[PATCH] watchdog: airoha: Prevent division by zero when clock frequency is zero

[Wayen Yan]

clk_get_rate() can return 0 when the clock provider is not properly
configured or the clock is unmanaged. The driver uses wdt_freq as a
divisor directly in airoha_wdt_probe() to compute max_timeout and in
airoha_wdt_get_timeleft() to compute the remaining time, which results
in a division by zero.

Add a check for wdt_freq == 0 in probe and return -EINVAL with
dev_err_probe() to prevent the division by zero and provide a
diagnostic message.

Fixes: 3cf67f3769b8 ("watchdog: Add support for Airoha EN7851 watchdog")
Signed-off-by: Wayen Yan <win847@xxxxxxxxx>
---
 drivers/watchdog/airoha_wdt.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/watchdog/airoha_wdt.c b/drivers/watchdog/airoha_wdt.c
index dc8ca11c14d8..4bd333189b87 100644
--- a/drivers/watchdog/airoha_wdt.c
+++ b/drivers/watchdog/airoha_wdt.c
@@ -147,6 +147,9 @@ static int airoha_wdt_probe(struct platform_device *pdev)
 
 	/* Watchdog ticks at half the bus rate */
 	airoha_wdt->wdt_freq = clk_get_rate(bus_clk) / 2;
+	if (!airoha_wdt->wdt_freq)
+		return dev_err_probe(dev, -EINVAL,
+				     "invalid clock frequency\n");
 
 	/* Initialize struct watchdog device */
 	wdog_dev = &airoha_wdt->wdog_dev;
-- 
2.51.0