linux-kernel - Re: [PATCH v2 1/2] dt-bindings: hwmon: amc6821: add PWM polarity

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Message-ID: <20250226135806.GA47264@francesco-nb>
Date: Wed, 26 Feb 2025 14:58:06 +0100
From: Francesco Dolcini <francesco@...cini.it>
To: Rob Herring <robh@...nel.org>
Cc: Francesco Dolcini <francesco@...cini.it>,
	Jean Delvare <jdelvare@...e.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Farouk Bouabid <farouk.bouabid@...rry.de>,
	Quentin Schulz <quentin.schulz@...rry.de>,
	Francesco Dolcini <francesco.dolcini@...adex.com>,
	linux-hwmon@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] dt-bindings: hwmon: amc6821: add PWM polarity

On Wed, Feb 26, 2025 at 07:49:22AM -0600, Rob Herring wrote:
> On Mon, Feb 24, 2025 at 07:08:00PM +0100, Francesco Dolcini wrote:
> > From: Francesco Dolcini <francesco.dolcini@...adex.com>
> > 
> > Add property to describe the PWM-Out pin polarity.
> 
> Why doesn't the invert support in the pwm binding work for you? Yes, I 
> read the discussion, but don't remember the conclusion and you need to 
> justify it here.

This chip is not a PWM controller, it is a FAN controller.

The HW has a PWM pin output that is used to control the fan, but the
device is not modelled as a PWM controller (correctly, given that is not
such a device) and the OS does not control the PWM, the chip reads the
temperature and decide the PWM duty cycle accordingly in an autonomous
way.

It's just the same that was done in commit ed39ff506adb ("dt-bindings:
hwmon: Document adt7475 pwm-active-state property").

Francesco