Re: [PATCH] watchdog: rti_wdt: Set min_hw_heartbeat_ms to accommodate 5% safety margin

Rafael Beims
2024-04-05T12:38:03Z

On 03/04/2024 18:24, 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.
>
> Signed-off-by: Judith Mendez <jm@ti.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:

I tested this patch by enabling the systemd watchdog adding
RuntimeWatchdogSec=30 to system.conf on a Verdin AM62.

This setup causes watchdog resets without the patch, and with the patch
applied I didn't see any watchdog related reboots.

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

Rafael