linux-kernel - [PATCH] watchdog: stm32_iwdg: initialize default timeout

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Date: Wed, 28 Feb 2024 13:27:23 -0500
From: Ben Wolsieffer <ben.wolsieffer@...ring.com>
To: linux-kernel@...r.kernel.org,
	linux-watchdog@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org
Cc: Wim Van Sebroeck <wim@...ux-watchdog.org>,
	Guenter Roeck <linux@...ck-us.net>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Christophe Roullier <christophe.roullier@...com>,
	Ben Wolsieffer <ben.wolsieffer@...ring.com>
Subject: [PATCH] watchdog: stm32_iwdg: initialize default timeout

The driver never sets a default timeout value, therefore it is
initialized to zero. When CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED is
enabled, the watchdog is started during probe. The kernel is supposed to
automatically ping the watchdog from this point until userspace takes
over, but this does not happen if the configured timeout is zero. A zero
timeout causes watchdog_need_worker() to return false, so the heartbeat
worker does not run and the system therefore resets soon after the
driver is probed.

This patch fixes this by setting an arbitrary non-zero default timeout.
The default could be read from the hardware instead, but I didn't see
any reason to add this complexity.

This has been tested on an STM32F746.

Fixes: 85fdc63fe256 ("drivers: watchdog: stm32_iwdg: set WDOG_HW_RUNNING at probe")
Signed-off-by: Ben Wolsieffer <ben.wolsieffer@...ring.com>
---
 drivers/watchdog/stm32_iwdg.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/watchdog/stm32_iwdg.c b/drivers/watchdog/stm32_iwdg.c
index d9fd50df9802..5404e0387620 100644
--- a/drivers/watchdog/stm32_iwdg.c
+++ b/drivers/watchdog/stm32_iwdg.c
@@ -20,6 +20,8 @@
 #include <linux/platform_device.h>
 #include <linux/watchdog.h>

+#define DEFAULT_TIMEOUT 10
+
 /* IWDG registers */
 #define IWDG_KR		0x00 /* Key register */
 #define IWDG_PR		0x04 /* Prescaler Register */
@@ -248,6 +250,7 @@ static int stm32_iwdg_probe(struct platform_device *pdev)
 	wdd->parent = dev;
 	wdd->info = &stm32_iwdg_info;
 	wdd->ops = &stm32_iwdg_ops;
+	wdd->timeout = DEFAULT_TIMEOUT;
 	wdd->min_timeout = DIV_ROUND_UP((RLR_MIN + 1) * PR_MIN, wdt->rate);
 	wdd->max_hw_heartbeat_ms = ((RLR_MAX + 1) * wdt->data->max_prescaler *
 				    1000) / wdt->rate;
-- 
2.43.0