From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lee Howard Subject: Re: serial flow control appears broken Date: Thu, 26 Jul 2007 22:53:09 -0700 Message-ID: <46A98845.8010806@howardsilvan.com> References: <46A84B4A.6070902@shaw.ca> <46A8C6F1.4080309@howardsilvan.com> <20070726173121.70088a92@the-village.bc.nu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from gateway.howardsilvan.com ([64.146.212.27]:40058 "EHLO mail.howardsilvan.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753229AbXG0FyZ (ORCPT ); Fri, 27 Jul 2007 01:54:25 -0400 In-Reply-To: <20070726173121.70088a92@the-village.bc.nu> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Alan Cox Cc: Robert Hancock , linux-serial@vger.kernel.org, tytso@mit.edu, rmk@arm.linux.org.uk, linux-kernel@vger.kernel.org Alan Cox wrote: >>Serial: 8250/16550 driver $Revision: 1.90 $ 8 ports, IRQ sharing enabled >>ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A >>ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A >> >>It's a Shuttle HOT-661 motherboard (VIA Apollo Pro Plus mainboard >>chipset). Both FreeBSD and Linux identify the serial chipset type as >>16550A. >> >> > >So you've got 16bytes of buffering. That ought to be enough on a modern >PC. The older kernels use quite limited internal buffers which may be a >factor, the current ones have a rewritten tty buffering layer which may >improve matters enormously. > So, does this explain why I wouldn't have a problem at 115200 bps with kernel 2.2.5 but why I do with 2.6.5 and 2.6.18? Both hardware and software flow control work fine with 2.2.5 (meaning I don't see any error message and I don't have any data corruption), but neither works to avoid the "kernel: ttyS1: 1 input overrun(s)" and consequent data corruption issue in 2.6.5 nor 2.6.18. Was there some associated application change in tty handling that needed to occur between the 2.2 and 2.6 kernels to properly implement flow control? Thanks, Lee.