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Message-ID: <52d83a29-0f16-cd4c-9810-7c6bd497fe85@brixit.nl>
Date:   Tue, 4 Apr 2023 13:31:05 +0200
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Subject: Re: [PATCH] arm64: dts: rockchip: Change serial baud rate for
 Pinephone Pro to 1.5 MB
To:     =?UTF-8?Q?Heiko_St=c3=bcbner?= <heiko@sntech.de>,
        linux-kernel@vger.kernel.org,
        Javier Martinez Canillas <javierm@redhat.com>
Cc:     Peter Robinson <pbrobinson@gmail.com>,
        Caleb Connolly <kc@postmarketos.org>,
        Jarrah Gosbell <kernel@undef.tools>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        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
References: <20230403175937.2842085-1-javierm@redhat.com>
 <3738011.44csPzL39Z@diego>
Content-Language: en-US
From:   Martijn Braam <martijn@brixit.nl>
In-Reply-To: <3738011.44csPzL39Z@diego>
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On 4/4/23 09:51, Heiko Stübner 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
of having a few devices at weird baudrates and the bootloader already
starts outputting debug logs at 115200 baud.

>
> Personally I don't care that much either way, but would like a comment
> from the other people working on that device - if possible.
>
> I guess if we don't hear anything, I'll apply it nevertheless at some point
>
>
> Heiko
>
>
>> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
>> ---
>>
>> I tried to instead get rid of the baud rate altogether, as suggested by
>> Peter Robinson. AFAIU that should just pick whatever bad rate has been
>> using by the early console.
>>
>> But neither using 'stdout-path = "serial2" nor 'stdout-path = &uart2'
>> worked for me.
>>
>> In both cases I didn't have any output unless setting a baud rate using
>> the 'console='param.
>>
>>   arch/arm64/boot/dts/rockchip/rk3399-pinephone-pro.dts | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/boot/dts/rockchip/rk3399-pinephone-pro.dts b/arch/arm64/boot/dts/rockchip/rk3399-pinephone-pro.dts
>> index a0795a2b1cb1..6bbe65bd5bd4 100644
>> --- a/arch/arm64/boot/dts/rockchip/rk3399-pinephone-pro.dts
>> +++ b/arch/arm64/boot/dts/rockchip/rk3399-pinephone-pro.dts
>> @@ -26,7 +26,7 @@ aliases {
>>   	};
>>   
>>   	chosen {
>> -		stdout-path = "serial2:115200n8";
>> +		stdout-path = "serial2:1500000n8";
>>   	};
>>   
>>   	gpio-keys {
>>
>> base-commit: 3adf89324a2b2a9dbc2c12d8895021e7e34e3346
>>
>
>
>