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Date: Sun, 07 Sep 2014 10:23:49 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Evgeny Boger <boger@...tactless.ru>,
linux-watchdog@...r.kernel.org,
Alexander Shiyan <shc_work@...l.ru>,
linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2] Add support for always enabled watchdog timers to
gpio_wdt driver
On 09/06/2014 09:47 AM, Evgeny Boger wrote:
> From: Evgeny Boger <boger@...tactless.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.
>
> Signed-off-by: Evgeny Boger <boger@...tactless.ru>
> ---
>
Overall looks good to me, though we really need feedback from the DT folks
on the binding. There is a parallel effort to add this functionality into
the watchdog core, meaning the proposed binding "'always-enabled' will
very likely find its way into other drivers. We'll also need a separate
binding to express "watchdog can not be stopped after started once".
That is a separate issue, but important to keep in mind when discussing
the bindings.
Thanks,
Guenter
> Changes since v1:
> * fixed typos and indentation
> * gpio_wdt_start_timer renamed to gpio_wdt_start_hwping.
> This function actually starts the timer to ping hardware.
> I personally find both proposed gpio_wdt_enable and __gpio_wdt_start
> names discouraging in this context.
> * fixed broken error handling for register_reboot_notifier
>
> .../devicetree/bindings/watchdog/gpio-wdt.txt | 14 ++++++-
> drivers/watchdog/gpio_wdt.c | 46 +++++++++++++++++-----
> 2 files changed, 50 insertions(+), 10 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/watchdog/gpio-wdt.txt b/Documentation/devicetree/bindings/watchdog/gpio-wdt.txt
> index 37afec1..047fe3f 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 watchdog timer which is always enabled
> + 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..b6ab6e7 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;
> };
>
> 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_hwping(struct gpio_wdt_priv *priv)
> {
> - 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 +60,30 @@ static int gpio_wdt_start(struct watchdog_device *wdd)
> return 0;
> }
>
> +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) {
> + /* hardware ping timer is already enabled */
> + priv->last_jiffies = jiffies;
> + } else {
> + gpio_wdt_start_hwping(priv);
> + }
> +
> + return 0;
> +}
> +
> static int gpio_wdt_stop(struct watchdog_device *wdd)
> {
> struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
>
> - mod_timer(&priv->timer, 0);
> - gpio_wdt_disable(priv);
> + priv->started = false;
> + if (!priv->always_enabled) {
> + mod_timer(&priv->timer, 0);
> + gpio_wdt_disable(priv);
> + }
>
> return 0;
> }
> @@ -91,8 +109,9 @@ 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))) {
> + if (priv->started &&
> + time_after(jiffies, priv->last_jiffies +
> + msecs_to_jiffies(wdd->timeout * 1000))) {
> dev_crit(wdd->dev, "Timer expired. System will reboot soon!\n");
> return;
> }
> @@ -197,6 +216,9 @@ 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 +229,7 @@ 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);
> @@ -215,10 +238,15 @@ static int gpio_wdt_probe(struct platform_device *pdev)
>
> priv->notifier.notifier_call = gpio_wdt_notify_sys;
> ret = register_reboot_notifier(&priv->notifier);
> - if (ret)
> + if (ret) {
> watchdog_unregister_device(&priv->wdd);
> + return ret;
> + }
>
> - return ret;
> + if (priv->always_enabled)
> + gpio_wdt_start_hwping(priv);
> +
> + return 0;
> }
>
> static int gpio_wdt_remove(struct platform_device *pdev)
>
--
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