From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tobias Arp <tobiasarp@gmx.de>
Subject: Re: ST16C654 stoppes transmitting after a while
Date: Wed, 18 Jul 2012 13:16:23 +0200
Message-ID: <50069B07.80804@gmx.de>
References: <20120717074355.80180@gmx.net> <20120717105229.17b578a5@pyramind.ukuu.org.uk> <20120717100521.219440@gmx.net> <20120717122140.075aa7ae@pyramind.ukuu.org.uk> <20120717113603.9830@gmx.net> <20120717173847.1c5b4863@pyramind.ukuu.org.uk> <20120718063704.130240@gmx.net> <20120718074530.17620@gmx.net> <20120718120842.6bdc0fd8@pyramind.ukuu.org.uk>
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To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: linux-serial@vger.kernel.org

On Wed, 18 Jul 2012 09:45:30 +0200 "Tobias Arp" <tobiasarp@gmx.de> wrote:
>> The problem occurs very quick by setting the baud rate to 230400 on a single null modem connection (without usunign the orher ports of the quad uart). So i would say you are right with your guess...
>>> magic: 0x5401
>>> name: ttyS0
>>> flags: 0x00000A00
>>> count: 1
>>> stopped: 0
>>> hw_stopped: 1
>>> flow_stopped: 0
>>> packet: 0
>>> low_latency: 0
>>> warned: 0
>>> ctrl_status: 0x00
>>> receive_room: 4095
> Ok that's not quite what I had expected to see
>
> So the port is in use, not stopped at the higher levels and has lots of
> receiver room as expected.
>
> The hw_stopped flag is the hardware state - so somehow we've missed a
> transition on the flow control or the UART hasn't bothered reporting it
> or the IRQ got lost.
>
> When it jams transmitting does it unjam if you send a single character
> the other way ?
>
> Alan
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No it doesn't unjam be sending a single character from the remote side. 
It only unjams after plug out and plugin the
null modem cable (so an IRQ is generated caused by the DCD change or CTS 
change while replugin the cable).