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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Thu, 18 Aug 2022 14:06:40 +0200
Message-ID: <CAK8P3a2LZKfZpdTQ-R4o9mJ6dk52VRF+Bxj=PJEx-1MA4yH8+w@mail.gmail.com>
Subject: Re: [PATCH v3 2/2] ARM: dts: aspeed: Add device tree for Ampere's Mt.
 Mitchell BMC
To:     Joel Stanley <joel@jms.id.au>
Cc:     Quan Nguyen <quan@os.amperecomputing.com>,
        Arnd Bergmann <arnd@arndb.de>, openbmc@lists.ozlabs.org,
        Olof Johansson <olof@lixom.net>, soc@kernel.org,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Andrew Jeffery <andrew@aj.id.au>,
        linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-aspeed@lists.ozlabs.org,
        Open Source Submission <patches@amperecomputing.com>,
        Phong Vo <phong@os.amperecomputing.com>,
        thang@os.amperecomputing.com
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On Thu, Aug 18, 2022 at 9:33 AM Joel Stanley <joel@jms.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?

       Arnd