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 6989b227d1349baeb0cb05ed9f7cff8572e36324..be94246b6fcca1874161470035b9d9bd91237f88 100644 (file)
--- 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);