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From:   Douglas Anderson <dianders@chromium.org>
To:     gregkh@linuxfoundation.org
Cc:     mka@chromium.org, swboyd@chromium.org, ryandcase@chromium.org,
        bjorn.andersson@linaro.org, akashast@codeaurora.org,
        skakit@codeaurora.org, rojay@codeaurora.org,
        mgautam@codeaurora.org, Douglas Anderson <dianders@chromium.org>,
        Andy Gross <agross@kernel.org>,
        Doug Anderson <dianders@google.com>,
        Girish Mahadevan <girishm@codeaurora.org>,
        Jiri Slaby <jslaby@suse.com>,
        Karthikeyan Ramasubramanian <kramasub@codeaurora.org>,
        Sagar Dharia <sdharia@codeaurora.org>,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-serial@vger.kernel.org
Subject: [PATCH 1/2] tty: serial: qcom_geni_serial: No need to stop tx/rx on UART shutdown
Date:   Fri, 13 Mar 2020 13:46:51 -0700
Message-Id: <20200313134635.1.Icf54c533065306b02b880c46dfd401d8db34e213@changeid>
MIME-Version: 1.0
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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@chromium.org>
---

 drivers/tty/serial/qcom_geni_serial.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index 272bae0eebc7..09d8612517aa 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -827,17 +827,11 @@ static void get_tx_fifo_size(struct qcom_geni_serial_port *port)
 
 static void qcom_geni_serial_shutdown(struct uart_port *uport)
 {
-	unsigned long flags;
-
 	/* Stop the console before stopping the current tx */
 	if (uart_console(uport))
 		console_stop(uport->cons);
 
 	disable_irq(uport->irq);
-	spin_lock_irqsave(&uport->lock, flags);
-	qcom_geni_serial_stop_tx(uport);
-	qcom_geni_serial_stop_rx(uport);
-	spin_unlock_irqrestore(&uport->lock, flags);
 }
 
 static int qcom_geni_serial_port_setup(struct uart_port *uport)
-- 
2.25.1.481.gfbce0eb801-goog