linux-kernel - Re: [PATCH] tty: serial: qcom_geni_serial: 115.2 is a better console default than 9600

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Message-ID: <981cfc91-035e-57cb-5972-e2a749adae98@codeaurora.org>
Date:   Mon, 14 Sep 2020 15:29:25 +0530
From:   Akash Asthana <akashast@...eaurora.org>
To:     Douglas Anderson <dianders@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>, robdclark@...omium.org,
        Nathan Chancellor <natechancellor@...il.com>,
        jwerner@...omium.org, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH] tty: serial: qcom_geni_serial: 115.2 is a better console
 default than 9600


On 9/11/2020 8:30 PM, Douglas Anderson wrote:
> Commit c5cbc78acf69 ("tty: serial: qcom_geni_serial: Initialize baud
> in qcom_geni_console_setup") fixed a bug by initting a variable that
> was used in some cases without initialization.  However, the "default"
> baud rate picked by that CL was probably not the best choice.  The
> chances that anyone out there is trying to run a system with kernel
> messages piped out over a 9600 baud serial port is just about nil.
> Console messages are printed in a blocking manner.  At 9600 baud we
> print about 1 character per millisecond which means that printing a
> 40-byte message to the console will take ~40 ms.  While it would
> probably work, it's going to make boot _very_ slow and probably cause
> the occasional timeout here and there in drivers (heck, even at 115200
> console delays can wreck havoc).
>
> This has already bit at least two people that I'm aware of that tried
> to enable serial console by just adding "console=ttyMSM0" (instead of
> "console=ttyMSM0,115200n8") to the command line, so it seems like it'd
> be nice to fix.
>
> Let's switch the default to 115200.
Reviewed-by: Akash Asthana <akashast@...eaurora.org>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
>
>
-- 
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