From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Hurley Subject: Re: Broken serial port Date: Tue, 17 Jun 2014 15:28:02 -0400 Message-ID: <53A096C2.7060800@hurleysoftware.com> References: <53A08D64.1060800@Vivier.EU> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <53A08D64.1060800@Vivier.EU> Sender: linux-kernel-owner@vger.kernel.org To: Laurent Vivier Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Jiri Slaby , Greg Kroah-Hartman , Seth Bollinger List-Id: linux-serial@vger.kernel.org On 06/17/2014 02:48 PM, Laurent Vivier wrote: > Hi, > > I'm not subscribed to these mailing lists, so CC: me. > > I'm playing for some days with a kernel 3.15 on an old mac performa 575 > and it seems that the serial port is broken. When I log on using the > console on the serial port it seems there is an screen refresh added > after each character I send. What uart driver is this happening on? This is a known bug being worked on for these uart drivers: sunsab sunzilog ip22zilog pmac_zilog Regards, Peter Hurley > A little demo : > > http://asciinema.org/a/10211 [at 3:20] > > I bisect and I found this commit : > > commit 717f3bbab3c7628736ef738fdbf3d9a28578c26c > Author: Seth Bollinger > Date: Tue Mar 25 12:55:37 2014 -0500 > > serial_core: Fix conditional start_tx on ring buffer not empty > > If the serial_core ring buffer empties just as the tty layer receives > an XOFF, then start_tx will never be called when the tty layer > receives an XON as the serial_core ring buffer is empty. This will > possibly leave a few bytes trapped in the fifo for drivers that > disable the transmitter when flow controlled. > > Signed-off-by: Seth Bollinger > Signed-off-by: Greg Kroah-Hartman > > > If I revert it, all works fine : > > http://asciinema.org/a/10212 > > Regards, > Laurent >