linux-kernel - [PATCH 2/3] pwm-sun4i: calculate "delay_jiffies" directly, eliminate absolute time

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Date:   Tue, 25 Jan 2022 13:34:28 +0100
From:   Max Kellermann <max.kellermann@...il.com>
To:     linux-pwm@...r.kernel.org, thierry.reding@...il.com,
        u.kleine-koenig@...gutronix.de, lee.jones@...aro.org
Cc:     linux-kernel@...r.kernel.org, andrey@...edev.lt,
        Max Kellermann <max.kellermann@...il.com>,
        stable@...r.kernel.org
Subject: [PATCH 2/3] pwm-sun4i: calculate "delay_jiffies" directly, eliminate absolute time

Basically this code did "jiffies + period - jiffies", and we can
simply eliminate the "jiffies" time stamp here.

Cc: stable@...r.kernel.org
Signed-off-by: Max Kellermann <max.kellermann@...il.com>
---
 drivers/pwm/pwm-sun4i.c | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
index c7c564a6bf36..b44deececb8b 100644
--- a/drivers/pwm/pwm-sun4i.c
+++ b/drivers/pwm/pwm-sun4i.c
@@ -234,9 +234,8 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	struct pwm_state cstate;
 	u32 ctrl, duty = 0, period = 0, val;
 	int ret;
+	unsigned int delay_jiffies;
 	unsigned int delay_us, prescaler = 0;
-	unsigned long now;
-	unsigned long next_period;
 	bool bypass;
 
 	pwm_get_state(pwm, &cstate);
@@ -284,8 +283,6 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 
 	val = (duty & PWM_DTY_MASK) | PWM_PRD(period);
 	sun4i_pwm_writel(sun4i_pwm, val, PWM_CH_PRD(pwm->hwpwm));
-	next_period = jiffies +
-		nsecs_to_jiffies(cstate.period + 1000);
 
 	if (state->polarity != PWM_POLARITY_NORMAL)
 		ctrl &= ~BIT_CH(PWM_ACT_STATE, pwm->hwpwm);
@@ -305,14 +302,12 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 		return 0;
 
 	/* We need a full period to elapse before disabling the channel. */
-	now = jiffies;
-	if (time_before(now, next_period)) {
-		delay_us = jiffies_to_usecs(next_period - now);
-		if ((delay_us / 500) > MAX_UDELAY_MS)
-			msleep(delay_us / 1000 + 1);
-		else
-			usleep_range(delay_us, delay_us * 2);
-	}
+	delay_jiffies = nsecs_to_jiffies(cstate.period + 1000);
+	delay_us = jiffies_to_usecs(delay_jiffies);
+	if ((delay_us / 500) > MAX_UDELAY_MS)
+		msleep(delay_us / 1000 + 1);
+	else
+		usleep_range(delay_us, delay_us * 2);
 
 	spin_lock(&sun4i_pwm->ctrl_lock);
 	ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
-- 
2.34.0