On 03/14/2017 07:11 AM, Sylvain Lemieux wrote:
From: Sylvain Lemieux <slemieux@xxxxxxxxxxx> There is a need to allow a grace period after the watchdog software client has closed. It could be used for syncing the filesystem or allow graceful termination while still providing a hardware reset in case the system has hung. The "always-running" configuration from device-tree does not provide this since it will automatically keep the hardware watchdog alive as soon as the software client closes (i.e. keep toggling the GPIO line regardless of the state of the soft part of the watchdog). The "keep-armed-on-close" member in the GPIO watchdog implementation indicates if an expired timeout should cause a reset. This patch add a new "keep-armed-on-close" device-tree configuration that will keep the watchdog "armed" until the next timeout period after a close. During this period, the hardware watchdog is kept alive. A software watchdog client that wants to provide a grace period before a hard reset can set the timeout before properly closing.
The description doesn't match what the code actually does, at least from an infrastructure perspective. The infrastructure would just keep it running. What you are really asking for is something the infrastructure should possibly do by itself automatically: To keep pinging a HW watchdog after close until the configured (software) timeout period expires. This would be in line with expectations. Also, I seem to recall that the gpio_wdt patch this relies on has a problem if the watchdog is opened and closed repeatedly. It is still on my task list to track this down. Guenter
Signed-off-by: Sylvain Lemieux <slemieux@xxxxxxxxxxx> --- * This patch depend on the: "watchdog: gpio: Convert to use infrastructure triggered keepalives"; ref. https://lkml.org/lkml/2016/2/28/239 (version 8) Changes from v1 to v2: * Rebased on-top of the "watchdog: gpio: keepalives" patch. - Updated the management of the "WDOG_HW_RUNNING" flag. * Tested with v4.11-rc1. Documentation/devicetree/bindings/watchdog/gpio-wdt.txt | 3 +++ drivers/watchdog/gpio_wdt.c | 10 ++++++++++ 2 files changed, 13 insertions(+) diff --git a/Documentation/devicetree/bindings/watchdog/gpio-wdt.txt b/Documentation/devicetree/bindings/watchdog/gpio-wdt.txt index 83d28146e39b..48db076771b2 100644 --- a/Documentation/devicetree/bindings/watchdog/gpio-wdt.txt +++ b/Documentation/devicetree/bindings/watchdog/gpio-wdt.txt @@ -17,6 +17,9 @@ Optional Properties: - always-running: If the watchdog timer cannot be disabled, add this flag to have the driver keep toggling the signal without a client. It will only cease to toggle the signal when the device is open and the timeout elapsed. +- keep-armed-on-close: if the watchdog timer need to keep toggling the signal + when close, until the timeout elapsed, add this flag to have the driver + keep toggling the signal, until the timeout elapsed. - timeout-sec: Contains the watchdog timeout in seconds. - start-at-init: Start kicking watchdog as soon as driver is loaded. diff --git a/drivers/watchdog/gpio_wdt.c b/drivers/watchdog/gpio_wdt.c index 7b46d224cb56..2f4799bee9bd 100644 --- a/drivers/watchdog/gpio_wdt.c +++ b/drivers/watchdog/gpio_wdt.c @@ -29,6 +29,7 @@ struct gpio_wdt_priv { bool active_low; bool state; bool always_running; + bool keep_armed_on_close; unsigned int hw_algo; struct watchdog_device wdd; }; @@ -78,6 +79,13 @@ static int gpio_wdt_stop(struct watchdog_device *wdd) { struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd); + if(priv->keep_armed_on_close) { + /* Keep the driver running on close. */ + set_bit(WDOG_HW_RUNNING, &wdd->status); + + return 0; + } + if (!priv->always_running) { gpio_wdt_disable(priv); clear_bit(WDOG_HW_RUNNING, &wdd->status); @@ -148,6 +156,8 @@ static int gpio_wdt_probe(struct platform_device *pdev) priv->always_running = of_property_read_bool(pdev->dev.of_node, "always-running"); + priv->keep_armed_on_close = of_property_read_bool(pdev->dev.of_node, + "keep-armed-on-close"); watchdog_set_drvdata(&priv->wdd, priv);
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