linux-kernel - [PATCH 3.16 109/178] serial: mxs-auart: fix baud rate range

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Date:   Sun, 16 Jul 2017 14:56:46 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Stefan Wahren" <stefan.wahren@...e.com>,
        "Fabio Estevam" <fabio.estevam@...escale.com>
Subject: [PATCH 3.16 109/178] serial: mxs-auart: fix baud rate range

3.16.46-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Stefan Wahren <stefan.wahren@...e.com>

commit df57cf6a879502cd6e5559c1f2d6db12128e074f upstream.

Currently mxs-auart doesn't care correctly about the baud rate divisor.
According to reference manual the baud rate divisor must be between
0x000000EC and 0x003FFFC0. So calculate the possible baud rate range
and use it for uart_get_baud_rate().

Signed-off-by: Stefan Wahren <stefan.wahren@...e.com>
Reviewed-by: Fabio Estevam <fabio.estevam@...escale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/tty/serial/mxs-auart.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/drivers/tty/serial/mxs-auart.c
+++ b/drivers/tty/serial/mxs-auart.c
@@ -90,6 +90,8 @@
 #define AUART_CTRL2_TXE				(1 << 8)
 #define AUART_CTRL2_UARTEN			(1 << 0)
 
+#define AUART_LINECTRL_BAUD_DIV_MAX		0x003fffc0
+#define AUART_LINECTRL_BAUD_DIV_MIN		0x000000ec
 #define AUART_LINECTRL_BAUD_DIVINT_SHIFT	16
 #define AUART_LINECTRL_BAUD_DIVINT_MASK		0xffff0000
 #define AUART_LINECTRL_BAUD_DIVINT(v)		(((v) & 0xffff) << 16)
@@ -566,7 +568,7 @@ static void mxs_auart_settermios(struct
 {
 	struct mxs_auart_port *s = to_auart_port(u);
 	u32 bm, ctrl, ctrl2, div;
-	unsigned int cflag, baud;
+	unsigned int cflag, baud, baud_min, baud_max;
 
 	cflag = termios->c_cflag;
 
@@ -656,7 +658,9 @@ static void mxs_auart_settermios(struct
 	}
 
 	/* set baud rate */
-	baud = uart_get_baud_rate(u, termios, old, 0, u->uartclk);
+	baud_min = DIV_ROUND_UP(u->uartclk * 32, AUART_LINECTRL_BAUD_DIV_MAX);
+	baud_max = u->uartclk * 32 / AUART_LINECTRL_BAUD_DIV_MIN;
+	baud = uart_get_baud_rate(u, termios, old, baud_min, baud_max);
 	div = u->uartclk * 32 / baud;
 	ctrl |= AUART_LINECTRL_BAUD_DIVFRAC(div & 0x3F);
 	ctrl |= AUART_LINECTRL_BAUD_DIVINT(div >> 6);