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

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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@xxxxxx>
---
  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@xxxxxxxxxxx>


Rafael






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