linux-kernel - Re: [PATCH] tty: serial: 8250

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Date:	Fri, 10 Oct 2014 10:10:45 +0200
From:	Matthias Brugger <matthias.bgg@...il.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	jslaby@...e.cz, Heiko Stübner <heiko@...ech.de>,
	Yingjoe Chen <yingjoe.chen@...il.com>,
	Howard Chen <ibanezchen@...il.com>,
	linux-serial@...r.kernel.org
Subject: Re: [PATCH] tty: serial: 8250_mtk: Fix quot calculation

2014-10-09 23:52 GMT+02:00 Greg KH <gregkh@...uxfoundation.org>:
> 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@...il.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;
>>       }
>>
>>       /*
>
> 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.

Cheers,
Matthias Brugger

>
> thanks,
>
> greg k-h



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