linux-kernel - Re: [PATCH 2/2] arm64: dts: mediatek: mt7988: add PWM controller

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Date: Wed, 14 Feb 2024 10:24:32 +0100
From: Rafał Miłecki <zajec5@...il.com>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Matthias Brugger <matthias.bgg@...il.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc: John Crispin <john@...ozen.org>, linux-pwm@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org,
 Rafał Miłecki <rafal@...ecki.pl>
Subject: Re: [PATCH 2/2] arm64: dts: mediatek: mt7988: add PWM controller

On 14.02.2024 10:09, AngeloGioacchino Del Regno wrote:
> Il 13/02/24 17:46, Rafał Miłecki ha scritto:
>> From: Rafał Miłecki <rafal@...ecki.pl>
>>
>> Add binding for on-SoC controller that can control up to 8 PWMs.
>>
>> Signed-off-by: Rafał Miłecki <rafal@...ecki.pl>
>> ---
>>   arch/arm64/boot/dts/mediatek/mt7988a.dtsi | 21 ++++++++++++++++++++-
>>   1 file changed, 20 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/boot/dts/mediatek/mt7988a.dtsi b/arch/arm64/boot/dts/mediatek/mt7988a.dtsi
>> index bba97de4fb44..67007626b5cd 100644
>> --- a/arch/arm64/boot/dts/mediatek/mt7988a.dtsi
>> +++ b/arch/arm64/boot/dts/mediatek/mt7988a.dtsi
>> @@ -1,5 +1,6 @@
>>   // SPDX-License-Identifier: GPL-2.0-only OR MIT
>> +#include <dt-bindings/clock/mediatek,mt7988-clk.h>
>>   #include <dt-bindings/interrupt-controller/arm-gic.h>
>>   / {
>> @@ -78,7 +79,7 @@ gic: interrupt-controller@...0000 {
>>               #interrupt-cells = <3>;
>>           };
>> -        clock-controller@...01000 {
>> +        infracfg: clock-controller@...01000 {
>>               compatible = "mediatek,mt7988-infracfg", "syscon";
>>               reg = <0 0x10001000 0 0x1000>;
>>               #clock-cells = <1>;
>> @@ -103,6 +104,24 @@ clock-controller@...1e000 {
>>               #clock-cells = <1>;
>>           };
>> +        pwm@...48000 {
>> +            compatible = "mediatek,mt7988-pwm";
> 
> I can't take this unless there's a driver that supports your device.

I'd argue you should rather look for a documented binding rather than a
(Linux?) driver. Otherwise you would refuse changes that are not
strictly Linux related. DTS files are meant to describe hardware in a
generic way and not be driven by Linux drivers / design.

Example:
We have bindings for "brcm,bcm6345-timer" and "bcm63138-timer" (see
commit e112f2de151b) and DTS files with those bindings.
There is no Linux driver for that hardware block as there is no need
for it.


In this context I'm explaining binding thing with Conor in discussion
on PATCH 1/1. So stay tuned :)