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

[Greg KH]

On Fri, Oct 10, 2014 at 10:10:45AM +0200, Matthias Brugger wrote:
> 2014-10-09 23:52 GMT+02:00 Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>:
> > On Thu, Oct 09, 2014 at 06:23:31PM +0200, Matthias Brugger wrote:
> >> 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@xxxxxxxxx>
> >> ---
> >>  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.

Well, it's in 3.18-rc1, so it should at least go into 3.18-final.  I'll
queue it up for that.

thanks,

greg k-h
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