Re: [PATCH v1 1/1] driver: watchdog: Remove mtk_wdt_stop() in probe() to prevent the system freeze and it doesn't reboot by watchdog problem

[Guenter Roeck]

On 12/24/20 11:30 PM, Freddy Hsin wrote:
> From: "freddy.hsin" <freddy.hsin@xxxxxxxxxxxx>
> 
> Before user space daemon start to access the watchdog device,
> there is a time interval that watchdog is disabled in the
> original flow. If the system freezing at this interval, it
> cannot be rebooted by watchdog hardware automatically.
> 
> In order to solve this problem, the watchdog hardware should be
> kept working, and start hrtimer in framework to ping it by
> setting max_hw_heartbeat_ms and HW_RUNNING used in
> watchdog_need_worker to determine whether the worker should be
> started or not
> 
> Change-Id: I6a041b0922888a90011d7538ee804d80bc8d15ea
> Signed-off-by: freddy.hsin <freddy.hsin@xxxxxxxxxxxx>
> ---
>  drivers/watchdog/mtk_wdt.c |   22 ++++++++++++++++++----
>  1 file changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/watchdog/mtk_wdt.c b/drivers/watchdog/mtk_wdt.c
> index d6a6393..62f08cd 100644
> --- a/drivers/watchdog/mtk_wdt.c
> +++ b/drivers/watchdog/mtk_wdt.c
> @@ -195,6 +195,19 @@ static int mtk_wdt_set_timeout(struct watchdog_device *wdt_dev,
>  	return 0;
>  }
>  
> +static void mtk_wdt_init(struct watchdog_device *wdt_dev)
> +{
> +	struct mtk_wdt_dev *mtk_wdt = watchdog_get_drvdata(wdt_dev);
> +	void __iomem *wdt_base;
> +
> +	wdt_base = mtk_wdt->wdt_base;
> +
> +	if (readl(wdt_base + WDT_MODE) & WDT_MODE_EN) {
> +		set_bit(WDOG_HW_RUNNING, &wdt_dev->status);
> +		mtk_wdt_set_timeout(wdt_dev, wdt_dev->timeout);
> +	}
> +}
> +
>  static int mtk_wdt_stop(struct watchdog_device *wdt_dev)
>  {
>  	struct mtk_wdt_dev *mtk_wdt = watchdog_get_drvdata(wdt_dev);
> @@ -266,16 +279,17 @@ static int mtk_wdt_probe(struct platform_device *pdev)
>  	mtk_wdt->wdt_dev.timeout = WDT_MAX_TIMEOUT;
>  	mtk_wdt->wdt_dev.max_timeout = WDT_MAX_TIMEOUT;

No longer needed if max_hw_heartbeat_ms is set.

>  	mtk_wdt->wdt_dev.min_timeout = WDT_MIN_TIMEOUT;
> +	mtk_wdt->wdt_dev.max_hw_heartbeat_ms = (WDT_MAX_TIMEOUT - 1) * 1000;

This needs explanation. Why WDT_MAX_TIMEOUT - 1 ?

>  	mtk_wdt->wdt_dev.parent = dev;
>  
> +	watchdog_set_drvdata(&mtk_wdt->wdt_dev, mtk_wdt);
> +
> +	mtk_wdt_init(&mtk_wdt->wdt_dev);
> +

Setting the chip (with the maximum timeout) ...

>  	watchdog_init_timeout(&mtk_wdt->wdt_dev, timeout, dev);

just before initializing/setting the real timeout doesn't really make sense.

>  	watchdog_set_nowayout(&mtk_wdt->wdt_dev, nowayout);
>  	watchdog_set_restart_priority(&mtk_wdt->wdt_dev, 128);
>  
> -	watchdog_set_drvdata(&mtk_wdt->wdt_dev, mtk_wdt);
> -
> -	mtk_wdt_stop(&mtk_wdt->wdt_dev);
> -
>  	watchdog_stop_on_reboot(&mtk_wdt->wdt_dev);
>  	err = devm_watchdog_register_device(dev, &mtk_wdt->wdt_dev);
>  	if (unlikely(err))
>