linux-kernel - [PATCH v10 2/3] pwm: sifive: change the PWM algorithm

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Message-Id: <20241224093902.1632627-3-nylon.chen@sifive.com>
Date: Tue, 24 Dec 2024 17:39:00 +0800
From: Nylon Chen <nylon.chen@...ive.com>
To: linux-kernel@...r.kernel.org,
	linux-pwm@...r.kernel.org,
	devicetree@...r.kernel.org
Cc: Nylon Chen <nylon.chen@...ive.com>,
	Zong Li <zong.li@...ive.com>,
	Vincent Chen <vincent.chen@...ive.com>,
	Uwe Kleine-König <ukleinek@...nel.org>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Samuel Holland <samuel.holland@...ive.com>,
	linux-riscv@...ts.infradead.org
Subject: [PATCH v10 2/3] pwm: sifive: change the PWM 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]

Co-developed-by: Zong Li <zong.li@...ive.com>
Signed-off-by: Zong Li <zong.li@...ive.com>
Co-developed-by: Vincent Chen <vincent.chen@...ive.com>
Signed-off-by: Vincent Chen <vincent.chen@...ive.com>
Signed-off-by: Nylon Chen <nylon.chen@...ive.com>
---
 drivers/pwm/pwm-sifive.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
index d5b647e6be78..bb9146267bc5 100644
--- a/drivers/pwm/pwm-sifive.c
+++ b/drivers/pwm/pwm-sifive.c
@@ -110,9 +110,10 @@ static int pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 				struct pwm_state *state)
 {
 	struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
-	u32 duty, val;
+	u32 duty, val, inactive;
 
-	duty = readl(ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
+	inactive = readl(ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
+	duty = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - inactive;
 
 	state->enabled = duty > 0;
 
@@ -123,7 +124,7 @@ static int pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 	state->period = ddata->real_period;
 	state->duty_cycle =
 		(u64)duty * ddata->real_period >> PWM_SIFIVE_CMPWIDTH;
-	state->polarity = PWM_POLARITY_INVERSED;
+	state->polarity = PWM_POLARITY_NORMAL;
 
 	return 0;
 }
@@ -137,9 +138,9 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	unsigned long long num;
 	bool enabled;
 	int ret = 0;
-	u32 frac;
+	u32 frac, inactive;
 
-	if (state->polarity != PWM_POLARITY_INVERSED)
+	if (state->polarity != PWM_POLARITY_NORMAL)
 		return -EINVAL;
 
 	cur_state = pwm->state;
@@ -157,8 +158,9 @@ 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 */
+	/* The hardware cannot generate a 0% duty cycle */
 	frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);
+	inactive = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - frac;
 
 	mutex_lock(&ddata->lock);
 	if (state->period != ddata->approx_period) {
@@ -190,7 +192,7 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 		}
 	}
 
-	writel(frac, ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
+	writel(inactive, ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
 
 	if (!state->enabled)
 		clk_disable(ddata->clk);
-- 
2.34.1