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

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Date:	Mon, 20 Oct 2014 13:30:38 +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

Hi Greg,

2014-10-10 10:10 GMT+02:00 Matthias Brugger <matthias.bgg@...il.com>:
> 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.

Any comments on that?

Thanks,
Matthias

>
> Cheers,
> Matthias Brugger
>
>>
>> thanks,
>>
>> greg k-h
>
>
>
> --
> motzblog.wordpress.com



-- 
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