linux-kernel - [PATCH 23/24] tty: serial: fsl_lpuart: Don't enable TIE in .startup() or .resume()

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Date:   Mon, 29 Jul 2019 12:52:25 -0700
From:   Andrey Smirnov <andrew.smirnov@...il.com>
To:     linux-serial@...r.kernel.org
Cc:     Andrey Smirnov <andrew.smirnov@...il.com>,
        Stefan Agner <stefan@...er.ch>,
        Bhuvanchandra DV <bhuvanchandra.dv@...adex.com>,
        Chris Healy <cphealy@...il.com>,
        Cory Tusar <cory.tusar@....aero>,
        Lucas Stach <l.stach@...gutronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, linux-imx@....com,
        linux-kernel@...r.kernel.org
Subject: [PATCH 23/24] tty: serial: fsl_lpuart: Don't enable TIE in .startup() or .resume()

Enabling TIE in .startup() callback causes the driver to start (or at
least try) to transmit data before .start_tx() is called. Which, while
harmless (since TIE handler will immediately disable it), is a no-op
and shouldn't really happen. Drop UARTCR2_TIE from list of bits set in
lpuart_startup().

This change will also not enable TIE in .resume(), but it seems that,
similart to .startup(), transmit interrupt shouldn't be enabled there
either.

Signed-off-by: Andrey Smirnov <andrew.smirnov@...il.com>
Cc: Stefan Agner <stefan@...er.ch>
Cc: Bhuvanchandra DV <bhuvanchandra.dv@...adex.com>
Cc: Chris Healy <cphealy@...il.com>
Cc: Cory Tusar <cory.tusar@....aero>
Cc: Lucas Stach <l.stach@...gutronix.de>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Jiri Slaby <jslaby@...e.com>
Cc: linux-imx@....com
Cc: linux-serial@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
---
 drivers/tty/serial/fsl_lpuart.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 9643d4524e59..53b98065f9c5 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1409,7 +1409,7 @@ static void lpuart_setup_watermark_enable(struct lpuart_port *sport)
 	lpuart_setup_watermark(sport);
 
 	cr2 = readb(sport->port.membase + UARTCR2);
-	cr2 |= UARTCR2_RIE | UARTCR2_TIE | UARTCR2_RE | UARTCR2_TE;
+	cr2 |= UARTCR2_RIE | UARTCR2_RE | UARTCR2_TE;
 	writeb(cr2, sport->port.membase + UARTCR2);
 }
 
-- 
2.21.0