[PATCH 1/2] pwm: lp3943: fix duty calculation in case period was clamped

[PATCH 1/2] pwm: lp3943: fix duty calculation in case period was clamped

[Uwe Kleine-König]

The hardware only supports periods <= 1.6 ms and if a bigger period is
requested it is clamped to 1.6 ms. In this case duty_cycle might be bigger
than 1.6 ms and then the duty cycle register is written with a value
bigger than LP3943_MAX_DUTY. So clamp duty_cycle accordingly.

Fixes: af66b3c0934e ("pwm: Add LP3943 PWM driver")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
 drivers/pwm/pwm-lp3943.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/pwm/pwm-lp3943.c b/drivers/pwm/pwm-lp3943.c
index ea17d446a627..2bd04ecb508c 100644
--- a/drivers/pwm/pwm-lp3943.c
+++ b/drivers/pwm/pwm-lp3943.c
@@ -125,6 +125,7 @@ static int lp3943_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 	if (err)
 		return err;
 
+	duty_ns = min(duty_ns, period_ns);
 	val = (u8)(duty_ns * LP3943_MAX_DUTY / period_ns);
 
 	return lp3943_write_byte(lp3943, reg_duty, val);

base-commit: 3123109284176b1532874591f7c81f3837bbdc17
-- 
2.35.1

[PATCH 2/2] pwm: lp3943: Implement .apply() callback

[Uwe Kleine-König]

To eventually get rid of all legacy drivers convert this driver to the
modern world implementing .apply().

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
 drivers/pwm/pwm-lp3943.c | 41 +++++++++++++++++++++++++++++++++-------
 1 file changed, 34 insertions(+), 7 deletions(-)

diff --git a/drivers/pwm/pwm-lp3943.c b/drivers/pwm/pwm-lp3943.c
index 2bd04ecb508c..215ef9069114 100644
--- a/drivers/pwm/pwm-lp3943.c
+++ b/drivers/pwm/pwm-lp3943.c
@@ -93,7 +93,7 @@ static void lp3943_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
 }
 
 static int lp3943_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
-			     int duty_ns, int period_ns)
+			     u64 duty_ns, u64 period_ns)
 {
 	struct lp3943_pwm *lp3943_pwm = to_lp3943_pwm(chip);
 	struct lp3943 *lp3943 = lp3943_pwm->lp3943;
@@ -118,15 +118,20 @@ static int lp3943_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 		reg_duty     = LP3943_REG_PWM1;
 	}
 
-	period_ns = clamp(period_ns, LP3943_MIN_PERIOD, LP3943_MAX_PERIOD);
-	val       = (u8)(period_ns / LP3943_MIN_PERIOD - 1);
+	/*
+	 * Note that after this clamping, period_ns fits into an int. This is
+	 * helpful because we can resort to integer division below instead of
+	 * the (more expensive) 64 bit division.
+	 */
+	period_ns = clamp(period_ns, (u64)LP3943_MIN_PERIOD, (u64)LP3943_MAX_PERIOD);
+	val       = (u8)((int)period_ns / LP3943_MIN_PERIOD - 1);
 
 	err = lp3943_write_byte(lp3943, reg_prescale, val);
 	if (err)
 		return err;
 
 	duty_ns = min(duty_ns, period_ns);
-	val = (u8)(duty_ns * LP3943_MAX_DUTY / period_ns);
+	val = (u8)((int)duty_ns * LP3943_MAX_DUTY / (int)period_ns);
 
 	return lp3943_write_byte(lp3943, reg_duty, val);
 }
@@ -183,12 +188,34 @@ static void lp3943_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 	lp3943_pwm_set_mode(lp3943_pwm, pwm_map, LP3943_GPIO_OUT_HIGH);
 }
 
+static int lp3943_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			    const struct pwm_state *state)
+{
+	int err;
+
+	if (state->polarity != PWM_POLARITY_NORMAL)
+		return -EINVAL;
+
+	if (!state->enabled) {
+		if (pwm->state.enabled)
+			lp3943_pwm_disable(chip, pwm);
+		return 0;
+	}
+
+	err = lp3943_pwm_config(chip, pwm, state->duty_cycle, state->period);
+	if (err)
+		return err;
+
+	if (!pwm->state.enabled)
+		err = lp3943_pwm_enable(chip, pwm);
+
+	return err;
+}
+
 static const struct pwm_ops lp3943_pwm_ops = {
 	.request	= lp3943_pwm_request,
 	.free		= lp3943_pwm_free,
-	.config		= lp3943_pwm_config,
-	.enable		= lp3943_pwm_enable,
-	.disable	= lp3943_pwm_disable,
+	.apply		= lp3943_pwm_apply,
 	.owner		= THIS_MODULE,
 };
 
-- 
2.35.1

Re: [PATCH 1/2] pwm: lp3943: fix duty calculation in case period was clamped

[Thierry Reding]

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On Fri, Apr 08, 2022 at 05:22:38PM +0200, Uwe Kleine-König wrote:
> The hardware only supports periods <= 1.6 ms and if a bigger period is
> requested it is clamped to 1.6 ms. In this case duty_cycle might be bigger
> than 1.6 ms and then the duty cycle register is written with a value
> bigger than LP3943_MAX_DUTY. So clamp duty_cycle accordingly.
> 
> Fixes: af66b3c0934e ("pwm: Add LP3943 PWM driver")
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> ---
>  drivers/pwm/pwm-lp3943.c | 1 +
>  1 file changed, 1 insertion(+)

Both patches applied, thanks.

Thierry

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