linux-kernel - [PATCH] tty/serial: atmel: fix out of range clock divider handling

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Message-Id: <20191211162954.8393-1-david.engraf@sysgo.com>
Date:   Wed, 11 Dec 2019 17:29:54 +0100
From:   David Engraf <david.engraf@...go.com>
To:     richard.genoud@...il.com, gregkh@...uxfoundation.org,
        jslaby@...e.com, nicolas.ferre@...rochip.com,
        alexandre.belloni@...tlin.com, ludovic.desroches@...rochip.com
Cc:     linux-serial@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, David Engraf <david.engraf@...go.com>
Subject: [PATCH] tty/serial: atmel: fix out of range clock divider handling

Use MCK_DIV8 when the clock divider is > 65535. Unfortunately the mode
register was already written thus the clock selection is ignored.

Fix by writing the mode register after calculating the baudrate.

Signed-off-by: David Engraf <david.engraf@...go.com>
---
 drivers/tty/serial/atmel_serial.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index a8dc8af83f39..9983e2fabbac 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -2270,9 +2270,6 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
 		mode |= ATMEL_US_USMODE_NORMAL;
 	}
 
-	/* set the mode, clock divisor, parity, stop bits and data size */
-	atmel_uart_writel(port, ATMEL_US_MR, mode);
-
 	/*
 	 * when switching the mode, set the RTS line state according to the
 	 * new mode, otherwise keep the former state
@@ -2315,6 +2312,9 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
 	}
 	quot = cd | fp << ATMEL_US_FP_OFFSET;
 
+	/* set the mode, clock divisor, parity, stop bits and data size */
+	atmel_uart_writel(port, ATMEL_US_MR, mode);
+
 	if (!(port->iso7816.flags & SER_ISO7816_ENABLED))
 		atmel_uart_writel(port, ATMEL_US_BRGR, quot);
 	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
-- 
2.17.1