From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from bh-25.webhostbox.net ([208.91.199.152]:50468 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752968AbdERNu7 (ORCPT ); Thu, 18 May 2017 09:50:59 -0400 Subject: Re: [PATCH v2] watchdog: gpio: Add "keep-armed-on-close" feature To: Sylvain Lemieux Cc: wim@iguana.be, linux-watchdog@vger.kernel.org References: <20170314141111.24888-1-slemieux.tyco@gmail.com> <1490885209.26136.14.camel@gmail.com> <1495112471.12459.4.camel@gmail.com> From: Guenter Roeck Message-ID: <9edc91e9-2878-eab5-157f-8b74bd6ed267@roeck-us.net> Date: Thu, 18 May 2017 06:50:56 -0700 MIME-Version: 1.0 In-Reply-To: <1495112471.12459.4.camel@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-watchdog-owner@vger.kernel.org List-Id: linux-watchdog@vger.kernel.org On 05/18/2017 06:01 AM, Sylvain Lemieux wrote: > On Thu, 2017-03-30 at 10:46 -0400, Sylvain Lemieux wrote: >> Hi, >> >> On Thu, 2017-03-30 at 06:11 -0700, Guenter Roeck wrote: >>> On 03/14/2017 07:11 AM, Sylvain Lemieux wrote: >>>> From: Sylvain Lemieux >>>> >>>> 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. >>> >> I will need to send a new version with an updated description; >> > I will submit v3 later today or tomorrow. > >> I did not update the description after this patch was rebased on-top >> of the "watchdog: gpio: keepalives" patch. >> >>> 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. >>> > Do you want me to work on a generic version for this option? > I am not sure I understand the value of the current version (as implemented) in the first place. It seems to be similar to "always-running", with the exception that it doesn't start the watchdog immediately when loading the module. That means it protects the system against hard lockups, but only if the watchdog was opened at least once. That just seems odd, and you'll have to explain the benefit over "always-running", and why it would make sense to have such a selective protection. Note that devicetree property changes need to be Acked by DT maintainers. Having said that, if what you want is what the description says, not what is implemented, I'll be happy to accept a patch to change the infrastructure accordingly. Thanks, Guenter > Sylvain > >>> 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. >> > [...] >> >> Sylvain >>> >>> Guenter >>> >>>> Signed-off-by: Sylvain Lemieux >>>> --- >>>> * 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); >>>> >>>> >>> >> >> > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-watchdog" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >