linux-kernel - Re: [PATCH v5] watchdog: imx2

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Date:   Thu, 31 Mar 2022 19:47:48 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Alistair Francis <alistair@...stair23.me>, wim@...ux-watchdog.org,
        linux-kernel@...r.kernel.org, shawnguo@...nel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-watchdog@...r.kernel.org, s.hauer@...gutronix.de
Cc:     festevam@...il.com, kernel@...gutronix.de, linux-imx@....com,
        robh+dt@...nel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v5] watchdog: imx2_wdg: Allow ping on suspend

On 3/30/22 02:45, 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 the "fsl,imx7d-wdt" compatible string
> which enables ping on suspend support. This allows the i.MX7D systems to
> suspend without triggering the watchdog.
> 
> Signed-off-by: Alistair Francis <alistair@...stair23.me>
> Reviewed-by: Guenter Roeck <linux@...ck-us.net>
> ---
> v5:
>   - Fixup commit message description

Too late ;-)

Guenter

> v4:
>   - Fix spelling on allow/alow in title
> 
>   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);