linux-kernel - [PATCH v2 2/5] watchdog: s3c2410_wdt: Fix max

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Message-Id: <20250514094220.1561378-3-sw617.shin@samsung.com>
Date: Wed, 14 May 2025 18:42:17 +0900
From: Sangwook Shin <sw617.shin@...sung.com>
To: krzk@...nel.org, alim.akhtar@...sung.com, wim@...ux-watchdog.org,
	linux@...ck-us.net
Cc: linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org,
	linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org, Sangwook Shin
	<sw617.shin@...sung.com>, Kyunghwan Seo <khwan.seo@...sung.com>
Subject: [PATCH v2 2/5] watchdog: s3c2410_wdt: Fix max_timeout being
 calculated larger

Fix the issue of max_timeout being calculated larger than actual value.
The calculation result of freq / (S3C2410_WTCON_PRESCALE_MAX + 1) /
S3C2410_WTCON_MAXDIV is smaller than the actual value because the remainder
is discarded during the calculation process. This leads to a larger
calculated value for max_timeout compared to the actual settable value.
A ceiling operation is applied in the calculation process to resolve this.

Signed-off-by: Sangwook Shin <sw617.shin@...sung.com>
Signed-off-by: Kyunghwan Seo <khwan.seo@...sung.com>
---
 drivers/watchdog/s3c2410_wdt.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c
index 228f86d83663..c6166d927155 100644
--- a/drivers/watchdog/s3c2410_wdt.c
+++ b/drivers/watchdog/s3c2410_wdt.c
@@ -379,8 +379,8 @@ static inline unsigned int s3c2410wdt_max_timeout(struct s3c2410_wdt *wdt)
 {
 	const unsigned long freq = s3c2410wdt_get_freq(wdt);
 
-	return S3C2410_WTCNT_MAXCNT / (freq / (S3C2410_WTCON_PRESCALE_MAX + 1)
-				       / S3C2410_WTCON_MAXDIV);
+	return S3C2410_WTCNT_MAXCNT / DIV_ROUND_UP(freq,
+		(S3C2410_WTCON_PRESCALE_MAX + 1) * S3C2410_WTCON_MAXDIV);
 }
 
 static int s3c2410wdt_disable_wdt_reset(struct s3c2410_wdt *wdt, bool mask)
-- 
2.40.1