From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 5 Oct 2002 10:53:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 5 Oct 2002 10:53:10 -0400 Received: from 62-190-217-225.pdu.pipex.net ([62.190.217.225]:53508 "EHLO darkstar.example.net") by vger.kernel.org with ESMTP id ; Sat, 5 Oct 2002 10:53:07 -0400 Date: Sat, 5 Oct 2002 16:06:45 +0100 From: jbradford@dial.pipex.com Message-Id: <200210051506.g95F6jfL000423@darkstar.example.net> To: linux-kernel@vger.kernel.org Subject: 2.5.x and 8250 UART problems Cc: rmk@arm.linux.org.uk Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org I've noticed that 8250 UART based serial port performance is poorer in 2.5.x than 2.4.x and 2.2.x, on a couple of my machines. The 486 SX-20 with 4 MB RAM, running 2.2.21 reliably achieves about 650 BPS download from another machine, with the port runnnig at 9600 bps. With 2.5.40, many characters are lost at 9600, making, e.g. a ZModem transfer retry for almost every block. A 486 SX-25 with 8 MB RAM, running 2.4.19 manages about 950 BPS reliably with the port set at 9600 bps. With 2.5.40, there are again a lot of lost characters. I know these are ancient machines, with rediculously low amounts of memory, but surely 9600 bps should be reliable, even if performance drops to 600-700 BPS, or even lower. I originally thought that the new kernel was using up memory that was previously available to be used as a buffer, and that extra hard disk access was causing the lost characters, but this doesn't seem to be the case. Any idea what's causing this? I can send more info and do more tests as required. John.