pwm: Let pwm_set_waveform() succeed even if lowlevel driver rounded up

Waveform parameters are supposed to be rounded down to the next value
possible for the hardware. However when a requested value is too small,
.round_waveform_tohw() is supposed to pick the next bigger value and
return 1. Let pwm_set_waveform() behave in the same way.

This creates consistency between pwm_set_waveform_might_sleep() with
exact=false and pwm_round_waveform_might_sleep() +
pwm_set_waveform_might_sleep() with exact=true.

The PWM_DEBUG rounding check has to be adapted to only trigger if no
uprounding happend.

Signed-off-by: Uwe Kleine-König <[email protected]>
Tested-by: Trevor Gamblin <[email protected]>
Link: https://lore.kernel.org/r/353dc6ae31be815e41fd3df89c257127ca0d1a09.1743844730.git.u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König <[email protected]>

Author: ukleinek

drivers/pwm/core.c

@@ -322,7 +322,7 @@ static int __pwm_set_waveform(struct pwm_device *pwm,
 	const struct pwm_ops *ops = chip->ops;
 	char wfhw[WFHWSIZE];
 	struct pwm_waveform wf_rounded;
-	int err;
+	int err, ret_tohw;
 
 	BUG_ON(WFHWSIZE < ops->sizeof_wfhw);
 
@@ -332,16 +332,16 @@ static int __pwm_set_waveform(struct pwm_device *pwm,
 	if (!pwm_wf_valid(wf))
 		return -EINVAL;
 
-	err = __pwm_round_waveform_tohw(chip, pwm, wf, &wfhw);
-	if (err)
-		return err;
+	ret_tohw = __pwm_round_waveform_tohw(chip, pwm, wf, &wfhw);
+	if (ret_tohw < 0)
+		return ret_tohw;
 
 	if ((IS_ENABLED(CONFIG_PWM_DEBUG) || exact) && wf->period_length_ns) {
 		err = __pwm_round_waveform_fromhw(chip, pwm, &wfhw, &wf_rounded);
 		if (err)
 			return err;
 
-		if (IS_ENABLED(CONFIG_PWM_DEBUG) && !pwm_check_rounding(wf, &wf_rounded))
+		if (IS_ENABLED(CONFIG_PWM_DEBUG) && ret_tohw == 0 && !pwm_check_rounding(wf, &wf_rounded))
 			dev_err(&chip->dev, "Wrong rounding: requested %llu/%llu [+%llu], result %llu/%llu [+%llu]\n",
 				wf->duty_length_ns, wf->period_length_ns, wf->duty_offset_ns,
 				wf_rounded.duty_length_ns, wf_rounded.period_length_ns, wf_rounded.duty_offset_ns);
@@ -382,7 +382,8 @@ static int __pwm_set_waveform(struct pwm_device *pwm,
 				wf_rounded.duty_length_ns, wf_rounded.period_length_ns, wf_rounded.duty_offset_ns,
 				wf_set.duty_length_ns, wf_set.period_length_ns, wf_set.duty_offset_ns);
 	}
-	return 0;
+
+	return ret_tohw;
 }
 
 /**