Thread (14 messages) 14 messages, 3 authors, 2021-01-13

Re: [PATCH 1/5] gpio: mvebu: fix pwm get_state period calculation

From: Uwe Kleine-König <hidden>
Date: 2021-01-11 20:18:30
Also in: linux-arm-kernel, linux-pwm

Hello Baruch,

$Subject ~= s/get_state/.get_state/ ?

On Mon, Jan 11, 2021 at 01:17:02PM +0200, Baruch Siach wrote:
quoted hunk ↗ jump to hunk
The period is the sum of on and off values.

Reported-by: Russell King <linux@armlinux.org.uk>
Fixes: 757642f9a584e ("gpio: mvebu: Add limited PWM support")
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
---
 drivers/gpio/gpio-mvebu.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)
diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c
index 672681a976f5..a912a8fed197 100644
--- a/drivers/gpio/gpio-mvebu.c
+++ b/drivers/gpio/gpio-mvebu.c
@@ -676,20 +676,17 @@ static void mvebu_pwm_get_state(struct pwm_chip *chip,
 	else
 		state->duty_cycle = 1;
 
+	val = (unsigned long long) u; /* on duration */
 	regmap_read(mvpwm->regs, mvebu_pwmreg_blink_off_duration(mvpwm), &u);
-	val = (unsigned long long) u * NSEC_PER_SEC;
+	val += (unsigned long long) u; /* period = on + off duration */
+	val *= NSEC_PER_SEC;
 	do_div(val, mvpwm->clk_rate);
-	if (val < state->duty_cycle) {
+	if (val > UINT_MAX)
+		state->period = UINT_MAX;
+	else if (val)
+		state->period = val;
+	else
 		state->period = 1;
-	} else {
-		val -= state->duty_cycle;
-		if (val > UINT_MAX)
-			state->period = UINT_MAX;
-		else if (val)
-			state->period = val;
-		else
-			state->period = 1;
-	}
The patch looks good, the patch description could be a bit more verbose.
Something like:

	Calculate the period as

		($on + $off) / clkrate

	instead of

		$off / clkrate - $on / clkrate

	.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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