linux-kernel - [PATCH AUTOSEL 5.7 317/388] pwm: imx27: Fix rounding behavior

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Message-Id: <20200618010805.600873-317-sashal@kernel.org>
Date:   Wed, 17 Jun 2020 21:06:54 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Thierry Reding <thierry.reding@...il.com>,
        Sasha Levin <sashal@...nel.org>, linux-pwm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH AUTOSEL 5.7 317/388] pwm: imx27: Fix rounding behavior

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

[ Upstream commit aef1a3799b5cb3ba4841f6034497b179646ccc70 ]

To not trigger the warnings provided by CONFIG_PWM_DEBUG

 - use up-rounding in .get_state()
 - don't divide by the result of a division
 - don't use the rounded counter value for the period length to calculate
   the counter value for the duty cycle

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-imx27.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/pwm/pwm-imx27.c b/drivers/pwm/pwm-imx27.c
index a6e40d4c485f..732a6f3701e8 100644
--- a/drivers/pwm/pwm-imx27.c
+++ b/drivers/pwm/pwm-imx27.c
@@ -150,13 +150,12 @@ static void pwm_imx27_get_state(struct pwm_chip *chip,
 
 	prescaler = MX3_PWMCR_PRESCALER_GET(val);
 	pwm_clk = clk_get_rate(imx->clk_per);
-	pwm_clk = DIV_ROUND_CLOSEST_ULL(pwm_clk, prescaler);
 	val = readl(imx->mmio_base + MX3_PWMPR);
 	period = val >= MX3_PWMPR_MAX ? MX3_PWMPR_MAX : val;
 
 	/* PWMOUT (Hz) = PWMCLK / (PWMPR + 2) */
-	tmp = NSEC_PER_SEC * (u64)(period + 2);
-	state->period = DIV_ROUND_CLOSEST_ULL(tmp, pwm_clk);
+	tmp = NSEC_PER_SEC * (u64)(period + 2) * prescaler;
+	state->period = DIV_ROUND_UP_ULL(tmp, pwm_clk);
 
 	/*
 	 * PWMSAR can be read only if PWM is enabled. If the PWM is disabled,
@@ -167,8 +166,8 @@ static void pwm_imx27_get_state(struct pwm_chip *chip,
 	else
 		val = imx->duty_cycle;
 
-	tmp = NSEC_PER_SEC * (u64)(val);
-	state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, pwm_clk);
+	tmp = NSEC_PER_SEC * (u64)(val) * prescaler;
+	state->duty_cycle = DIV_ROUND_UP_ULL(tmp, pwm_clk);
 
 	pwm_imx27_clk_disable_unprepare(imx);
 }
@@ -220,22 +219,23 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip);
 	struct pwm_state cstate;
 	unsigned long long c;
+	unsigned long long clkrate;
 	int ret;
 	u32 cr;
 
 	pwm_get_state(pwm, &cstate);
 
-	c = clk_get_rate(imx->clk_per);
-	c *= state->period;
+	clkrate = clk_get_rate(imx->clk_per);
+	c = clkrate * state->period;
 
-	do_div(c, 1000000000);
+	do_div(c, NSEC_PER_SEC);
 	period_cycles = c;
 
 	prescale = period_cycles / 0x10000 + 1;
 
 	period_cycles /= prescale;
-	c = (unsigned long long)period_cycles * state->duty_cycle;
-	do_div(c, state->period);
+	c = clkrate * state->duty_cycle;
+	do_div(c, NSEC_PER_SEC * prescale);
 	duty_cycles = c;
 
 	/*
-- 
2.25.1