linux-kernel - Re: [PATCH 4/4] arch: arm64: ti: Add support for J784s4 EVM board

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Message-ID: <81134eb9-2b7d-05bc-3035-a47f020861a8@linaro.org>
Date:   Wed, 24 Aug 2022 10:12:41 +0300
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Vignesh Raghavendra <vigneshr@...com>, Nishanth Menon <nm@...com>
Cc:     Apurva Nandan <a-nandan@...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 4/4] arch: arm64: ti: Add support for J784s4 EVM board

On 24/08/2022 08:33, Vignesh Raghavendra wrote:
> Hi Krzysztof,
> 
> On 24/08/22 10:36, Nishanth Menon wrote:
>> On 13:21-20220823, Krzysztof Kozlowski wrote:
>>>> +
>>>> +/ {
>>>> +	compatible = "ti,j784s4-evm", "ti,j784s4";
>>>> +	model = "Texas Instruments J784S4 EVM";
>>>> +
>>>> +	chosen {
>>>> +		stdout-path = "serial2:115200n8";
>>>> +		bootargs = "console=ttyS2,115200n8 earlycon=ns16550a,mmio32,0x2880000";
>>>
>>> earlycon is not a property of hardware. Console is defined in
> 
> earlycon is helpful for debugging early crashes. How is it any different
> from "console =" property as described in
> Documentation/devicetree/usage-model.rst?

choice of console is needed for basic operation and is chosen based on
current hardware setup. earlycon is purely for debugging and should be
enabled only when debugging is intended, not on mainline wide-available
sources.

> 
>>> stdout-path, so please drop entire bootargs.
>>
>> We will probably have to cleanup elsewhere as well - point noted.
>>
> 
> Whats the alternative to pass default bootargs to kernel if bootloader
> does not pass bootargs via cmdline? I see quite a few dts file use
> bootargs = "earlycon" at least

Uboot, your own out-of-tree testing patches? What's the point to have
earlycon available for every user which does not want to debug?

Sorry, but bootargs are not accepted in DTS. We have several discussions
around it over time...


Best regards,
Krzysztof