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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>,
	kernel test robot <lkp@intel.com>, Zong Li <zong.li@sifive.com>
Subject: [PATCH v14 4/5] pwm: sifive: Fix rounding issues in apply and get_state functions
Date: Fri,  9 May 2025 17:52:33 +0800	[thread overview]
Message-ID: <20250509095234.643890-5-nylon.chen@sifive.com> (raw)
In-Reply-To: <20250509095234.643890-1-nylon.chen@sifive.com>

Fix PWM apply and get_state rounding to ensure consistency between
setting and reading values

This fixes the reported errors:
pwm-sifive 10021000.pwm: .apply is supposed to round down
duty_cycle (requested: 360/504000, applied: 361/504124)
pwm-sifive 10021000.pwm: .apply is supposed to round down
period (requested: 504000, applied: 504124)

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202505080303.dBfU5YMS-lkp@intel.com/
Co-developed-by: Zong Li <zong.li@sifive.com>
Signed-off-by: Zong Li <zong.li@sifive.com>
Signed-off-by: Nylon Chen <nylon.chen@sifive.com>
---
 drivers/pwm/pwm-sifive.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
index 6259f8500f71..70cf644cde4a 100644
--- a/drivers/pwm/pwm-sifive.c
+++ b/drivers/pwm/pwm-sifive.c
@@ -122,8 +122,8 @@ static int pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 		state->enabled = false;
 
 	state->period = ddata->real_period;
-	state->duty_cycle =
-		(u64)duty * ddata->real_period >> PWM_SIFIVE_CMPWIDTH;
+	state->duty_cycle = DIV_ROUND_UP_ULL((u64)duty * ddata->real_period,
+					     (1U << PWM_SIFIVE_CMPWIDTH));
 	state->polarity = PWM_POLARITY_NORMAL;
 
 	return 0;
@@ -138,7 +138,8 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	unsigned long long num;
 	bool enabled;
 	int ret = 0;
-	u32 frac, inactive;
+	u64 frac;
+	u32 inactive;
 
 	if (state->polarity != PWM_POLARITY_NORMAL)
 		return -EINVAL;
@@ -157,9 +158,11 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	 * consecutively
 	 */
 	num = (u64)duty_cycle * (1U << PWM_SIFIVE_CMPWIDTH);
-	frac = DIV64_U64_ROUND_CLOSEST(num, state->period);
+	frac = num;
+	do_div(frac, state->period);
 	/* The hardware cannot generate a 0% duty cycle */
-	frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);
+	frac = min(frac, (u64)(1U << PWM_SIFIVE_CMPWIDTH) - 1);
+	/* pwmcmp register must be loaded with the inactive(invert the duty) */
 	inactive = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - frac;
 
 	mutex_lock(&ddata->lock);
-- 
2.34.1


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  parent reply	other threads:[~2025-05-09 10:36 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 ` [PATCH v14 2/5] pwm: sifive: change the PWM algorithm Nylon Chen
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 ` Nylon Chen [this message]
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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