linux-kernel - Re: [PATCH 1/2] tty: serial: qcom_geni_serial: No need to stop tx/rx on UART shutdown

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Message-ID: <158438145518.88485.3909168358047756949@swboyd.mtv.corp.google.com>
Date:   Mon, 16 Mar 2020 10:57:35 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Douglas Anderson <dianders@...omium.org>,
        gregkh@...uxfoundation.org
Cc:     mka@...omium.org, ryandcase@...omium.org,
        bjorn.andersson@...aro.org, akashast@...eaurora.org,
        skakit@...eaurora.org, rojay@...eaurora.org,
        mgautam@...eaurora.org, Douglas Anderson <dianders@...omium.org>,
        Andy Gross <agross@...nel.org>,
        Doug Anderson <dianders@...gle.com>,
        Girish Mahadevan <girishm@...eaurora.org>,
        Jiri Slaby <jslaby@...e.com>,
        Karthikeyan Ramasubramanian <kramasub@...eaurora.org>,
        Sagar Dharia <sdharia@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH 1/2] tty: serial: qcom_geni_serial: No need to stop tx/rx on UART shutdown

Quoting Douglas Anderson (2020-03-13 13:46:51)
> On a board using qcom_geni_serial I found that I could no longer
> interact with kdb if I got a crash after the "agetty" running on the
> same serial port was killed.  This meant that various classes of
> crashes that happened at reboot time were undebuggable.
> 
> Reading through the code, I couldn't figure out why qcom_geni_serial
> felt the need to run so much code at port shutdown time.  All we need
> to do is disable the interrupt.
> 
> After I make this change then a hardcoded kgdb_breakpoint in some late
> shutdown code now allows me to interact with the debugger.  I also
> could freely close / re-open the port without problems.
> 
> Fixes: c4f528795d1a ("tty: serial: msm_geni_serial: Add serial driver support for GENI based QUP")
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---

Matches what is described in Documentation/driver-api/serial/driver.rst

Reviewed-by: Stephen Boyd <swboyd@...omium.org>