From owner-freebsd-mips@FreeBSD.ORG  Sat Oct  5 17:18:51 2013
Return-Path: <owner-freebsd-mips@FreeBSD.ORG>
Delivered-To: freebsd-mips@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTP id 52069D39
 for <freebsd-mips@freebsd.org>; Sat,  5 Oct 2013 17:18:51 +0000 (UTC)
 (envelope-from adrian.chadd@gmail.com)
Received: from mail-pb0-x236.google.com (mail-pb0-x236.google.com
 [IPv6:2607:f8b0:400e:c01::236])
 (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits))
 (No client certificate requested)
 by mx1.freebsd.org (Postfix) with ESMTPS id 2C3A62C25
 for <freebsd-mips@freebsd.org>; Sat,  5 Oct 2013 17:18:51 +0000 (UTC)
Received: by mail-pb0-f54.google.com with SMTP id ro12so5315923pbb.13
 for <freebsd-mips@freebsd.org>; Sat, 05 Oct 2013 10:18:50 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113;
 h=mime-version:sender:date:message-id:subject:from:to:content-type;
 bh=KV9PKgf3fohsZbVCb1nCjX6H2z4/ZNCF1ueqSXNyM6g=;
 b=wKnXp07vDrw5VAGtuV/8Aag+BbpQZlYdb1pNU114OSeqMr1FZcBg8qdahgvgwLaUmO
 o9u6hkN3Kd8l6ExguDCyxyWSVD22peLaLuqU1fqz35QEL1eCaGpwIHzmO9DocE4IDuH8
 vBKxKcnj55hX5Z6fijgaJUc03gs97CVo6Yz1PV240RYVyUywd5ZDI+wFnped9Ez73zYr
 25xl94vaiFum+tBzAZW2VVfoQsXcfOzzRrYfMEaMqeMQxoBWAyYUpalHSCsJmZMUzT59
 Tfpb/1/rtxvDwiY3fTQ8ZyNxrNZhPmszbkDPOAFn3jAexH679Z9qOGno417EY2Mc+jyQ
 8ahg==
MIME-Version: 1.0
X-Received: by 10.68.52.170 with SMTP id u10mr21159502pbo.34.1380993530555;
 Sat, 05 Oct 2013 10:18:50 -0700 (PDT)
Sender: adrian.chadd@gmail.com
Received: by 10.70.42.10 with HTTP; Sat, 5 Oct 2013 10:18:50 -0700 (PDT)
Date: Sat, 5 Oct 2013 10:18:50 -0700
X-Google-Sender-Auth: esd-vnBp3v1QkeHQLw41lGtWTUc
Message-ID: <CAJ-Vmo=PNSsW0eEAhc9LEDLswsj41VN+FX1vakQL=qGGdKqMuw@mail.gmail.com>
Subject: How's bus-space stuff supposed to work with superscalar MIPS?
From: Adrian Chadd <adrian@freebsd.org>
To: "freebsd-mips@freebsd.org" <freebsd-mips@freebsd.org>
Content-Type: text/plain; charset=ISO-8859-1
X-Content-Filtered-By: Mailman/MimeDel 2.1.14
X-BeenThere: freebsd-mips@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
List-Id: Porting FreeBSD to MIPS <freebsd-mips.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-mips>,
 <mailto:freebsd-mips-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-mips>
List-Post: <mailto:freebsd-mips@freebsd.org>
List-Help: <mailto:freebsd-mips-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-mips>,
 <mailto:freebsd-mips-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sat, 05 Oct 2013 17:18:51 -0000

Hi all,

I've been bringing up the AR9344 PHY and after a lot of digging, I
discovered that I can fix things by changing ARGE_WRITE() (ie, write to the
ethernet space registers) to:

bus_write_4();
bus_read_4();

.. to (what I'm guessing here) flush the write out before the next
instruction is run.

So, given this particular hilarity has shown up, what's the story with
doing IO accesses on a superscalar MIPS CPU? If it's going to kseg1, is it
somehow going to magically enforce ordering? Or am I right in thinking we
will need explicit barriers here?

I'd like to sneak this into the initial mips74k bringup support that I'm
going to commit to -HEAD soon.

Thanks,


-adrian