linux-kernel - Re: [PATCH] arm64: dts: imx8mm-evk: add pwm1/backlight support

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Date:   Wed, 13 Apr 2022 14:27:00 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Tommaso Merciai <tommaso.merciai@...rulasolutions.com>
Cc:     linux-amarula@...rulasolutions.com,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Joakim Zhang <qiangqing.zhang@....com>,
        Tim Harvey <tharvey@...eworks.com>,
        Richard Zhu <hongxing.zhu@....com>, Li Jun <jun.li@....com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: imx8mm-evk: add pwm1/backlight support

On 13/04/2022 13:58, Tommaso Merciai wrote:
>>> +	backlight: backlight {
>>> +		status = "disabled";
>>
>> Why disabled?
>>
>>> +		compatible = "pwm-backlight";
>>> +		pwms = <&pwm1 0 5000000>;
>>> +		brightness-levels = <0 255>;
>>> +		num-interpolated-steps = <255>;
>>> +		default-brightness-level = <250>;
>>> +	};
>>> +
>>>  	ir-receiver {
>>>  		compatible = "gpio-ir-receiver";
>>>  		gpios = <&gpio1 13 GPIO_ACTIVE_LOW>;
>>> @@ -395,6 +404,12 @@ &wdog1 {
>>>  	status = "okay";
>>>  };
>>>  
>>> +&pwm1 {
>>> +	pinctrl-names = "default";
>>> +	pinctrl-0 = <&pinctrl_backlight>;
>>> +	status = "disabled";
>>
>> Same here.
>>
>>
>> Best regards,
>> Krzysztof
> 
> Hi Krzysztof,
> I think is better to keep disable into .dtsi and enable it at .dts
> level.
> What do you think about?

Why better? This is already board DTSI, not a SoC DTSI. All boards using
it are supposed to have it available, aren't they?

Usually nodes should be disabled in a DTSI if they need some resources
not available in that DTSI. For example if they need some supply. It's
not the case here, right?


Best regards,
Krzysztof