[PATCH] tty: serial: 8250_mtk: Fix quot calculation

[Matthias Brugger]

The calculation of value quot for highspeed register set to three
was wrong. This patch fixes the calculation so that the serial port
for baudrates bigger then 576000 baud is working correctly.

Signed-off-by: Matthias Brugger <***@gmail.com>
---
drivers/tty/serial/8250/8250_mtk.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
index 1c4b4bf..4376c48 100644
--- a/drivers/tty/serial/8250/8250_mtk.c
+++ b/drivers/tty/serial/8250/8250_mtk.c
@@ -81,7 +81,7 @@ mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
/* Set to highest baudrate supported */
if (baud >= 1152000)
baud = 921600;
- quot = DIV_ROUND_CLOSEST(port->uartclk, 256 * baud);
+ quot = (port->uartclk / (256 * baud)) + 1;
}

/*

[Matthias Brugger]

Hi Greg,

Post by Matthias Brugger
The calculation of value quot for highspeed register set to three
was wrong. This patch fixes the calculation so that the serial port
for baudrates bigger then 576000 baud is working correctly.
---
drivers/tty/serial/8250/8250_mtk.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
index 1c4b4bf..4376c48 100644
--- a/drivers/tty/serial/8250/8250_mtk.c
+++ b/drivers/tty/serial/8250/8250_mtk.c
@@ -81,7 +81,7 @@ mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
/* Set to highest baudrate supported */
if (baud >= 1152000)
baud = 921600;
- quot = DIV_ROUND_CLOSEST(port->uartclk, 256 * baud);
+ quot = (port->uartclk / (256 * baud)) + 1;
}
/*

Has this always been incorrect, or was it caused by a specific patch?

It has always been incorrect :o

Should it go to the stable kernels? If so, how far back?

No need to go to the stable kernels. The driver is only in linux-next.

Any comments on that?

Thanks,
Matthias

Cheers,
Matthias Brugger

thanks,
greg k-h

--
motzblog.wordpress.com