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Date:   Tue, 4 Apr 2023 14:02:31 +0200
From:   =?utf-8?Q?Ond=C5=99ej?= Jirman <megi@xff.cz>
To:     Javier Martinez Canillas <javierm@redhat.com>
Cc:     Martijn Braam <martijn@brixit.nl>,
        Heiko =?utf-8?Q?St=C3=BCbner?= <heiko@sntech.de>,
        linux-kernel@vger.kernel.org,
        Peter Robinson <pbrobinson@gmail.com>,
        Caleb Connolly <kc@postmarketos.org>,
        Jarrah Gosbell <kernel@undef.tools>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        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
Message-ID: <20230404120231.2enpesad2lhde6sb@core>
Mail-Followup-To: =?utf-8?Q?Ond=C5=99ej?= Jirman <megi@xff.cz>,
        Javier Martinez Canillas <javierm@redhat.com>,
        Martijn Braam <martijn@brixit.nl>,
        Heiko =?utf-8?Q?St=C3=BCbner?= <heiko@sntech.de>,
        linux-kernel@vger.kernel.org, Peter Robinson <pbrobinson@gmail.com>,
        Caleb Connolly <kc@postmarketos.org>,
        Jarrah Gosbell <kernel@undef.tools>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        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
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Hello,

On Tue, Apr 04, 2023 at 01:42:36PM +0200, Javier Martinez Canillas wrote:
> Martijn Braam <martijn@brixit.nl> writes:
> 
> > On 4/4/23 09:51, Heiko St?bner wrote:
> >> 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.
> >>>
> >>> Otherwise, the baud rate of the firmware and Linux don't match by default
> >>> and a 'console=ttyS2,1500000n8' kernel command line parameter is required
> >>> to have proper output for both.
> >> The interesting question is always if this will break someone else's setup.
> >> I've never really understood the strange setting of 1.5MBps, but on the
> >> other hand it _is_ a reality on most boards.
> >
> > It breaks my device test setup at least. The extra speed isn't worth the 
> > hassle
> 
> More than the extra speed is to have consistency accross all the rockchip
> devices in upstream and also sync with mainline u-boot.
> 
> > of having a few devices at weird baudrates and the bootloader already
> > starts outputting debug logs at 115200 baud.
> >
> 
> And mine starts outputting at 1.5MBps :) I guess that there isn't a one
> size fits all, so the question is whether the bikeshed color is what was
> painted in all other rockchip boards or the one that Tow-Boot has chosen.

For what it's worth, levinboot also defaults to 1.5 Mbaud.

  https://gitlab.com/DeltaGem/levinboot/-/blob/release/rk3399/entry.S#L65
  https://gitlab.com/DeltaGem/levinboot/-/blob/release/configure.py#L67

And it's very nice anything above >115200 is not broken by bad HW design,
like on original Pinephone, so this higher speed actually works. ;)

kind regards,
	o.

> -- 
> Best regards,
> 
> Javier Martinez Canillas
> Core Platforms
> Red Hat
>