linux-kernel - Re: [PATCH v2] watchdog: rti_wdt: Set min_hw_heartbeat

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Date: Fri, 5 Apr 2024 10:11:45 -0300
From: Rafael Beims <rafael@...ms.me>
To: Judith Mendez <jm@...com>, Wim Van Sebroeck <wim@...ux-watchdog.org>,
 Guenter Roeck <linux@...ck-us.net>
Cc: linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org,
 Francesco Dolcini <francesco@...cini.it>
Subject: Re: [PATCH v2] watchdog: rti_wdt: Set min_hw_heartbeat_ms to
 accommodate 5% safety margin

On 04/04/2024 12:33, Judith Mendez wrote:
> On AM62x, the watchdog is pet before the valid window
> is open. Fix min_hw_heartbeat and accommodate a 5% safety
> margin with the exception of open window size < 10%,
> which shall use <5% due to the smaller open window size.
>
> cc: stable@...r.kernel.org
> Fixes: 5527483f8f7c (" watchdog: rti-wdt: attach to running watchdog during probe")
> Signed-off-by: Judith Mendez <jm@...com>
> ---
>   drivers/watchdog/rti_wdt.c | 24 +++++++++++++-----------
>   1 file changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
> index 8e1be7ba0103..0b16ada659cc 100644
> --- a/drivers/watchdog/rti_wdt.c
> +++ b/drivers/watchdog/rti_wdt.c
> @@ -92,7 +92,7 @@ static int rti_wdt_start(struct watchdog_device *wdd)
>   	 * to be 50% or less than that; we obviouly want to configure the open
>   	 * window as large as possible so we select the 50% option.
>   	 */
> -	wdd->min_hw_heartbeat_ms = 500 * wdd->timeout;
> +	wdd->min_hw_heartbeat_ms = 550 * wdd->timeout;
>   
>   	/* Generate NMI when wdt expires */
>   	writel_relaxed(RTIWWDRX_NMI, wdt->base + RTIWWDRXCTRL);
> @@ -126,31 +126,33 @@ static int rti_wdt_setup_hw_hb(struct watchdog_device *wdd, u32 wsize)
>   	 * be petted during the open window; not too early or not too late.
>   	 * The HW configuration options only allow for the open window size
>   	 * to be 50% or less than that.
> +	 * To avoid any glitches, we accommodate 5% safety margin, with the
> +	 * exception of open window size < 10%.
>   	 */
>   	switch (wsize) {
>   	case RTIWWDSIZE_50P:
> -		/* 50% open window => 50% min heartbeat */
> -		wdd->min_hw_heartbeat_ms = 500 * heartbeat;
> +		/* 50% open window => 55% min heartbeat */
> +		wdd->min_hw_heartbeat_ms = 550 * heartbeat;
>   		break;
>   
>   	case RTIWWDSIZE_25P:
> -		/* 25% open window => 75% min heartbeat */
> -		wdd->min_hw_heartbeat_ms = 750 * heartbeat;
> +		/* 25% open window => 80% min heartbeat */
> +		wdd->min_hw_heartbeat_ms = 800 * heartbeat;
>   		break;
>   
>   	case RTIWWDSIZE_12P5:
> -		/* 12.5% open window => 87.5% min heartbeat */
> -		wdd->min_hw_heartbeat_ms = 875 * heartbeat;
> +		/* 12.5% open window => 92.5% min heartbeat */
> +		wdd->min_hw_heartbeat_ms = 925 * heartbeat;
>   		break;
>   
>   	case RTIWWDSIZE_6P25:
> -		/* 6.5% open window => 93.5% min heartbeat */
> -		wdd->min_hw_heartbeat_ms = 935 * heartbeat;
> +		/* 6.5% open window => 96.5% min heartbeat */
> +		wdd->min_hw_heartbeat_ms = 965 * heartbeat;
>   		break;
>   
>   	case RTIWWDSIZE_3P125:
> -		/* 3.125% open window => 96.9% min heartbeat */
> -		wdd->min_hw_heartbeat_ms = 969 * heartbeat;
> +		/* 3.125% open window => 97.9% min heartbeat */
> +		wdd->min_hw_heartbeat_ms = 979 * heartbeat;
>   		break;
>   
>   	default:
>
> base-commit: 860bbe8e618fd62446309e286ab4a83d38201c0a


Tested-by: Rafael Beims <rafael.beims@...adex.com>


Rafael