Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751185AbWHPOmY (ORCPT ); Wed, 16 Aug 2006 10:42:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751186AbWHPOmY (ORCPT ); Wed, 16 Aug 2006 10:42:24 -0400 Received: from dtp.xs4all.nl ([80.126.206.180]:52448 "HELO abra2.bitwizard.nl") by vger.kernel.org with SMTP id S1751185AbWHPOmX (ORCPT ); Wed, 16 Aug 2006 10:42:23 -0400 Date: Wed, 16 Aug 2006 16:42:22 +0200 From: Erik Mouw To: Robert Hancock Cc: Raphael Hertzog , Linux Kernel ML Subject: Re: How to avoid serial port buffer overruns? Message-ID: <20060816144221.GO15015@harddisk-recovery.com> References: <44E32D19.3090405@shaw.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <44E32D19.3090405@shaw.ca> Organization: Harddisk-recovery.com User-Agent: Mutt/1.5.12-2006-07-14 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1391 Lines: 36 On Wed, Aug 16, 2006 at 08:35:05AM -0600, Robert Hancock wrote: > Raphael Hertzog wrote: > >(Please CC me when replying) > > > >Hello, > > > >While using Linux on low-end (semi-embedded) hardware (386 SX 40Mhz, 8Mb > >RAM), I discovered that Linux on that machine would suffer from serial > >port buffer overruns quite easily if I use a baudrate high enough (I start > >loosing bytes at >19200 bauds and I would like to make it reliable up to > >115 kbauds). I check if overruns are happening with > >/proc/tty/driver/serial ("oe" field). > > What kind of serial port are you using? If it's an unbuffered 8250-type > port, it will NEVER be reliable at higher baud rates. You want a 16550 > (or better) port. I've run a cable modem connection at 115k2 over a 16450 UART on a 386DX40 for years. The tricks were: - hdparm -u 1 /dev/hda - play with IRQ priorities in such a way that the serial port UART was handled first (there used to be a kernel module to accomplish that in old debian releases) Erik -- +-- Erik Mouw -- www.harddisk-recovery.com -- +31 70 370 12 90 -- | Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/