From owner-cvs-src@FreeBSD.ORG  Wed May 26 14:59:29 2004
Return-Path: <owner-cvs-src@FreeBSD.ORG>
Delivered-To: cvs-src@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP
	id 6461016A4CE; Wed, 26 May 2004 14:59:29 -0700 (PDT)
Received: from repoman.freebsd.org (repoman.freebsd.org [216.136.204.115])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id 5D84743D3F; Wed, 26 May 2004 14:59:29 -0700 (PDT)
	(envelope-from tmm@FreeBSD.org)
Received: from repoman.freebsd.org (localhost [127.0.0.1])
	by repoman.freebsd.org (8.12.11/8.12.11) with ESMTP id i4QLx1cI072335;
	Wed, 26 May 2004 14:59:01 -0700 (PDT)
	(envelope-from tmm@repoman.freebsd.org)
Received: (from tmm@localhost)
	by repoman.freebsd.org (8.12.11/8.12.11/Submit) id i4QLx1cQ072334;
	Wed, 26 May 2004 14:59:01 -0700 (PDT)
	(envelope-from tmm)
Message-Id: <200405262159.i4QLx1cQ072334@repoman.freebsd.org>
From: Thomas Moestl <tmm@FreeBSD.org>
Date: Wed, 26 May 2004 14:59:01 -0700 (PDT)
To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org,
	cvs-all@FreeBSD.org
X-FreeBSD-CVS-Branch: HEAD
Subject: cvs commit: src/sys/dev/uart uart_dev_ns8250.c
X-BeenThere: cvs-src@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: CVS commit messages for the src tree <cvs-src.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-src>,
	<mailto:cvs-src-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/cvs-src>
List-Post: <mailto:cvs-src@freebsd.org>
List-Help: <mailto:cvs-src-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-src>,
	<mailto:cvs-src-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 26 May 2004 21:59:29 -0000

tmm         2004/05/26 14:59:01 PDT

  FreeBSD src repository

  Modified files:
    sys/dev/uart         uart_dev_ns8250.c 
  Log:
  It seems that clearing the MCR_IE bit in the modem control register
  does not reliably prevent the triggering of interrupts for all supported
  configurations. Thus, the FIFO size probe could cause an interrupt,
  which could lead to an interrupt storm in the shared interrupt case.
  
  To prevent this, change ns8250_bus_probe() to use the overflow bit in
  the line status register instead of the RX ready bit in the interrupt
  identification register to detect whether the FIFO has filled up.
  This allows us to clear all bits in the interrupt enable register during
  the probe, which should prevent interrupts reliably.
  Additionally, the detected FIFO size may be a bit more accurate, because
  the overflow bit is only set when the FIFO did actually fill up, while
  interrupts would trigger a bit early.
  
  Reviewed and tested on a lot of hardware by:    marcel
  
  Revision  Changes    Path
  1.7       +23 -22    src/sys/dev/uart/uart_dev_ns8250.c