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

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

[Matthias Brugger]

From: Matthias Brugger <matthias.bgg@gmail.com>

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 <matthias.bgg@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 8f37d57..de7aae5 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;
 	}
 
 	/*
-- 
1.9.1

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

[Arnd Bergmann]

On Friday 31 October 2014 17:36:35 Matthias Brugger wrote:
> -               quot = DIV_ROUND_CLOSEST(port->uartclk, 256 * baud);
> +               quot = (port->uartclk / (256 * baud)) + 1;

Should this be DIV_ROUND_UP then?

	Arnd

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

[eddie huang]

On Fri, 2014-10-31 at 17:48 +0100, Arnd Bergmann wrote:
> On Friday 31 October 2014 17:36:35 Matthias Brugger wrote:
> > -               quot = DIV_ROUND_CLOSEST(port->uartclk, 256 * baud);
> > +               quot = (port->uartclk / (256 * baud)) + 1;
> 
> Should this be DIV_ROUND_UP then?
> 
> 	Arnd
> 

I think DIV_ROUND_UP is more suitable in this case, and I already do
this and test OK on my MTK platform

http://lists.infradead.org/pipermail/linux-arm-kernel/2014-October/296149.html