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From:   Javier Martinez Canillas <javierm@redhat.com>
To:     Heiko =?utf-8?Q?St=C3=BCbner?= <heiko@sntech.de>,
        linux-kernel@vger.kernel.org
Cc:     Peter Robinson <pbrobinson@gmail.com>,
        Caleb Connolly <kc@postmarketos.org>,
        Jarrah Gosbell <kernel@undef.tools>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Martijn Braam <martijn@brixit.nl>, Ondrej Jirman <megi@xff.cz>,
        Rob Herring <robh+dt@kernel.org>,
        Tom Fitzhenry <tom@tom-fitzhenry.me.uk>,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-rockchip@lists.infradead.org
Subject: Re: [PATCH] arm64: dts: rockchip: Change serial baud rate for
 Pinephone Pro to 1.5 MB
In-Reply-To: <3738011.44csPzL39Z@diego>
References: <20230403175937.2842085-1-javierm@redhat.com>
 <3738011.44csPzL39Z@diego>
Date:   Tue, 04 Apr 2023 10:08:25 +0200
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Heiko St=C3=BCbner <heiko@sntech.de> writes:

Hello Heiko,

Thanks for your feedback.

> Hi,
>
> Am Montag, 3. April 2023, 19:59:37 CEST schrieb Javier Martinez Canillas:
>> This baud rate is set for the device by mainline u-boot and is also what
>> is set in the Pinebook Pro Device Tree, which is a device similar to the
>> PinePhone Pro but with a different form factor.
>>=20
>> Otherwise, the baud rate of the firmware and Linux don't match by default
>> and a 'console=3DttyS2,1500000n8' kernel command line parameter is requi=
red
>> to have proper output for both.
>
> The interesting question is always if this will break someone else's setu=
p.

Indeed.

> I've never really understood the strange setting of 1.5MBps, but on the
> other hand it _is_ a reality on most boards.
>

As far as I understand, it is just to get a faster data transmission but I
have my doubts that it is worth to divert from the more common 115200 rate
just for this.

As you said though, it is a reality and also what mainline u-boot uses for
this device.

> Personally I don't care that much either way, but would like a comment
> from the other people working on that device - if possible.
>

Same, I don't care either but just that would be good to make Linux and
u-boot to match. If this change will break other people setups, maybe I
can convince u-boot to sync with Linux and also use 115200 for the phone.

> I guess if we don't hear anything, I'll apply it nevertheless at some poi=
nt
>
>
> Heiko
>

--=20
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat