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Sender: Guenter Roeck <groeck7@gmail.com>
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Date: Mon, 22 Jan 2024 09:39:27 -0800
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Subject: Re: [PATCH 07/10] watchdog: rzg2l_wdt: Add suspend/resume support
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To: Claudiu <claudiu.beznea@tuxon.dev>, wim@linux-watchdog.org,
 robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
 geert+renesas@glider.be, magnus.damm@gmail.com, mturquette@baylibre.com,
 sboyd@kernel.org, p.zabel@pengutronix.de, biju.das.jz@bp.renesas.com
Cc: linux-watchdog@vger.kernel.org, devicetree@vger.kernel.org,
 linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
 linux-clk@vger.kernel.org, Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
References: <20240122111115.2861835-1-claudiu.beznea.uj@bp.renesas.com>
 <20240122111115.2861835-8-claudiu.beznea.uj@bp.renesas.com>
From: Guenter Roeck <linux@roeck-us.net>
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In-Reply-To: <20240122111115.2861835-8-claudiu.beznea.uj@bp.renesas.com>
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On 1/22/24 03:11, Claudiu wrote:
> From: Claudiu Beznea <claudiu.beznea.uj@bp.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@bp.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

>   	},
>   	.probe = rzg2l_wdt_probe,
>   };