linux-kernel - Re: [PATCH 1/4] dt-bindings: hwmon: Add Aspeed AST2600 PWM/Fan

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Message-ID: <20201215092545.GA24903@aspeedtech.com>
Date:   Tue, 15 Dec 2020 17:25:46 +0800
From:   Troy Lee <troy_lee@...eedtech.com>
To:     Rob Herring <robh@...nel.org>
CC:     "openbmc@...ts.ozlabs.org" <openbmc@...ts.ozlabs.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>,
        Jonathan Corbet <corbet@....net>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "open list:HARDWARE MONITORING" <linux-hwmon@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "moderated list:ARM/ASPEED MACHINE SUPPORT" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/ASPEED MACHINE SUPPORT" 
        <linux-aspeed@...ts.ozlabs.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        "leetroy@...il.com" <leetroy@...il.com>,
        "Ryan Chen" <ryan_chen@...eedtech.com>,
        ChiaWei Wang <chiawei_wang@...eedtech.com>,
        Billy Tsai <billy_tsai@...eedtech.com>
Subject: Re: [PATCH 1/4] dt-bindings: hwmon: Add Aspeed AST2600 PWM/Fan

The 12/11/2020 11:26, Rob Herring wrote:
> On Wed, Dec 09, 2020 at 03:59:17PM +0800, Troy Lee wrote:
> > For supporting a new AST2600 PWM/Fan hwmon driver, we add a new binding.
> > 
> > Signed-off-by: Troy Lee <troy_lee@...eedtech.com>
> > ---
> >  .../bindings/hwmon/aspeed2600-pwm-tacho.txt   | 69 +++++++++++++++++++
> 
> Bindings are in DT schema format now.
> 
I'll submit a new binding with DT schema.

> >  1 file changed, 69 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/hwmon/aspeed2600-pwm-tacho.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/hwmon/aspeed2600-pwm-tacho.txt b/Documentation/devicetree/bindings/hwmon/aspeed2600-pwm-tacho.txt
> > new file mode 100644
> > index 000000000000..61b11914352f
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/hwmon/aspeed2600-pwm-tacho.txt
> > @@ -0,0 +1,69 @@
> > +ASPEED AST2600 PWM and Fan Tacho controller device driver
> > +
> > +The ASPEED PWM controller can support upto 16 PWM outputs. The ASPEED Fan Tacho
> > +controller can support upto 16 Fan tachometer inputs.
> > +
> > +There can be upto 16 fans supported. Each fan can have one PWM output and
> > +one Fan tach inputs.
> > +
> > +Required properties for pwm-tacho node:
> > +- #address-cells : should be 1.
> > +
> > +- #size-cells : should be 0.
> > +
> > +- #cooling-cells: should be 2.
> > +
> > +- reg : address and length of the register set for the device.
> > +
> > +- pinctrl-names : a pinctrl state named "default" must be defined.
> > +
> > +- pinctrl-0 : phandle referencing pin configuration of the PWM ports.
> > +
> > +- compatible : should be "aspeed,ast2600-pwm-tachometer".
> > +
> > +- clocks : phandle to clock provider with the clock number in the second cell
> > +
> > +- resets : phandle to reset controller with the reset number in the second cell
> > +
> > +fan subnode format:
> > +===================
> > +Under fan subnode there can upto 16 child nodes, with each child node
> > +representing a fan. There are 16 fans each fan can have one PWM port and one
> > +Fan tach inputs.
> > +For PWM port can be configured cooling-levels to create cooling device.
> > +Cooling device could be bound to a thermal zone for the thermal control.
> > +
> > +Required properties for each child node:
> > +- reg : should specify PWM source port.
> > +	integer value in the range 0x00 to 0x0f with 0x00 indicating PWM port 0
> > +	and 0x0f indicating PWM port F.
> > +
> > +- cooling-levels: PWM duty cycle values in a range from 0 to 255
> > +                  which correspond to thermal cooling states.
> > +
> > +- aspeed,fan-tach-ch : should specify the Fan tach input channel.
> > +                integer value in the range 0 through 15, with 0 indicating
> > +		Fan tach channel 0 and 15 indicating Fan tach channel 15.
> > +		Atleast one Fan tach input channel is required.
> 
> Already has 'fan-tach-ch' in npcm750-pwm-fan.txt.
> 
OK.

> > +
> > +- aspeed,target-pwm : Specify the frequency of PWM. The value range from 24 to
> > +		      780000. Default value will be set to 25000.
> > +
> > +- aspeed,pulse-pr : Specify tacho pulse per revolution of the fan. A general
> > +		    parameter of pulse-pr is 2.
> 
> Already have 'pulses-per-revolution' property in pwm-fan.txt. Use that.
> 
OK.

> Really, all these should be in a common fan schema that you reference.
> 
Are you suggesting that I should also update these properties into
pwm-fan.txt with a separeated patch, perhaps?

> > +
> > +Examples:
> > +
> > +&pwm_tacho {
> > +	status = "okay";
> 
> Don't show status in examples.
> 
Understood, it will be removed in v2.

> > +	pinctrl-names = "default";
> > +	pinctrl-0 = <&pinctrl_pwm0_default &pinctrl_tach0_default>;
> > +
> > +	fan@0 {
> > +		reg = <0x00>;
> > +		aspeed,target-pwm = <25000>;
> > +		cooling-levels = /bits/ 8 <125 151 177 203 229 255>;
> > +		aspeed,fan-tach-ch = /bits/ 8 <0x00>;
> > +		aspeed,pulse-pr = <2>;
> > +	};
> > +};
> > -- 
> > 2.17.1
> >