From owner-freebsd-arch@FreeBSD.ORG  Sun Oct 16 04:39:22 2011
Return-Path: <owner-freebsd-arch@FreeBSD.ORG>
Delivered-To: freebsd-arch@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id E37031065673
	for <freebsd-arch@freebsd.org>; Sun, 16 Oct 2011 04:39:22 +0000 (UTC)
	(envelope-from adrian.chadd@gmail.com)
Received: from mail-gx0-f182.google.com (mail-gx0-f182.google.com
	[209.85.161.182])
	by mx1.freebsd.org (Postfix) with ESMTP id A57998FC15
	for <freebsd-arch@freebsd.org>; Sun, 16 Oct 2011 04:39:22 +0000 (UTC)
Received: by ggeq3 with SMTP id q3so2797976gge.13
	for <freebsd-arch@freebsd.org>; Sat, 15 Oct 2011 21:39:22 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma;
	h=mime-version:sender:in-reply-to:references:date
	:x-google-sender-auth:message-id:subject:from:to:cc:content-type;
	bh=4ZL8JTi74pr3WC6DvMadhCV1rvuMoetmtX6UpbGVqK4=;
	b=YdB4fs142ZU4A5ssa+VFOIJK+eOPpWliHDPxkPuodk+IKtZToVFG90wmVlDlP9e6RN
	2BXQp7mDAxtm9Rcclen0Esp7sSpXJnqmBj59kwZ6cdihFvvPvF2Sk0LW6n/0tS0iNa1z
	9I2ftydHwgmHzglfISG8hhTx58Io7B451aHb8=
MIME-Version: 1.0
Received: by 10.236.170.168 with SMTP id p28mr10923088yhl.100.1318739961903;
	Sat, 15 Oct 2011 21:39:21 -0700 (PDT)
Sender: adrian.chadd@gmail.com
Received: by 10.236.95.147 with HTTP; Sat, 15 Oct 2011 21:39:21 -0700 (PDT)
In-Reply-To: <4EEA1F8B-9854-4C5C-A397-95AD454D3680@bsdimp.com>
References: <CAJ-VmonJnHyLQJ-kVtMV=X7mq7=wq2MGn9wUqdbEtZ6qXd52rg@mail.gmail.com>
	<4EEA1F8B-9854-4C5C-A397-95AD454D3680@bsdimp.com>
Date: Sun, 16 Oct 2011 12:39:21 +0800
X-Google-Sender-Auth: DruQAVKIyTCx1is_KYPeJWSHTZM
Message-ID: <CAJ-VmonEAiosgJNLU75OFWzOk8CsshBOT_H7WcWKp+5VKFsRrA@mail.gmail.com>
From: Adrian Chadd <adrian@freebsd.org>
To: Warner Losh <imp@bsdimp.com>
Content-Type: text/plain; charset=ISO-8859-1
Cc: freebsd-arch@freebsd.org
Subject: Re: newbus bus access routines and bus_space_barrier()
X-BeenThere: freebsd-arch@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussion related to FreeBSD architecture <freebsd-arch.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-arch>,
	<mailto:freebsd-arch-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-arch>
List-Post: <mailto:freebsd-arch@freebsd.org>
List-Help: <mailto:freebsd-arch-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-arch>,
	<mailto:freebsd-arch-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sun, 16 Oct 2011 04:39:23 -0000

On 16 October 2011 11:45, Warner Losh <imp@bsdimp.com> wrote:
> Usually they are needed, but we get away without them often because they are needed in a limited set of circumstances and we have memory barriers in our locking primitives.

Right. I'll just change the ath driver register ops to enforce a
read/write barrier on each read or write.
It'd be nice to teach the driver and the HAL about "correct" barriers
but I just don't have the time. :(

(FYI: apparently linux's ioread32/iowrite32 operations enforce
barriers on each op.)



Adrian