From: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Date: Mon, 20 Mar 2017 09:05:38 +0000 (+0100)
Subject: serial: mxs-auart: Fix baudrate calculation
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=a6040bc610554c66088fda3608ae5d6307c548e4;p=openwrt%2Fstaging%2Fblogic.git

serial: mxs-auart: Fix baudrate calculation

The reference manual for the i.MX28 recommends to calculate the divisor
as

	divisor = (UARTCLK * 32) / baud rate, rounded to the nearest integer

, so let's do this. For a typical setup of UARTCLK = 24 MHz and baud
rate = 115200 this changes the divisor from 6666 to 6667 and so the
actual baud rate improves from 115211.521 Bd (error ≅ 0.01 %) to
115194.240 Bd (error ≅ 0.005 %).

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
index 6989b227d134..be94246b6fcc 100644
--- a/drivers/tty/serial/mxs-auart.c
+++ b/drivers/tty/serial/mxs-auart.c
@@ -1088,7 +1088,7 @@ static void mxs_auart_settermios(struct uart_port *u,
 					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;
+		div = DIV_ROUND_CLOSEST(u->uartclk * 32, baud);
 	}
 
 	ctrl |= AUART_LINECTRL_BAUD_DIVFRAC(div & 0x3F);