linux-kernel - Re: [PATCH v2] serial: 8250_dw: support high baudrates if possible

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Date:	Thu, 10 Jul 2014 22:11:58 -0500
From:	Alex Elder <elder@...aro.org>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	heikki.krogerus@...ux.intel.com, david.daney@...ium.com,
	loic.poulain@...el.com, linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] serial: 8250_dw: support high baudrates if possible

On 07/10/2014 06:13 PM, Greg KH wrote:
> On Tue, Jul 01, 2014 at 10:15:34AM -0500, Alex Elder wrote:
>> Currently the Synopsys DesignWare 8250 driver assumes its UART clock
>> runs at a fixed rate.  If a "real" clock was set up using the common
>> clock framework, and that clock's rate is adjustable, it may be
>> possible to support a wider range of baud rates by changing the
>> UART clock rate.
>>
>> This is done by setting up a uart_port->set_termios method that
>> requests a clock rate change if a different rate might make it
>> more likely to achieve a specified baud.  A new function
>> dw8250_adjustable_clk() determines whether such clock rate
>> adjustment is an option.
>>
>> Signed-off-by: Alex Elder <elder@...aro.org>
>> ---
>> v2: Limit clock changing to specific compatible devices.
>>
>>  drivers/tty/serial/8250/8250_dw.c | 57 +++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 57 insertions(+)
> 
> This no longer applies due to other changes in this driver.  Can you
> please refresh it against my tty-next branch of the tty.git tree and
> resend?

Interesting.  Heikki seems to have generalized
byt_set_termios() into dw8250_set_termios(), such
that it's almost the same as what I did.

I think I can just reuse it and simplify my patch
considerably.  But I'll do that in the morning...

					-Alex


> thanks,
> 
> greg k-h
> 

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