Re: [PATCH v7 1/3] watchdog: renesas_wdt: Add suspend/resume support

[Guenter Roeck <linux@roeck-us.net>]

On Thu, Mar 01, 2018 at 06:17:21PM +0000, Fabrizio Castro wrote:
> On R-Car Gen2 and RZ/G1 the watchdog IP clock needs to be always ON,
> on R-Car Gen3 we power the IP down during suspend.
> 
> This commit adds suspend/resume support, so that the watchdog counting
> "pauses" during suspend on all of the SoCs compatible with this driver
> and on those we are now adding support for (R-Car Gen2 and RZ/G1).
> 
> Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
> Signed-off-by: Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com>

Usually, on resume, we just restart the watchdog, with the expectation in mind
that there may be some delay in userspace before it gets to send the next ping.
Presumably that is not a concern here, so

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
> v6->v7:
> * backup and restore register RWTCNT instead of using rwdt_get_timeleft and
>   rwdt_set_timeleft
> 
>  drivers/watchdog/renesas_wdt.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/drivers/watchdog/renesas_wdt.c b/drivers/watchdog/renesas_wdt.c
> index 831ef83..024d54e 100644
> --- a/drivers/watchdog/renesas_wdt.c
> +++ b/drivers/watchdog/renesas_wdt.c
> @@ -49,6 +49,7 @@ struct rwdt_priv {
>  	void __iomem *base;
>  	struct watchdog_device wdev;
>  	unsigned long clk_rate;
> +	u16 time_left;
>  	u8 cks;
>  };
>  
> @@ -203,6 +204,30 @@ static int rwdt_remove(struct platform_device *pdev)
>  	return 0;
>  }
>  
> +static int __maybe_unused rwdt_suspend(struct device *dev)
> +{
> +	struct rwdt_priv *priv = dev_get_drvdata(dev);
> +
> +	if (watchdog_active(&priv->wdev)) {
> +		priv->time_left = readw(priv->base + RWTCNT);
> +		rwdt_stop(&priv->wdev);
> +	}
> +	return 0;
> +}
> +
> +static int __maybe_unused rwdt_resume(struct device *dev)
> +{
> +	struct rwdt_priv *priv = dev_get_drvdata(dev);
> +
> +	if (watchdog_active(&priv->wdev)) {
> +		rwdt_start(&priv->wdev);
> +		rwdt_write(priv, priv->time_left, RWTCNT);
> +	}
> +	return 0;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(rwdt_pm_ops, rwdt_suspend, rwdt_resume);
> +
>  /*
>   * This driver does also fit for R-Car Gen2 (r8a779[0-4]) WDT. However, for SMP
>   * to work there, one also needs a RESET (RST) driver which does not exist yet
> @@ -218,6 +243,7 @@ static struct platform_driver rwdt_driver = {
>  	.driver = {
>  		.name = "renesas_wdt",
>  		.of_match_table = rwdt_ids,
> +		.pm = &rwdt_pm_ops,
>  	},
>  	.probe = rwdt_probe,
>  	.remove = rwdt_remove,
> -- 
> 2.7.4
>