linux-kernel - [v5 2/2] pwm: sifive: change the PWM controlled LED algorithm

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Message-ID: <20231024101902.6689-3-nylon.chen@sifive.com>
Date:   Tue, 24 Oct 2023 18:19:02 +0800
From:   Nylon Chen <nylon.chen@...ive.com>
To:     linux-pwm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, thierry.reding@...il.com,
        u.kleine-koenig@...gutronix.de, emil.renner.berthing@...onical.com,
        vincent.chen@...ive.com
Cc:     nylon.chen@...ive.com, greentime.hu@...ive.com, zong.li@...ive.com,
        nylon7717@...il.com
Subject: [v5 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.

The reference is SiFive FU740-C000 Manual[0]

Link: https://sifive.cdn.prismic.io/sifive/1a82e600-1f93-4f41-b2d8-86ed8b16acba_fu740-c000-manual-v1p6.pdf [0]

Signed-off-by: Nylon Chen <nylon.chen@...ive.com>
Signed-off-by: Vincent Chen <vincent.chen@...ive.com>
---
 drivers/pwm/pwm-sifive.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
index eabddb7c7820..353c2342fbf1 100644
--- a/drivers/pwm/pwm-sifive.c
+++ b/drivers/pwm/pwm-sifive.c
@@ -101,7 +101,7 @@ static void pwm_sifive_update_clock(struct pwm_sifive_ddata *ddata,
 
 	/* As scale <= 15 the shift operation cannot overflow. */
 	num = (unsigned long long)NSEC_PER_SEC << (PWM_SIFIVE_CMPWIDTH + scale);
-	ddata->real_period = div64_ul(num, rate);
+	ddata->real_period = DIV_ROUND_UP_ULL(num, rate);
 	dev_dbg(ddata->chip.dev,
 		"New real_period = %u ns\n", ddata->real_period);
 }
@@ -121,13 +121,14 @@ static int pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 		state->enabled = false;
 
 	state->period = ddata->real_period;
+
+	duty = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - duty;
 	state->duty_cycle =
 		(u64)duty * ddata->real_period >> PWM_SIFIVE_CMPWIDTH;
-	state->polarity = PWM_POLARITY_INVERSED;
+	state->polarity = PWM_POLARITY_NORMAL;
 
 	return 0;
 }
-
 static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 			    const struct pwm_state *state)
 {
@@ -139,7 +140,7 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	int ret = 0;
 	u32 frac;
 
-	if (state->polarity != PWM_POLARITY_INVERSED)
+	if (state->polarity != PWM_POLARITY_NORMAL)
 		return -EINVAL;
 
 	cur_state = pwm->state;
@@ -158,6 +159,7 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	num = (u64)duty_cycle * (1U << PWM_SIFIVE_CMPWIDTH);
 	frac = DIV64_U64_ROUND_CLOSEST(num, state->period);
 	/* The hardware cannot generate a 100% duty cycle */
+	frac = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - frac;
 	frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);
 
 	mutex_lock(&ddata->lock);
-- 
2.42.0