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

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Date: Thu, 4 Apr 2024 10:33:19 -0500
From: Judith Mendez <jm@...com>
To: 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: [PATCH v2] watchdog: rti_wdt: Set min_hw_heartbeat_ms to accommodate 5% safety margin

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
-- 
2.43.2