linux-kernel - Re: [PATCH] tty: serial: 8250: remove U6715 16550A auto-detection

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Message-ID: <514AC6AA.6050102@st.com>
Date:	Thu, 21 Mar 2013 09:36:58 +0100
From:	Philippe LANGLAIS <philippe.langlais@...com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	Hans-Peter Oeri <hp@...i.ch>,
	"heikki.krogerus@...ux.intel.com" <heikki.krogerus@...ux.intel.com>
Subject: Re: [PATCH] tty: serial: 8250: remove U6715 16550A auto-detection


On 03/20/2013 06:21 PM, Greg Kroah-Hartman wrote:
> On Tue, Mar 19, 2013 at 08:50:09PM +0100, Philippe Langlais wrote:
>> The auto-detection based on 64 bytes fifo size causes troubles
>> for the identification of the MultiTechZPX Modems (pci 11c1:0480).
>> They loose the ability to do hardware flow control
>> (specifically CTS is never set).
>>
>> Signed-off-by: Philippe Langlais <philippe.langlais@...com>
>> ---
>>   drivers/tty/serial/8250/8250.c |    9 ---------
>>   1 file changed, 9 deletions(-)
>>
>> diff --git a/drivers/tty/serial/8250/8250.c b/drivers/tty/serial/8250/8250.c
>> index cf6a538..3255014 100644
>> --- a/drivers/tty/serial/8250/8250.c
>> +++ b/drivers/tty/serial/8250/8250.c
>> @@ -1026,15 +1026,6 @@ static void autoconfig_16550a(struct uart_8250_port *up)
>>   
>>   		return;
>>   	}
>> -
>> -	/*
>> -	 * We distinguish between 16550A and U6 16550A by counting
>> -	 * how many bytes are in the FIFO.
>> -	 */
>> -	if (up->port.type == PORT_16550A && size_fifo(up) == 64) {
>> -		up->port.type = PORT_U6_16550A;
>> -		up->capabilities |= UART_CAP_AFE;
>> -	}
> So you just broke this functionality for all of the other devices it
> does work properly for?  That's not nice, and not acceptable.
Yes, I know, but as U6715 & U6XXX kernel maintainer there is no risk to 
do that,
kernel for such platforms are not managed in mainstream, there are more 
risks
to keep these lines for other platforms.
>
> Please fix this properly.
I don't know how to distinguish MultiTechZPX Modems, so I rather to 
remove these lines.
>
> greg k-h
Philippe--
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