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From: Nylon Chen <nylon.chen@sifive.com>
To: "Uwe Kleine-König" <ukleinek@kernel.org>,
	devicetree@vger.kernel.org, linux-pwm@vger.kernel.org,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Cc: conor@kernel.org, robh@kernel.org, krzk+dt@kernel.org,
	paul.walmsley@sifive.com, palmer@dabbelt.com,
	aou@eecs.berkeley.edu, samuel.holland@sifive.com,
	Nylon Chen <nylon.chen@sifive.com>, Zong Li <zong.li@sifive.com>,
	Vincent Chen <vincent.chen@sifive.com>
Subject: [PATCH v14 2/5] pwm: sifive: change the PWM algorithm
Date: Fri,  9 May 2025 17:52:31 +0800	[thread overview]
Message-ID: <20250509095234.643890-3-nylon.chen@sifive.com> (raw)
In-Reply-To: <20250509095234.643890-1-nylon.chen@sifive.com>

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@sifive.com>
Signed-off-by: Zong Li <zong.li@sifive.com>
Co-developed-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Nylon Chen <nylon.chen@sifive.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


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  parent reply	other threads:[~2025-05-09 10:37 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-05-09  9:52 [PATCH v14 0/5] Change PWM-controlled LED pin active mode and algorithm Nylon Chen
2025-05-09  9:52 ` [PATCH v14 1/5] riscv: dts: sifive: unleashed/unmatched: Remove PWM controlled LED's active-low properties Nylon Chen
2025-05-09  9:52 ` Nylon Chen [this message]
2025-05-09  9:52 ` [PATCH v14 3/5] pwm: sifive: Fix the error in the idempotent test within the pwm_apply_state_debug function Nylon Chen
2025-05-09  9:52 ` [PATCH v14 4/5] pwm: sifive: Fix rounding issues in apply and get_state functions Nylon Chen
2025-05-09  9:52 ` [PATCH v14 5/5] pwm: sifive: clarify inverted compare logic in comments Nylon Chen
2025-05-28 10:21 ` [PATCH v14 0/5] Change PWM-controlled LED pin active mode and algorithm Uwe Kleine-König
2025-05-28 11:25   ` Conor Dooley

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