linux-kernel - Re: [PATCH v2 1/3] mips: dts: ralink: mt7621: associate uart1

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Message-ID: <9634b4fe726e711bd6bec7e487caab76@risingedge.co.za>
Date: Fri, 08 Mar 2024 14:40:29 +0200
From: Justin Swartz <justin.swartz@...ingedge.co.za>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: Arınç ÜNAL <arinc.unal@...nc9.com>, Sergio
 Paracuellos <sergio.paracuellos@...il.com>, Rob Herring
 <robh+dt@...nel.org>, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>,
 Thomas Bogendoerfer <tsbogend@...ha.franken.de>, Matthias Brugger
 <matthias.bgg@...il.com>, linux-mips@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v2 1/3] mips: dts: ralink: mt7621: associate uart1_pins
 with serial0

Hi Angelo

On 2024-03-08 10:41, AngeloGioacchino Del Regno wrote:
> Il 07/03/24 20:04, Justin Swartz ha scritto:
>> Add missing pinctrl-name and pinctrl-0 properties to declare
>> that the uart1_pins group is associated with serial0.
>> 
>> Signed-off-by: Justin Swartz <justin.swartz@...ingedge.co.za>
>> ---
>>   arch/mips/boot/dts/ralink/mt7621.dtsi | 3 +++
>>   1 file changed, 3 insertions(+)
>> 
>> diff --git a/arch/mips/boot/dts/ralink/mt7621.dtsi 
>> b/arch/mips/boot/dts/ralink/mt7621.dtsi
>> index 35a10258f..dca415fdd 100644
>> --- a/arch/mips/boot/dts/ralink/mt7621.dtsi
>> +++ b/arch/mips/boot/dts/ralink/mt7621.dtsi
>> @@ -123,6 +123,9 @@ serial0: serial@c00 {
>>   			reg-shift = <2>;
>>   			reg-io-width = <4>;
>>   			no-loopback-test;
>> +
>> +			pinctrl-names = "default";
>> +			pinctrl-0 = <&uart1_pins>;
>>   		};
>>     		spi0: spi@b00 {
> 
> The pins are muxed and can be either UART, or some other function that
> is supported by the mux: this means that the pinctrl-xxx properties 
> shall
> *not* go into the SoC dtsi file, but in board dts files instead.
> 
> Said differently: the usage of the UART pins is board-specific, not 
> SoC-wide.

Thanks for the explanation. I agree that the pinctrl properties
would make more sense in a serial node extension in a board's dts,
but my reason for including them in the SoC's dtsi is due to the
precedent set with these existing nodes:

   i2c
   spi0
   mmc
   ethernet
   pcie

There is also a default function declared for each of the pin
groups defined under the pinctrl node. These functions co-incide
with what is intended for each of those device nodes to function
correctly, rather than in the alternative GPIO-mode.

So I thought that sticking with that existing pattern would get
the least resistance from the community.

I can imagine how moving the pinctrl node to the board dts, and
then moving all of the pinctrl properties associated with device
nodes to their board dts references could be a better separation
logically.

What do you recommend?

Regards
Justin