linux-kernel - [PATCH v9 3/3] pwm: sifive: Fix the error in the idempotent test within the pwm_apply_state

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Date: Thu, 22 Feb 2024 16:12:31 +0800
From: Nylon Chen <nylon.chen@...ive.com>
To: linux-riscv@...ts.infradead.org,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-pwm@...r.kernel.org,
	conor@...nel.org,
	robh+dt@...nel.org,
	krzysztof.kozlowski+dt@...aro.org,
	palmer@...belt.com,
	paul.walmsley@...ive.com,
	aou@...s.berkeley.edu,
	thierry.reding@...il.com,
	u.kleine-koenig@...gutronix.de
Cc: vincent.chen@...ive.com,
	zong.li@...ive.com,
	nylon.chen@...ive.com,
	nylon7717@...il.com
Subject: [PATCH v9 3/3] pwm: sifive: Fix the error in the idempotent test within the pwm_apply_state_debug function

Round the result to the nearest whole number. This ensures that
real_period is always a reasonable integer that is not lower than the
actual value.

e.g.
$ echo 110 > /sys/devices/platform/led-controller-1/leds/d12/brightness
$ .apply is not idempotent (ena=1 pol=0 1739692/4032985) -> (ena=1 pol=0 1739630/4032985)

Co-developed-by: Zong Li <zong.li@...ive.com>
Signed-off-by: Zong Li <zong.li@...ive.com>
Signed-off-by: Nylon Chen <nylon.chen@...ive.com>
---
 drivers/pwm/pwm-sifive.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
index a586cfe4191b..bebcbebacccd 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);
 }
-- 
2.43.0