linux-kernel - Re: [PATCH 2/2] watchdog: rti: tweak min_hw_heartbeat

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Date:   Wed, 24 Jun 2020 17:24:05 +0200
From:   Jan Kiszka <jan.kiszka@...mens.com>
To:     Tero Kristo <t-kristo@...com>, wim@...ux-watchdog.org,
        linux@...ck-us.net, linux-watchdog@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] watchdog: rti: tweak min_hw_heartbeat_ms to match
 initial allowed window

On 24.06.20 13:45, Tero Kristo wrote:
> If the RTI watchdog has been started by someone (like bootloader) when
> the driver probes, we must adjust the initial ping timeout to match the
> currently running watchdog window to avoid generating watchdog reset.
> 
> Signed-off-by: Tero Kristo <t-kristo@...com>
> ---
>   drivers/watchdog/rti_wdt.c | 25 +++++++++++++++++++++++++
>   1 file changed, 25 insertions(+)
> 
> diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
> index d456dd72d99a..02ea2b2435f5 100644
> --- a/drivers/watchdog/rti_wdt.c
> +++ b/drivers/watchdog/rti_wdt.c
> @@ -55,11 +55,13 @@ static int heartbeat;
>    * @base - base io address of WD device
>    * @freq - source clock frequency of WDT
>    * @wdd  - hold watchdog device as is in WDT core
> + * @min_hw_heartbeat_save - save of the min hw heartbeat value
>    */
>   struct rti_wdt_device {
>   	void __iomem		*base;
>   	unsigned long		freq;
>   	struct watchdog_device	wdd;
> +	unsigned int		min_hw_heartbeat_save;
>   };
>   
>   static int rti_wdt_start(struct watchdog_device *wdd)
> @@ -107,6 +109,11 @@ static int rti_wdt_ping(struct watchdog_device *wdd)
>   	/* put watchdog in active state */
>   	writel_relaxed(WDKEY_SEQ1, wdt->base + RTIWDKEY);
>   
> +	if (wdt->min_hw_heartbeat_save) {
> +		wdd->min_hw_heartbeat_ms = wdt->min_hw_heartbeat_save;
> +		wdt->min_hw_heartbeat_save = 0;
> +	}
> +
>   	return 0;
>   }
>   
> @@ -201,6 +208,24 @@ static int rti_wdt_probe(struct platform_device *pdev)
>   		goto err_iomap;
>   	}
>   
> +	if (readl(wdt->base + RTIDWDCTRL) == WDENABLE_KEY) {
> +		u32 time_left;
> +		u32 heartbeat;
> +
> +		set_bit(WDOG_HW_RUNNING, &wdd->status);
> +		time_left = rti_wdt_get_timeleft(wdd);
> +		heartbeat = readl(wdt->base + RTIDWDPRLD);
> +		heartbeat <<= WDT_PRELOAD_SHIFT;
> +		heartbeat /= wdt->freq;
> +		if (time_left < heartbeat / 2)
> +			wdd->min_hw_heartbeat_ms = 0;
> +		else
> +			wdd->min_hw_heartbeat_ms =
> +				(time_left - heartbeat / 2 + 1) * 1000;
> +
> +		wdt->min_hw_heartbeat_save = 11 * heartbeat * 1000 / 20;
> +	}
> +
>   	ret = watchdog_register_device(wdd);
>   	if (ret) {
>   		dev_err(dev, "cannot register watchdog device\n");
> 

This assumes that the bootloader also programmed a 50% window, right? 
The pending U-Boot patch will do that, but what if that may chance or 
someone uses a different setup?

Jan

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