From owner-svn-src-head@FreeBSD.ORG  Fri May 15 05:37:37 2009
Return-Path: <owner-svn-src-head@FreeBSD.ORG>
Delivered-To: svn-src-head@FreeBSD.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 3FE5C106566C;
	Fri, 15 May 2009 05:37:37 +0000 (UTC) (envelope-from imp@bsdimp.com)
Received: from harmony.bsdimp.com (bsdimp.com [199.45.160.85])
	by mx1.freebsd.org (Postfix) with ESMTP id F40618FC26;
	Fri, 15 May 2009 05:37:36 +0000 (UTC) (envelope-from imp@bsdimp.com)
Received: from localhost (localhost [127.0.0.1])
	by harmony.bsdimp.com (8.14.3/8.14.1) with ESMTP id n4F5ZSBh057956;
	Thu, 14 May 2009 23:35:28 -0600 (MDT) (envelope-from imp@bsdimp.com)
Date: Thu, 14 May 2009 23:35:36 -0600 (MDT)
Message-Id: <20090514.233536.1299798630.imp@bsdimp.com>
To: stas@FreeBSD.org
From: "M. Warner Losh" <imp@bsdimp.com>
In-Reply-To: <20090515092205.6f6d06fa.stas@FreeBSD.org>
References: <200905122114.n4CLEag9033208@svn.freebsd.org>
	<20090514.213712.-404854369.imp@bsdimp.com>
	<20090515092205.6f6d06fa.stas@FreeBSD.org>
X-Mailer: Mew version 5.2 on Emacs 21.3 / Mule 5.0 (SAKAKI)
Mime-Version: 1.0
Content-Type: Text/Plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org,
	src-committers@FreeBSD.org
Subject: Re: svn commit: r192027 - head/sys/arm/at91
X-BeenThere: svn-src-head@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: SVN commit messages for the src tree for head/-current
	<svn-src-head.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-head>,
	<mailto:svn-src-head-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/svn-src-head>
List-Post: <mailto:svn-src-head@freebsd.org>
List-Help: <mailto:svn-src-head-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-head>,
	<mailto:svn-src-head-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Fri, 15 May 2009 05:37:37 -0000

In message: <20090515092205.6f6d06fa.stas@FreeBSD.org>
            Stanislav Sedov <stas@FreeBSD.org> writes:
: On Thu, 14 May 2009 21:37:12 -0600 (MDT)
: "M. Warner Losh" <imp@bsdimp.com> mentioned:
: 
: > In message: <200905122114.n4CLEag9033208@svn.freebsd.org>
: >             Stanislav Sedov <stas@FreeBSD.org> writes:
: > : @@ -926,6 +937,7 @@ atestart_locked(struct ifnet *ifp)
: > :  		 * tell the hardware to xmit the packet.
: > :  		 */
: > :  		WR4(sc, ETH_TAR, segs[0].ds_addr);
: > : +		BARRIER(sc, ETH_TAR, 8, BUS_SPACE_BARRIER_WRITE);
: > :  		WR4(sc, ETH_TCR, segs[0].ds_len);
: > 
: > Why is a barrier needed here?
: > 
: Writing the TCR register triggers the transmit, so it had to be written
: strongly after the TAR register. That's why I added the barrier here.

Then shouldn't the barrier be after TCR write?  Or does this ensure
that the write is before TCR?

Warner