linux-kernel - Re: [PATCH v3] watchdog: imx2

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Date:   Sat, 29 Jan 2022 17:42:26 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Alistair Francis <alistair@...stair23.me>
Cc:     linux-arm-kernel@...ts.infradead.org,
        linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org,
        shawnguo@...nel.org, wim@...ux-watchdog.org,
        s.hauer@...gutronix.de, robh+dt@...nel.org, linux-imx@....com,
        devicetree@...r.kernel.org, kernel@...gutronix.de,
        festevam@...il.com
Subject: Re: [PATCH v3] watchdog: imx2_wdg: Alow ping on suspend

On Thu, Jan 27, 2022 at 08:47:39PM +1000, Alistair Francis wrote:
> The i.MX watchdog cannot be disabled by software once it has been
> enabled. This means that it can't be stopped before suspend.
> 
> For systems that enter low power mode this is fine, as the watchdog will
> be automatically stopped by hardware in low power mode. Not all i.MX
> platforms support low power mode in the mainline kernel. For example the
> i.MX7D does not enter low power mode and so will be rebooted 2 minutes
> after entering sleep states.
> 
> This patch introduces a device tree property "fsl,ping-during-suspend"
> that can be used to enable ping on suspend support for these systems.
> 
> Signed-off-by: Alistair Francis <alistair@...stair23.me>

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

> ---
> v3:
>  - Fixup typos in commit message
> v2:
>  - Remove custom property
> 
>  drivers/watchdog/imx2_wdt.c | 27 ++++++++++++++++++++-------
>  1 file changed, 20 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
> index 51bfb796898b..d0c5d47ddede 100644
> --- a/drivers/watchdog/imx2_wdt.c
> +++ b/drivers/watchdog/imx2_wdt.c
> @@ -66,6 +66,7 @@ struct imx2_wdt_device {
>  	struct watchdog_device wdog;
>  	bool ext_reset;
>  	bool clk_is_on;
> +	bool no_ping;
>  };
>  
>  static bool nowayout = WATCHDOG_NOWAYOUT;
> @@ -312,12 +313,18 @@ static int __init imx2_wdt_probe(struct platform_device *pdev)
>  
>  	wdev->ext_reset = of_property_read_bool(dev->of_node,
>  						"fsl,ext-reset-output");
> +	/*
> +	 * The i.MX7D doesn't support low power mode, so we need to ping the watchdog
> +	 * during suspend.
> +	 */
> +	wdev->no_ping = !of_device_is_compatible(dev->of_node, "fsl,imx7d-wdt");
>  	platform_set_drvdata(pdev, wdog);
>  	watchdog_set_drvdata(wdog, wdev);
>  	watchdog_set_nowayout(wdog, nowayout);
>  	watchdog_set_restart_priority(wdog, 128);
>  	watchdog_init_timeout(wdog, timeout, dev);
> -	watchdog_stop_ping_on_suspend(wdog);
> +	if (wdev->no_ping)
> +		watchdog_stop_ping_on_suspend(wdog);
>  
>  	if (imx2_wdt_is_running(wdev)) {
>  		imx2_wdt_set_timeout(wdog, wdog->timeout);
> @@ -366,9 +373,11 @@ static int __maybe_unused imx2_wdt_suspend(struct device *dev)
>  		imx2_wdt_ping(wdog);
>  	}
>  
> -	clk_disable_unprepare(wdev->clk);
> +	if (wdev->no_ping) {
> +		clk_disable_unprepare(wdev->clk);
>  
> -	wdev->clk_is_on = false;
> +		wdev->clk_is_on = false;
> +	}
>  
>  	return 0;
>  }
> @@ -380,11 +389,14 @@ static int __maybe_unused imx2_wdt_resume(struct device *dev)
>  	struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);
>  	int ret;
>  
> -	ret = clk_prepare_enable(wdev->clk);
> -	if (ret)
> -		return ret;
> +	if (wdev->no_ping) {
> +		ret = clk_prepare_enable(wdev->clk);
>  
> -	wdev->clk_is_on = true;
> +		if (ret)
> +			return ret;
> +
> +		wdev->clk_is_on = true;
> +	}
>  
>  	if (watchdog_active(wdog) && !imx2_wdt_is_running(wdev)) {
>  		/*
> @@ -407,6 +419,7 @@ static SIMPLE_DEV_PM_OPS(imx2_wdt_pm_ops, imx2_wdt_suspend,
>  
>  static const struct of_device_id imx2_wdt_dt_ids[] = {
>  	{ .compatible = "fsl,imx21-wdt", },
> +	{ .compatible = "fsl,imx7d-wdt", },
>  	{ /* sentinel */ }
>  };
>  MODULE_DEVICE_TABLE(of, imx2_wdt_dt_ids);