linux-kernel - Re: [PATCHv2] watchdog: qcom: Add suspend/resume support

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Date:   Thu, 17 Jan 2019 14:14:10 -0700
From:   Jerry Hoemann <jerry.hoemann@....com>
To:     Guenter Roeck <groeck@...gle.com>
Cc:     Stephen Boyd <swboyd@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        linux-watchdog@...r.kernel.org,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        Sibi Sankar <sibis@...eaurora.org>,
        Doug Anderson <dianders@...omium.org>,
        linux-arm-kernel@...ts.infradead.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCHv2] watchdog: qcom: Add suspend/resume support

On Thu, Jan 17, 2019 at 11:09:31AM -0800, Guenter Roeck wrote:
> On Thu, Jan 17, 2019 at 10:37 AM Stephen Boyd <swboyd@...omium.org> wrote:
> >
> > Quoting Sai Prakash Ranjan (2019-01-17 07:19:42)
> > > diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
> > > index 780971318810..5dfd604477a4 100644
> > > --- a/drivers/watchdog/qcom-wdt.c
> > > +++ b/drivers/watchdog/qcom-wdt.c
> > > @@ -245,6 +245,28 @@ static int qcom_wdt_remove(struct platform_device *pdev)
> > >         return 0;
> > >  }
> > >
> > > +static int __maybe_unused qcom_wdt_suspend(struct device *dev)
> > > +{
> > > +       struct qcom_wdt *wdt = dev_get_drvdata(dev);
> > > +
> > > +       if (watchdog_active(&wdt->wdd))
> > > +               qcom_wdt_stop(&wdt->wdd);
> > > +
> > > +       return 0;
> > > +}
> > > +
> > > +static int __maybe_unused qcom_wdt_resume(struct device *dev)
> > > +{
> > > +       struct qcom_wdt *wdt = dev_get_drvdata(dev);
> > > +
> > > +       if (watchdog_active(&wdt->wdd))
> > > +               qcom_wdt_start(&wdt->wdd);
> > > +
> > > +       return 0;
> > > +}
> >
> > This looks fairly generic. For example, the Mediatek driver also stops
> > and starts (but also pings after starting). Grepping for 'active' in
> > drivers/watchdog/ finds more examples. Could there be some functions in
> > watchdog core that do the common things like watchdog_stop() and
> > watchdog_start() and watchdog_start_and_ping()? Or maybe a bit can be
> > set during registration so that the 'struct class watchdog_class' can
> > get PM ops to stop and start on suspend/resume of the watchdog character
> > device?
> >
> > Nothing is wrong with the patch, I'm just bemoaning the amount of code
> > duplication here.
> >
> 
> Patch(es) to add the functionality to the watchdog core are welcome;
> it should be possible to move the functionality into the core (maybe
> to be enabled with a new watchdog API call). Doing it using the class
> device sounds like an excellent idea. This should be straightforward
> to implement, though the question of "should we ping on resume or not"
> might be an endless source for bike shedding fun.
> 
> Guenter

It could be controlled by a currently unused bit in the
watchdog_info.options.  Then people can agree to disagree.



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Jerry Hoemann                  Software Engineer   Hewlett Packard Enterprise
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