linux-kernel - [PATCH v2 2/2] clocksource/drivers/timer-tegra186: fix watchdog self-pinging.

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Date: Sat, 17 Feb 2024 05:02:58 +0800
From: Pohsun Su <pohsuns@...dia.com>
To: <daniel.lezcano@...aro.org>, <tglx@...utronix.de>,
	<thierry.reding@...il.com>, <jonathanh@...dia.com>
CC: <sumitg@...dia.com>, <linux-kernel@...r.kernel.org>,
	<linux-tegra@...r.kernel.org>, Pohsun Su <pohsuns@...dia.com>
Subject: [PATCH v2 2/2] clocksource/drivers/timer-tegra186: fix watchdog self-pinging.

This change removes watchdog self-pinging behavior.

The timer irq handler is triggered due to the 1st expiration,
the handler disables and enables watchdog but also implicitly
clears the expiration count so the count can only be 0 or 1.

Since this watchdog supports opened, configured, or pinged by
systemd, We remove this behavior or the watchdog may not bark
when systemd crashes since the 5th expiration never comes.

Signed-off-by: Pohsun Su <pohsuns@...dia.com>
---
 drivers/clocksource/timer-tegra186.c | 27 ++-------------------------
 1 file changed, 2 insertions(+), 25 deletions(-)

diff --git a/drivers/clocksource/timer-tegra186.c b/drivers/clocksource/timer-tegra186.c
index 8f516366da86..acff97da138a 100644
--- a/drivers/clocksource/timer-tegra186.c
+++ b/drivers/clocksource/timer-tegra186.c
@@ -175,7 +175,8 @@ static void tegra186_wdt_enable(struct tegra186_wdt *wdt)
 		value |= WDTCR_PERIOD(1);
 
 		/* enable local interrupt for WDT petting */
-		value |= WDTCR_LOCAL_INT_ENABLE;
+		if (0)
+			value |= WDTCR_LOCAL_INT_ENABLE;
 
 		/* enable local FIQ and remote interrupt for debug dump */
 		if (0)
@@ -407,23 +408,10 @@ static int tegra186_timer_usec_init(struct tegra186_timer *tegra)
 	return clocksource_register_hz(&tegra->usec, USEC_PER_SEC);
 }
 
-static irqreturn_t tegra186_timer_irq(int irq, void *data)
-{
-	struct tegra186_timer *tegra = data;
-
-	if (watchdog_active(&tegra->wdt->base)) {
-		tegra186_wdt_disable(tegra->wdt);
-		tegra186_wdt_enable(tegra->wdt);
-	}
-
-	return IRQ_HANDLED;
-}
-
 static int tegra186_timer_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct tegra186_timer *tegra;
-	unsigned int irq;
 	int err;
 
 	tegra = devm_kzalloc(dev, sizeof(*tegra), GFP_KERNEL);
@@ -442,8 +430,6 @@ static int tegra186_timer_probe(struct platform_device *pdev)
 	if (err < 0)
 		return err;
 
-	irq = err;
-
 	/* create a watchdog using a preconfigured timer */
 	tegra->wdt = tegra186_wdt_create(tegra, 0);
 	if (IS_ERR(tegra->wdt)) {
@@ -470,17 +456,8 @@ static int tegra186_timer_probe(struct platform_device *pdev)
 		goto unregister_osc;
 	}
 
-	err = devm_request_irq(dev, irq, tegra186_timer_irq, 0,
-			       "tegra186-timer", tegra);
-	if (err < 0) {
-		dev_err(dev, "failed to request IRQ#%u: %d\n", irq, err);
-		goto unregister_usec;
-	}
-
 	return 0;
 
-unregister_usec:
-	clocksource_unregister(&tegra->usec);
 unregister_osc:
 	clocksource_unregister(&tegra->osc);
 unregister_tsc:
-- 
2.17.1