Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751232AbWHPX1o (ORCPT ); Wed, 16 Aug 2006 19:27:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751234AbWHPX1n (ORCPT ); Wed, 16 Aug 2006 19:27:43 -0400 Received: from mustang.oldcity.dca.net ([216.158.38.3]:49090 "HELO mustang.oldcity.dca.net") by vger.kernel.org with SMTP id S1751232AbWHPX1n (ORCPT ); Wed, 16 Aug 2006 19:27:43 -0400 Subject: Re: How to avoid serial port buffer overruns? From: Lee Revell To: Russell King Cc: Paul Fulghum , Raphael Hertzog , Linux Kernel ML In-Reply-To: <20060816231926.GC12407@flint.arm.linux.org.uk> References: <20060816104559.GF4325@ouaza.com> <1155753868.3397.41.camel@mindpipe> <44E37095.9070200@microgate.com> <1155762739.7338.18.camel@mindpipe> <1155767066.2600.19.camel@localhost.localdomain> <20060816231033.GB12407@flint.arm.linux.org.uk> <1155770107.8796.14.camel@mindpipe> <20060816231926.GC12407@flint.arm.linux.org.uk> Content-Type: text/plain Date: Wed, 16 Aug 2006 19:28:19 -0400 Message-Id: <1155770899.8796.21.camel@mindpipe> Mime-Version: 1.0 X-Mailer: Evolution 2.6.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1369 Lines: 34 On Thu, 2006-08-17 at 00:19 +0100, Russell King wrote: > On Wed, Aug 16, 2006 at 07:15:06PM -0400, Lee Revell wrote: > > On Thu, 2006-08-17 at 00:10 +0100, Russell King wrote: > > > MIDI uses its own driver - sound/drivers/serial-u16550.c. My guess > > > is there's something in the system starving interrupt servicing. > > > Serial is very sensitive to that, and increases in other system > > > latencies tends to have an adverse impact on serial. > > > > Have you seen many other reports of serial working reliably in 2.4 but > > not in 2.6? Right now this is the only clue I have to go on... > > There have been one or two, but the above is basically as far as I've > got. Unfortunately, I don't have any machines slow enough (or maybe > with the right hardware) to exhibit the problem. > OK, thanks. FWIW here is the serial board we are using: http://www.moschip.com/html/MCS9845.html The hardware guy says "The mn9845cv, have in default 2 serial ports and one ISA bus, where we have connected the tl16c554, quad serial port." Hopefully Ingo's latency tracer can tell me what is holding off interrupts. Lee - 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/