Re: [PATCH v1 1/1] driver: watchdog: Add mtk_wdt_init for mediatek watchdog hw init

[Guenter Roeck]

On 8/28/20 12:49 AM, Freddy Hsin wrote:
> 1. add a hw initialization function
> 2. enable/disable the watchdog depends on the original hw setting
> 3. set WDOD_HW_RUNNING in start function in order to start
>    kicker after driver probe and clear the bit in stop function
> 
> Change-Id: I25aa797f3b88288f26984455e499e599e27f09fa
> Signed-off-by: Freddy Hsin <freddy.hsin@xxxxxxxxxxxx>

The subject is misleading - what this really does it to honor
that/if a watchdog is already running. However, WDOG_HW_RUNNING
should not generally be set/cleared in the start/stop function.
Also, calling mtk_wdt_stop is pointless if WDT_MODE_EN is not set,
since clearing WDT_MODE_EN is all it does. On top of that,
setting WDOG_HW_RUNNING in the probe function requires that
max_hw_heartbeat_ms is set (instead of max_timeout).

So if you really want to honor that the watchdog is already running
at boot, you would have to initialize max_hw_heartbeat_ms, set
WDOG_HW_RUNNING explicitly, and possibly call the ping function
before changing the timeout.

Thanks,
Guenter

> ---
>  drivers/watchdog/mtk_wdt.c |   22 +++++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/watchdog/mtk_wdt.c b/drivers/watchdog/mtk_wdt.c
> index d6a6393..59b5061 100644
> --- a/drivers/watchdog/mtk_wdt.c
> +++ b/drivers/watchdog/mtk_wdt.c
> @@ -57,6 +57,9 @@
>  static bool nowayout = WATCHDOG_NOWAYOUT;
>  static unsigned int timeout;
>  
> +static int mtk_wdt_start(struct watchdog_device *wdt_dev);
> +static int mtk_wdt_stop(struct watchdog_device *wdt_dev);
> +
>  struct mtk_wdt_dev {
>  	struct watchdog_device wdt_dev;
>  	void __iomem *wdt_base;
> @@ -148,6 +151,19 @@ static int toprgu_register_reset_controller(struct platform_device *pdev,
>  	return ret;
>  }
>  
> +static int 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)
> +		mtk_wdt_start(wdt_dev);
> +	else
> +		mtk_wdt_stop(wdt_dev);
> +}
> +
>  static int mtk_wdt_restart(struct watchdog_device *wdt_dev,
>  			   unsigned long action, void *data)
>  {
> @@ -206,6 +222,8 @@ static int mtk_wdt_stop(struct watchdog_device *wdt_dev)
>  	reg |= WDT_MODE_KEY;
>  	iowrite32(reg, wdt_base + WDT_MODE);
>  
> +	clear_bit(WDOG_HW_RUNNING, &wdt_dev->status);
> +
>  	return 0;
>  }
>  
> @@ -225,6 +243,8 @@ static int mtk_wdt_start(struct watchdog_device *wdt_dev)
>  	reg |= (WDT_MODE_EN | WDT_MODE_KEY);
>  	iowrite32(reg, wdt_base + WDT_MODE);
>  
> +	set_bit(WDOG_HW_RUNNING, &wdt_dev->status);
> +
>  	return 0;
>  }
>  
> @@ -274,7 +294,7 @@ static int mtk_wdt_probe(struct platform_device *pdev)
>  
>  	watchdog_set_drvdata(&mtk_wdt->wdt_dev, mtk_wdt);
>  
> -	mtk_wdt_stop(&mtk_wdt->wdt_dev);
> +	mtk_wdt_init(&mtk_wdt->wdt_dev);
>  
>  	watchdog_stop_on_reboot(&mtk_wdt->wdt_dev);
>  	err = devm_watchdog_register_device(dev, &mtk_wdt->wdt_dev);
>