linux-kernel - Re: [PATCH 07/10] watchdog: rzg2l

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Message-ID: <20240122210553.GA2731@perchik>
Date: Mon, 22 Jan 2024 14:05:53 -0700
From: Jerry Hoemann <jerry.hoemann@....com>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Claudiu <claudiu.beznea@...on.dev>, wim@...ux-watchdog.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, geert+renesas@...der.be, magnus.damm@...il.com,
        mturquette@...libre.com, sboyd@...nel.org, p.zabel@...gutronix.de,
        biju.das.jz@...renesas.com, linux-watchdog@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org, linux-clk@...r.kernel.org,
        Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH 07/10] watchdog: rzg2l_wdt: Add suspend/resume support

On Mon, Jan 22, 2024 at 09:39:27AM -0800, Guenter Roeck wrote:
> On 1/22/24 03:11, Claudiu wrote:
> > From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> > 
> > The RZ/G3S supports deep sleep states where power to most of the IP blocks
> > is cut off. To ensure proper working of the watchdog when resuming from
> > such states, the suspend function is stopping the watchdog and the resume
> > function is starting it. There is no need to configure the watchdog
> > in case the watchdog was stopped prior to starting suspend.
> > 
> > Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> > ---
> >   drivers/watchdog/rzg2l_wdt.c | 26 ++++++++++++++++++++++++++
> >   1 file changed, 26 insertions(+)
> > 
> > diff --git a/drivers/watchdog/rzg2l_wdt.c b/drivers/watchdog/rzg2l_wdt.c
> > index 9333dc1a75ab..186796b739f7 100644
> > --- a/drivers/watchdog/rzg2l_wdt.c
> > +++ b/drivers/watchdog/rzg2l_wdt.c
> > @@ -279,6 +279,7 @@ static int rzg2l_wdt_probe(struct platform_device *pdev)
> >   	priv->wdev.timeout = WDT_DEFAULT_TIMEOUT;
> >   	watchdog_set_drvdata(&priv->wdev, priv);
> > +	dev_set_drvdata(dev, priv);
> >   	ret = devm_add_action_or_reset(&pdev->dev, rzg2l_wdt_pm_disable, &priv->wdev);
> >   	if (ret)
> >   		return ret;
> > @@ -300,10 +301,35 @@ static const struct of_device_id rzg2l_wdt_ids[] = {
> >   };
> >   MODULE_DEVICE_TABLE(of, rzg2l_wdt_ids);
> > +static int rzg2l_wdt_suspend_late(struct device *dev)
> > +{
> > +	struct rzg2l_wdt_priv *priv = dev_get_drvdata(dev);
> > +
> > +	if (!watchdog_active(&priv->wdev))
> > +		return 0;
> > +
> > +	return rzg2l_wdt_stop(&priv->wdev);
> > +}
> > +
> > +static int rzg2l_wdt_resume_early(struct device *dev)
> > +{
> > +	struct rzg2l_wdt_priv *priv = dev_get_drvdata(dev);
> > +
> > +	if (!watchdog_active(&priv->wdev))
> > +		return 0;
> > +
> > +	return rzg2l_wdt_start(&priv->wdev);
> > +}
> > +
> > +static const struct dev_pm_ops rzg2l_wdt_pm_ops = {
> > +	LATE_SYSTEM_SLEEP_PM_OPS(rzg2l_wdt_suspend_late, rzg2l_wdt_resume_early)
> > +};
> > +
> >   static struct platform_driver rzg2l_wdt_driver = {
> >   	.driver = {
> >   		.name = "rzg2l_wdt",
> >   		.of_match_table = rzg2l_wdt_ids,
> > +		.pm = pm_ptr(&rzg2l_wdt_pm_ops),
> 
> I think this will create a build error if CONFIG_PM=n because rzg2l_wdt_pm_ops
> will be unused but is not marked with __maybe_unused. But then the driver won't be
> operational with CONFIG_PM=n, so I really wonder if it makes sense to include any
> such conditional code instead of making the driver depend on CONFIG_PM.
> 
> I really don't think it is desirable to suggest that the driver would work with
> CONFIG_PM=n if that isn't really true.
> 
> Guenter

Guenter,

I'm working on a similar patch.

Is your concern limited to the use of the "pm_ptr" macro?  Or is it
wider?

Thanks

Jerry

-- 

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Jerry Hoemann                  Software Engineer   Hewlett Packard Enterprise
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