tty/serial: atmel: fix fractional baud rate computation
The problem with previous code was it rounded values in wrong
place and produced wrong baud rate in some cases.
Signed-off-by: Alexey Starikovskiy <aystarik@gmail.com>
[nicolas.ferre@atmel.com: port to newer kernel and add commit log]
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 5f550d9f..fd8aa1f 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -2170,13 +2170,15 @@
* accurately. This feature is enabled only when using normal mode.
* baudrate = selected clock / (8 * (2 - OVER) * (CD + FP / 8))
* Currently, OVER is always set to 0 so we get
- * baudrate = selected clock (16 * (CD + FP / 8))
+ * baudrate = selected clock / (16 * (CD + FP / 8))
+ * then
+ * 8 CD + FP = selected clock / (2 * baudrate)
*/
if (atmel_port->has_frac_baudrate &&
(mode & ATMEL_US_USMODE) == ATMEL_US_USMODE_NORMAL) {
- div = DIV_ROUND_CLOSEST(port->uartclk, baud);
- cd = div / 16;
- fp = DIV_ROUND_CLOSEST(div % 16, 2);
+ div = DIV_ROUND_CLOSEST(port->uartclk, baud * 2);
+ cd = div >> 3;
+ fp = div & ATMEL_US_FP_MASK;
} else {
cd = uart_get_divisor(port, baud);
}