linux-kernel - Re: [PATCH v12 04/10] pwm: max7360: Add MAX7360 PWM support

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Message-ID: <2msg7e7q42ocjewv35rytdtxwrfqrndpm2y5ustqeaeodencsd@nfdufgtevxte>
Date: Fri, 1 Aug 2025 12:11:48 +0200
From: Uwe Kleine-König <ukleinek@...nel.org>
To: Mathieu Dubois-Briand <mathieu.dubois-briand@...tlin.com>
Cc: Lee Jones <lee@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Kamel Bouhara <kamel.bouhara@...tlin.com>, Linus Walleij <linus.walleij@...aro.org>, 
	Bartosz Golaszewski <brgl@...ev.pl>, Dmitry Torokhov <dmitry.torokhov@...il.com>, 
	Michael Walle <mwalle@...nel.org>, Mark Brown <broonie@...nel.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Danilo Krummrich <dakr@...nel.org>, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-gpio@...r.kernel.org, linux-input@...r.kernel.org, linux-pwm@...r.kernel.org, 
	andriy.shevchenko@...el.com, Grégory Clement <gregory.clement@...tlin.com>, 
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v12 04/10] pwm: max7360: Add MAX7360 PWM support

On Tue, Jul 22, 2025 at 06:23:48PM +0200, Mathieu Dubois-Briand wrote:
> +static int max7360_pwm_round_waveform_tohw(struct pwm_chip *chip,
> +					   struct pwm_device *pwm,
> +					   const struct pwm_waveform *wf,
> +					   void *_wfhw)
> +{
> +	struct max7360_pwm_waveform *wfhw = _wfhw;
> +	u64 duty_steps;
> +
> +	/*
> +	 * Ignore user provided values for period_length_ns and duty_offset_ns:
> +	 * we only support fixed period of MAX7360_PWM_PERIOD_NS and offset of 0.
> +	 * Values from 0 to 254 as duty_steps will provide duty cycles of 0/256
> +	 * to 254/256, while value 255 will provide a duty cycle of 100%.
> +	 */
> +	if (wf->duty_length_ns >= MAX7360_PWM_PERIOD_NS) {
> +		duty_steps = MAX7360_PWM_MAX;
> +	} else {
> +		duty_steps = (u32)wf->duty_length_ns * MAX7360_PWM_STEPS / MAX7360_PWM_PERIOD_NS;
> +		if (duty_steps == MAX7360_PWM_MAX)
> +			duty_steps = MAX7360_PWM_MAX - 1;
> +	}
> +
> +	wfhw->duty_steps = min(MAX7360_PWM_MAX, duty_steps);
> +	wfhw->enabled = !!wf->period_length_ns;
> +
> +	return 0;

The unconditional return 0 is wrong and testing with PWM_DEBUG enabled
should tell you that.

I think the right thing to do here is:

	if (wf->period_length_ns > MAX7360_PWM_PERIOD_NS)
		return 1;
	else
		return 0;

Otherwise looks fine.

Best regards
Uwe

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