linux-kernel - Re: [PATCH v3 2/2] ARM: dts: aspeed: Add device tree for Ampere's Mt. Mitchell BMC

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Message-ID: <673e200f-f458-7866-f956-3d5bd7160a49@os.amperecomputing.com>
Date:   Tue, 23 Aug 2022 15:27:32 +0700
From:   Quan Nguyen <quan@...amperecomputing.com>
To:     Arnd Bergmann <arnd@...db.de>, Joel Stanley <joel@....id.au>
Cc:     openbmc@...ts.ozlabs.org, Olof Johansson <olof@...om.net>,
        soc@...nel.org, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Andrew Jeffery <andrew@...id.au>,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-aspeed@...ts.ozlabs.org,
        Open Source Submission <patches@...erecomputing.com>,
        Phong Vo <phong@...amperecomputing.com>,
        thang@...amperecomputing.com
Subject: Re: [PATCH v3 2/2] ARM: dts: aspeed: Add device tree for Ampere's Mt.
 Mitchell BMC



On 18/08/2022 19:06, Arnd Bergmann wrote:
> On Thu, Aug 18, 2022 at 9:33 AM Joel Stanley <joel@....id.au> wrote:
>>> +
>>> +/ {
>>> +       model = "Ampere Mt.Mitchell BMC";
>>> +       compatible = "ampere,mtmitchell-bmc", "aspeed,ast2600";
>>> +
>>> +       chosen {
>>> +               stdout-path = &uart5;
>>
>> I know you've been told by Arnd and others to remove the default
>> command line here, but without it your device tree fails to produce
>> any output in my tests:
>>
>> qemu-system-arm -M ast2600-evb -nographic -dtb
>> arch/arm/boot/dts/aspeed-bmc-ampere-mtmitchell.dtb -kernel
>> arch/arm/boot/zImage
>>
>> Without a working test, I can't tell the difference between a broken
>> device tree and one that omits the serial device on the command line.
>> Can you work with Arnd to come to a solution here?
> 
> If you use qemu as the boot loader, I think the expected way to do
> this is to use the "-append" command line argument along with "-kernel".
> 
> Is there any reason for this machine to be special here?
> 

Thanks Arnd for the comment.

I think adding -append could solve the issue.

But as the bootargs still exist in all other 
arch/arm/boot/dts/aspeed-bmc-*.dts should we still keep bootargs for 
this dts?

Thanks,
- Quan