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

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Message-ID: <8871faad-5785-62c3-5afa-8c248ac79e9a@ti.com>
Date:   Wed, 24 Aug 2022 14:45:08 +0530
From:   Vignesh Raghavendra <vigneshr@...com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        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 24/08/22 12:42, Krzysztof Kozlowski wrote:
> 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...

Understood, just wanted to make sure what the latest stance is, as I see
lot of files in arm64 dts folder still use bootargs and earlycon. Thanks
for the clarification!

-- 
Regards
Vignesh