linux-kernel - [PATCH 4.9 113/167] pwm: lp3943: Fix duty calculation in case period was clamped

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Date:   Mon, 13 Jun 2022 12:09:47 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Thierry Reding <thierry.reding@...il.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 113/167] pwm: lp3943: Fix duty calculation in case period was clamped

From: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>

[ Upstream commit 5e3b07ca5cc78cd4a987e78446849e41288d87cb ]

The hardware only supports periods <= 1.6 ms and if a bigger period is
requested it is clamped to 1.6 ms. In this case duty_cycle might be bigger
than 1.6 ms and then the duty cycle register is written with a value
bigger than LP3943_MAX_DUTY. So clamp duty_cycle accordingly.

Fixes: af66b3c0934e ("pwm: Add LP3943 PWM driver")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@...il.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/pwm/pwm-lp3943.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/pwm/pwm-lp3943.c b/drivers/pwm/pwm-lp3943.c
index 872ea76a4f19..4612315687cd 100644
--- a/drivers/pwm/pwm-lp3943.c
+++ b/drivers/pwm/pwm-lp3943.c
@@ -128,6 +128,7 @@ static int lp3943_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 	if (err)
 		return err;
 
+	duty_ns = min(duty_ns, period_ns);
 	val = (u8)(duty_ns * LP3943_MAX_DUTY / period_ns);
 
 	return lp3943_write_byte(lp3943, reg_duty, val);
-- 
2.35.1