[PATCH v7 1/9] pwm: rzg2l-gpt: Fix macro used for period/duty cycle conversion

[Biju]

From: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>

The driver converts state->period and state->duty_cycle (both in
nanoseconds) into timer ticks by multiplying with rate_khz and
dividing by USEC_PER_SEC. Since rate_khz is expressed in kHz
(cycles per millisecond), the correct divisor is NSEC_PER_MSEC,
not USEC_PER_SEC. Both constants evaluate to 1000000, so this is
a readability/correctness fix with no functional change, and it
keeps the calculation's units self-consistent with the comment
describing the overflow bound.

Update rzg2l_gpt_calculate_period_or_duty() and rzg2l_gpt_config()
accordingly.

Cc: stable@xxxxxxxxxx
Fixes: 061f087f5d0b ("pwm: Add support for RZ/G2L GPT")
Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
---
v7:
 * New patch.
---
 drivers/pwm/pwm-rzg2l-gpt.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/pwm/pwm-rzg2l-gpt.c b/drivers/pwm/pwm-rzg2l-gpt.c
index 1569f3ba8c53..108fa99f832d 100644
--- a/drivers/pwm/pwm-rzg2l-gpt.c
+++ b/drivers/pwm/pwm-rzg2l-gpt.c
@@ -208,13 +208,13 @@ static u64 rzg2l_gpt_calculate_period_or_duty(struct rzg2l_gpt_chip *rzg2l_gpt,
 
 	/*
 	 * The calculation doesn't overflow an u64 because prescale ≤ 5 and so
-	 * tmp = val << (2 * prescale) * USEC_PER_SEC
+	 * tmp = val << (2 * prescale) * NSEC_PER_MSEC
 	 *     < 2^32 * 2^10 * 10^6
 	 *     < 2^32 * 2^10 * 2^20
 	 *     = 2^62
 	 */
 	tmp = (u64)val << (2 * prescale);
-	tmp *= USEC_PER_SEC;
+	tmp *= NSEC_PER_MSEC;
 
 	return DIV64_U64_ROUND_UP(tmp, rzg2l_gpt->rate_khz);
 }
@@ -266,7 +266,7 @@ static int rzg2l_gpt_config(struct pwm_chip *chip, struct pwm_device *pwm,
 	u8 prescale;
 
 	/* Limit period/duty cycle to max value supported by the HW */
-	period_ticks = mul_u64_u64_div_u64(state->period, rzg2l_gpt->rate_khz, USEC_PER_SEC);
+	period_ticks = mul_u64_u64_div_u64(state->period, rzg2l_gpt->rate_khz, NSEC_PER_MSEC);
 	if (period_ticks > RZG2L_MAX_TICKS)
 		period_ticks = RZG2L_MAX_TICKS;
 	/*
@@ -288,7 +288,7 @@ static int rzg2l_gpt_config(struct pwm_chip *chip, struct pwm_device *pwm,
 	prescale = rzg2l_gpt_calculate_prescale(period_ticks);
 	pv = rzg2l_gpt_calculate_pv_or_dc(period_ticks, prescale);
 
-	duty_ticks = mul_u64_u64_div_u64(state->duty_cycle, rzg2l_gpt->rate_khz, USEC_PER_SEC);
+	duty_ticks = mul_u64_u64_div_u64(state->duty_cycle, rzg2l_gpt->rate_khz, NSEC_PER_MSEC);
 	if (duty_ticks > period_ticks)
 		duty_ticks = period_ticks;
 	dc = rzg2l_gpt_calculate_pv_or_dc(duty_ticks, prescale);
-- 
2.43.0