[PATCH 1/3] watchdog: digicolor: Avoid division by zero

[Tzung-Bi Shih <tzungbi@kernel.org>]

clk_get_rate() could return 0.  Avoid a division by zero panic.

Since get_timeleft() cannot propagate errors, check the clock rate early
in probe() and cache the rate in the driver data as it is unlikely to
change at runtime.

Fixes: 336694a01dae ("watchdog: digicolor: driver for Conexant Digicolor CX92755 SoC")
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
---
 drivers/watchdog/digicolor_wdt.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/watchdog/digicolor_wdt.c b/drivers/watchdog/digicolor_wdt.c
index 073d37867f47..de1a3267a972 100644
--- a/drivers/watchdog/digicolor_wdt.c
+++ b/drivers/watchdog/digicolor_wdt.c
@@ -25,6 +25,7 @@ struct dc_wdt {
 	void __iomem		*base;
 	struct clk		*clk;
 	spinlock_t		lock;
+	unsigned long		rate;
 };
 
 static unsigned timeout;
@@ -61,7 +62,7 @@ static int dc_wdt_start(struct watchdog_device *wdog)
 {
 	struct dc_wdt *wdt = watchdog_get_drvdata(wdog);
 
-	dc_wdt_set(wdt, wdog->timeout * clk_get_rate(wdt->clk));
+	dc_wdt_set(wdt, wdog->timeout * wdt->rate);
 
 	return 0;
 }
@@ -79,7 +80,7 @@ static int dc_wdt_set_timeout(struct watchdog_device *wdog, unsigned int t)
 {
 	struct dc_wdt *wdt = watchdog_get_drvdata(wdog);
 
-	dc_wdt_set(wdt, t * clk_get_rate(wdt->clk));
+	dc_wdt_set(wdt, t * wdt->rate);
 	wdog->timeout = t;
 
 	return 0;
@@ -90,7 +91,7 @@ static unsigned int dc_wdt_get_timeleft(struct watchdog_device *wdog)
 	struct dc_wdt *wdt = watchdog_get_drvdata(wdog);
 	uint32_t count = readl_relaxed(wdt->base + TIMER_A_COUNT);
 
-	return count / clk_get_rate(wdt->clk);
+	return count / wdt->rate;
 }
 
 static const struct watchdog_ops dc_wdt_ops = {
@@ -130,7 +131,11 @@ static int dc_wdt_probe(struct platform_device *pdev)
 	wdt->clk = devm_clk_get(dev, NULL);
 	if (IS_ERR(wdt->clk))
 		return PTR_ERR(wdt->clk);
-	dc_wdt_wdd.max_timeout = U32_MAX / clk_get_rate(wdt->clk);
+
+	wdt->rate = clk_get_rate(wdt->clk);
+	if (!wdt->rate)
+		return -EINVAL;
+	dc_wdt_wdd.max_timeout = U32_MAX / wdt->rate;
 	dc_wdt_wdd.timeout = dc_wdt_wdd.max_timeout;
 	dc_wdt_wdd.parent = dev;
 
-- 
2.53.0