Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Sender: Guenter Roeck <groeck7@gmail.com>
Message-ID: <f76f89a0-7773-6f64-c890-293093d4aba3@roeck-us.net>
Date:   Thu, 8 Jun 2023 06:18:10 -0700
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.10.0
Subject: Re: [v6 2/4] dt-bindings: hwmon: Add ASPEED TACH Control
 documentation
Content-Language: en-US
To:     Billy Tsai <billy_tsai@aspeedtech.com>,
        "jdelvare@suse.com" <jdelvare@suse.com>,
        "robh+dt@kernel.org" <robh+dt@kernel.org>,
        "krzysztof.kozlowski+dt@linaro.org" 
        <krzysztof.kozlowski+dt@linaro.org>,
        "joel@jms.id.au" <joel@jms.id.au>,
        "andrew@aj.id.au" <andrew@aj.id.au>,
        "thierry.reding@gmail.com" <thierry.reding@gmail.com>,
        "u.kleine-koenig@pengutronix.de" <u.kleine-koenig@pengutronix.de>,
        "corbet@lwn.net" <corbet@lwn.net>,
        "p.zabel@pengutronix.de" <p.zabel@pengutronix.de>,
        "linux-hwmon@vger.kernel.org" <linux-hwmon@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-aspeed@lists.ozlabs.org" <linux-aspeed@lists.ozlabs.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-pwm@vger.kernel.org" <linux-pwm@vger.kernel.org>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        "patrick@stwcx.xyz" <patrick@stwcx.xyz>
References: <20230608021839.12769-1-billy_tsai@aspeedtech.com>
 <20230608021839.12769-3-billy_tsai@aspeedtech.com>
 <c1c485b0-b68b-4db7-4b67-5d59f1ecb84e@roeck-us.net>
 <SG2PR06MB3365E360F3FCDE639F3D2D1E8B50A@SG2PR06MB3365.apcprd06.prod.outlook.com>
From:   Guenter Roeck <linux@roeck-us.net>
In-Reply-To: <SG2PR06MB3365E360F3FCDE639F3D2D1E8B50A@SG2PR06MB3365.apcprd06.prod.outlook.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 6/7/23 23:21, Billy Tsai wrote:
>          > The code says:
> 
>          > In Aspeed AST2600 SoC features 16 TACH controllers, with each
> 
>          > controller capable of supporting up to 1 input.
> 
>          > which is a bit different. I guess there are no examples anymore,
> 
>          > but I'd really like to see how this looks like in the devicetree file,
> 
>          > and how the driver is supposed to distinguish/select the 16 inputs.
> 
> Hi Roeck,
> 
> The node in the devicetree file will looks like following:
> 
> tach0: tach0@1e610008 {
> 
>          compatible = "aspeed,ast2600-tach";
> 
>          reg = <0x1e610008 0x8>;
> 
>          #address-cells = <1>;
> 
>          #size-cells = <0>;
> 
>          pinctrl-names = "default";
> 
>          pinctrl-0 = <&pinctrl_tach0_default>;
> 
>          clocks = <&syscon ASPEED_CLK_AHB>;
> 
>          resets = <&syscon ASPEED_RESET_PWM>;
> 
>          status = "disabled";
> 
> };
> 

Neither reg nor pinctrl is mentioned in the bindings. Maybe that is not needed nowadays,
but I find it confusing.

Either case, it is highly unusual that there would be 16 instances of this device
instead of one. Why is this done ? It doesn't really make sense to me.

Guenter