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

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Date:   Mon, 24 Feb 2020 11:22:11 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Anson Huang <Anson.Huang@....com>
Cc:     wim@...ux-watchdog.org, linux@...ck-us.net, shawnguo@...nel.org,
        s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
        linux-watchdog@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Linux-imx@....com
Subject: Re: [PATCH] watchdog: imx2_wdt: Drop .remove callback

On Mon, Feb 24, 2020 at 10:51:27AM +0800, Anson Huang wrote:
> .remove callback implementation doesn' call clk_disable_unprepare() which
> is buggy, actually, we can just use devm_watchdog_register_device() and
> devm_add_action_or_reset() to handle all necessary operations for remove
> action, then .remove callback can be dropped.
> 
> Signed-off-by: Anson Huang <Anson.Huang@....com>
> ---
>  drivers/watchdog/imx2_wdt.c | 37 ++++++++++---------------------------
>  1 file changed, 10 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
> index f8d58bf..1fe472f 100644
> --- a/drivers/watchdog/imx2_wdt.c
> +++ b/drivers/watchdog/imx2_wdt.c
> @@ -244,6 +244,11 @@ static const struct regmap_config imx2_wdt_regmap_config = {
>  	.max_register = 0x8,
>  };
>  
> +static void imx2_wdt_action(void *data)
> +{
> +	clk_disable_unprepare(data);

Does this have the effect of stopping the watchdog? Maybe we can have a
more expressive function name here (imx2_wdt_stop_clk or similar)?

Is there some watchdog core policy that tells if the watchdog should be
stopped on unload?

> +}
> +
>  static int __init imx2_wdt_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
> @@ -292,6 +297,10 @@ static int __init imx2_wdt_probe(struct platform_device *pdev)
>  	if (ret)
>  		return ret;
>  
> +	ret = devm_add_action_or_reset(dev, imx2_wdt_action, wdev->clk);
> +	if (ret)
> +		return ret;
> +
>  	regmap_read(wdev->regmap, IMX2_WDT_WRSR, &val);
>  	wdog->bootstatus = val & IMX2_WDT_WRSR_TOUT ? WDIOF_CARDRESET : 0;
>  
> @@ -315,32 +324,7 @@ static int __init imx2_wdt_probe(struct platform_device *pdev)
>  	 */
>  	regmap_write(wdev->regmap, IMX2_WDT_WMCR, 0);
>  
> -	ret = watchdog_register_device(wdog);
> -	if (ret)
> -		goto disable_clk;
> -
> -	dev_info(dev, "timeout %d sec (nowayout=%d)\n",
> -		 wdog->timeout, nowayout);

Does the core put this info in the kernel log? If not dropping it isn't
obviously right enough to be done en passant.

> -	return 0;
> -
> -disable_clk:
> -	clk_disable_unprepare(wdev->clk);
> -	return ret;
> -}
> -
> -static int __exit imx2_wdt_remove(struct platform_device *pdev)
> -{
> -	struct watchdog_device *wdog = platform_get_drvdata(pdev);
> -	struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);
> -
> -	watchdog_unregister_device(wdog);
> -
> -	if (imx2_wdt_is_running(wdev)) {
> -		imx2_wdt_ping(wdog);
> -		dev_crit(&pdev->dev, "Device removed: Expect reboot!\n");
> -	}

I also wonder about this one. This changes the timing behaviour and so
IMHO shouldn't be done as a side effect of a cleanup patch.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |