linux-kernel - Re: [v6 1/2] dt-bindings: Add bindings for aspeed pwm-tach.

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Date:   Thu, 20 May 2021 01:06:43 +0000
From:   Billy Tsai <billy_tsai@...eedtech.com>
To:     Rob Herring <robh@...nel.org>
CC:     "lee.jones@...aro.org" <lee.jones@...aro.org>,
        "joel@....id.au" <joel@....id.au>,
        "andrew@...id.au" <andrew@...id.au>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        "u.kleine-koenig@...gutronix.de" <u.kleine-koenig@...gutronix.de>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
        BMC-SW <BMC-SW@...eedtech.com>
Subject: Re: [v6 1/2] dt-bindings: Add bindings for aspeed pwm-tach.

Hi Rob,

On 2021/5/20, 4:20 AM,Rob Herringwrote:

    On Tue, May 18, 2021 at 08:55:16AM +0800, Billy Tsai wrote:
    >   > +        };
    >   > +      };
    >   > +
    >   > +      tach: tach {
    >   > +        compatible = "aspeed,ast2600-tach";

    > Are pwm and tach separate h/w blocks? 

Yes, they are the separate h/w blocks.

    >   > +        #address-cells = <1>;
    >   > +        #size-cells = <0>;
    >   > +        pinctrl-names = "default";
    >   > +        pinctrl-0 = <&pinctrl_tach0_default>;
    >   > +        fan@0 {
    >   > +          reg = <0>;

    > How does one configure which PWM is connected to each fan?
    > Existing bindings use 'reg' for PWM channel and another property for 
    > tach channel. Please don't do something different.

The fan node in this place specifically refers tach pin, maybe I need to change the naming to avoid confusion.
We just focus on the fan properties on this tach channel has nothing to do with pwm.

    > +          aspeed,min-rpm = <1000>;
    > +          aspeed,pulse-pr = <2>;
    > +          aspeed,tach-div = <5>;
    > +        };
    > +      };
    > +    };