linux-kernel - [PATCH 2/2] pwm: sifive: change the PWM controlled LED algorithm

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Date:   Fri, 13 Jan 2023 16:31:15 +0800
From:   Nylon Chen <nylon.chen@...ive.com>
To:     paul.walmsley@...ive.com, palmer@...belt.com,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Cc:     nylon7717@...il.com, zong.li@...ive.com, greentime.hu@...ive.com,
        vincent.chen@...ive.com, Nylon Chen <nylon.chen@...ive.com>
Subject: [PATCH 2/2] pwm: sifive: change the PWM controlled LED algorithm

The `frac` variable represents the pulse inactive time, and the result of
this algorithm is the pulse active time. Therefore, we must reverse the
result.

Signed-off-by: Nylon Chen <nylon.chen@...ive.com>
Reviewed-by: Vincent Chen <vincent.chen@...ive.com>
---
 drivers/pwm/pwm-sifive.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
index 62b6acc6373d..a5eda165d071 100644
--- a/drivers/pwm/pwm-sifive.c
+++ b/drivers/pwm/pwm-sifive.c
@@ -158,6 +158,7 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	frac = DIV64_U64_ROUND_CLOSEST(num, state->period);
 	/* The hardware cannot generate a 100% duty cycle */
 	frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);
+	frac = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - frac;
 
 	mutex_lock(&ddata->lock);
 	if (state->period != ddata->approx_period) {
-- 
2.36.1