt.c | 45 +++++++++++++++++-----
> 2 files changed, 48 insertions(+), 11 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/watchdog/gpio-wdt.txt b/Documentation/devicetree/bindings/watchdog/gpio-wdt.txt
> index 37afec1..1f8ca46 100644
> --- a/Documentation/devicetree/bindings/watchdog/gpio-wdt.txt
> +++ b/Documentation/devicetree/bindings/watchdog/gpio-wdt.txt
> @@ -12,8 +12,11 @@ Required Properties:
> the opposite level disables the WDT. Active level is determined
> by the GPIO flags.
> - hw_margin_ms: Maximum time to reset watchdog circuit (milliseconds).
> +- always-enabled: Use with wathdog timer which is always enabled

s/wathdog/watchdog/

> + in hardware, i.e. there is no way to enable/disable it via GPIO pin.
> + Driver will start pinging WDT immediately upon loading.
>
> -Example:
> +Examples:
> watchdog: watchdog {
> /* ADM706 */
> compatible = "linux,wdt-gpio";
> @@ -21,3 +24,12 @@ Example:
> hw_algo = "toggle";
> hw_margin_ms = <1600>;
> };
> +
> + watchdog: watchdog {
> + /* TPS3813 */
> + compatible = "linux,wdt-gpio";
> + gpios = <&gpio3 9 GPIO_ACTIVE_LOW>;
> + hw_algo = "toggle";
> + hw_margin_ms = <10000>;
> + always-enabled;
> + };
> diff --git a/drivers/watchdog/gpio_wdt.c b/drivers/watchdog/gpio_wdt.c
> index 220a9e0..29f9bff 100644
> --- a/drivers/watchdog/gpio_wdt.c
> +++ b/drivers/watchdog/gpio_wdt.c
> @@ -37,6 +37,8 @@ struct gpio_wdt_priv {
> struct notifier_block notifier;
> struct timer_list timer;
> struct watchdog_device wdd;
> + bool always_enabled;
> + bool started;

Please keep indentation aligned with existing code.

> };
>
> static void gpio_wdt_disable(struct gpio_wdt_priv *priv)
> @@ -48,10 +50,8 @@ static void gpio_wdt_disable(struct gpio_wdt_priv *priv)
> gpio_direction_input(priv->gpio);
> }
>
> -static int gpio_wdt_start(struct watchdog_device *wdd)
> +static int gpio_wdt_start_timer(struct gpio_wdt_priv *priv)

Unfortunate function name. gpio_wdt_enable would be more appropriate,
or maybe __gpio_wdt_start.

> {
> - struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
> -
> priv->state = priv->active_low;
> gpio_direction_output(priv->gpio, priv->state);
> priv->last_jiffies = jiffies;
> @@ -60,12 +60,28 @@ static int gpio_wdt_start(struct watchdog_device *wdd)
> return 0;
> }
>
> -static int gpio_wdt_stop(struct watchdog_device *wdd)
> +static int gpio_wdt_start(struct watchdog_device *wdd)
> {
> struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
> + priv->started = true;
> + if (priv->always_enabled) {
> + /* harware ping timer is already enabled */

s/harware/hardware/

> + priv->last_jiffies = jiffies;
> + } else {
> + gpio_wdt_start_timer(priv);
> + }
>
> - mod_timer(&priv->timer, 0);
> - gpio_wdt_disable(priv);
> + return 0;
> +}
> +
> +static int gpio_wdt_stop(struct watchdog_device *wdd)
> +{
> + struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
> + priv->started = false;
> + if (!priv->always_enabled) {
> + mod_timer(&priv->timer, 0);
> + gpio_wdt_disable(priv);
> + }
>
> return 0;
> }
> @@ -91,10 +107,12 @@ static void gpio_wdt_hwping(unsigned long data)
> struct watchdog_device *wdd = (struct watchdog_device *)data;
> struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
>
> - if (time_after(jiffies, priv->last_jiffies +
> - msecs_to_jiffies(wdd->timeout * 1000))) {
> - dev_crit(wdd->dev, "Timer expired. System will reboot soon!\n");
> - return;
> + if (priv->started) {
> + if (time_after(jiffies, priv->last_jiffies +
> + msecs_to_jiffies(wdd->timeout * 1000))) {
> + dev_crit(wdd->dev, "Timer expired. System will reboot soon!\n");
> + return;
> + }

No need to add another if and indentation level. Just make it

if (priv->started &&
time_after(jiffies, priv->last_jiffies +
...


> }
>
> /* Restart timer */
> @@ -197,6 +215,9 @@ static int gpio_wdt_probe(struct platform_device *pdev)
> /* Use safe value (1/2 of real timeout) */
> priv->hw_margin = msecs_to_jiffies(hw_margin / 2);
>
> + priv->always_enabled = of_property_read_bool(pdev->dev.of_node,
> + "always-enabled");
> +
> watchdog_set_drvdata(&priv->wdd, priv);
>
> priv->wdd.info = &gpio_wdt_ident;
> @@ -207,6 +228,7 @@ static int gpio_wdt_probe(struct platform_device *pdev)
> if (watchdog_init_timeout(&priv->wdd, 0, &pdev->dev) < 0)
> priv->wdd.timeout = SOFT_TIMEOUT_DEF;
>
> + priv->started = false;
> setup_timer(&priv->timer, gpio_wdt_hwping, (unsigned long)&priv->wdd);
>
> ret = watchdog_register_device(&priv->wdd);
> @@ -218,6 +240,9 @@ static int gpio_wdt_probe(struct platform_device *pdev)
> if (ret)
> watchdog_unregister_device(&priv->wdd);
>
> + if (priv->always_enabled)
> + gpio_wdt_start_timer(priv);
> +

This will cause a problem if register_reboot_notifier failed. You'll have
to implement proper error handling for this case, something like the following.

...
priv->notifier.notifier_call = gpio_wdt_notify_sys;
ret = register_reboot_notifier(&priv->notifier);
if (ret)
goto unregister;

if (priv->always_enabled)
gpio_wdt_enable(priv);

return 0;

unregister:
watchdog_unregister_device(&priv->wdd);
return ret;
}

Guenter


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