linux-kernel - [PATCH v13 04/11] pwm: clps711x: Cast period to u32 before use as divisor

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Message-Id: <02ba64d8289bf84a8d140f5a3c38ed64a9474d3b.1587523702.git.gurus@codeaurora.org>
Date:   Tue, 21 Apr 2020 19:57:16 -0700
From:   Guru Das Srinagesh <gurus@...eaurora.org>
To:     linux-pwm@...r.kernel.org
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Subbaraman Narayanamurthy <subbaram@...eaurora.org>,
        David Collins <collinsd@...eaurora.org>,
        linux-kernel@...r.kernel.org,
        Guru Das Srinagesh <gurus@...eaurora.org>,
        Alexander Shiyan <shc_work@...l.ru>,
        Arnd Bergmann <arnd@...db.de>
Subject: [PATCH v13 04/11] pwm: clps711x: Cast period to u32 before use as divisor

Since the PWM framework is switching struct pwm_args.period's datatype
to u64, prepare for this transition by typecasting it to u32.

Also, since the dividend is still a 32-bit number, any divisor greater
than the numerator will cause the quotient to be zero, so return 0 in
that case to efficiently skip the division.

Cc: Alexander Shiyan <shc_work@...l.ru>
Cc: Arnd Bergmann <arnd@...db.de>

Signed-off-by: Guru Das Srinagesh <gurus@...eaurora.org>
---
 drivers/pwm/pwm-clps711x.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-clps711x.c b/drivers/pwm/pwm-clps711x.c
index 924d39a..0d368ac 100644
--- a/drivers/pwm/pwm-clps711x.c
+++ b/drivers/pwm/pwm-clps711x.c
@@ -43,7 +43,10 @@ static void clps711x_pwm_update_val(struct clps711x_chip *priv, u32 n, u32 v)
 static unsigned int clps711x_get_duty(struct pwm_device *pwm, unsigned int v)
 {
 	/* Duty cycle 0..15 max */
-	return DIV_ROUND_CLOSEST(v * 0xf, pwm->args.period);
+	if ((u32)pwm->args.period > (v * 0xf))
+		return 0;
+
+	return DIV_ROUND_CLOSEST(v * 0xf, (u32)pwm->args.period);
 }
 
 static int clps711x_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
-- 
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