linux-kernel - Re: [PATCH v3 4/4] arm64: dts: ti: Add support for J784S4 EVM board

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Date:   Fri, 18 Nov 2022 12:15:09 -0600
From:   Andrew Davis <afd@...com>
To:     Nishanth Menon <nm@...com>
CC:     Apurva Nandan <a-nandan@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Tero Kristo <kristo@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-gpio@...r.kernel.org>, Hari Nagalla <hnagalla@...com>
Subject: Re: [PATCH v3 4/4] arm64: dts: ti: Add support for J784S4 EVM board

On 11/18/22 12:08 PM, Nishanth Menon wrote:
> On 11:56-20221118, Andrew Davis wrote:
>> On 11/18/22 11:47 AM, Nishanth Menon wrote:
>>> On 11:40-20221118, Andrew Davis wrote:
>>>> On 11/16/22 7:04 AM, Apurva Nandan wrote:
>>>
>>> [...]
>>>
>>>>> +#include <dt-bindings/net/ti-dp83867.h>
>>>>> +#include <dt-bindings/gpio/gpio.h>
>>>>> +#include "k3-j784s4.dtsi"
>>>>> +
>>>>> +/ {
>>>>> +	compatible = "ti,j784s4-evm", "ti,j784s4";
>>>>> +	model = "Texas Instruments J784S4 EVM";
>>>>> +
>>>>> +	chosen {
>>>>> +		stdout-path = "serial2:115200n8";
>>>>> +	};
>>>>> +
>>>>> +	aliases {
>>>>> +		serial2 = &main_uart8;
>>>>
>>>> This feels hacky. Your chosen node picks serial2 as that is usually
>>>> the one that is wired up on K3 boards. But on this board it is main_uart8.
>>>> So why not have this be serial10, then choose
>>>>
>>>> stdout-path = "serial10:115200n8";
>>>>
>>>> Also, I've made comments on previous version of this series, it is
>>>> nice to include folks who have commented before in the CC for future
>>>> versions, that way our filters don't hide these away and we can more
>>>> easily check that our comments have been addressed.
>>>
>>> Please stick with the standard of serial2 as the linux console standard.
>>> We ended up with that to ease up capabilities of various distros to
>>> uniformly work across SoC and board variants.
>>>
>>
>> The chosen "stdout-path" is for setting the kernel's default output terminal.
>> Distros and other userspaces need to use their own policy mechanisms for
>> picking what serial port to run getty on or whatever the issue may be.
>>
>> Some look at the kernel command line, and our bootloader provides
>> that too, so still no reason to fake alias names here.
> 
> 
> We have had this conversation earlier as well.
> 
> https://lore.kernel.org/linux-arm-kernel/CAK8P3a2VSBvOn1o+q1PYZaQ6LS9U4cz+DZGuDbisHkwNs2dAAw@mail.gmail.com/T/#m4ecb0dc6a78c84631f072faa1b0df0df46333d09
> 
> This is also the reason why we picked serial2 as linux console as a
> standard across the boards based on the ecosystem.
> 

I don't see either of those addressed in that thread, only that
the aliases should go in the .dts files and be trimmed, nothing
stops us from:

chosen {
	stdout-path = "serial10:115200n8";
};

aliases {
	serial10 = &main_uart8;
};

Andrew