From owner-freebsd-current@FreeBSD.ORG  Sat Nov  8 16:25:03 2008
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 4CD28106564A;
	Sat,  8 Nov 2008 16:25:03 +0000 (UTC)
	(envelope-from hselasky@c2i.net)
Received: from swip.net (mailfe05.swip.net [212.247.154.129])
	by mx1.freebsd.org (Postfix) with ESMTP id AC9608FC0C;
	Sat,  8 Nov 2008 16:25:02 +0000 (UTC)
	(envelope-from hselasky@c2i.net)
X-Cloudmark-Score: 0.000000 []
X-Cloudmark-Analysis: v=1.0 c=1 a=dHLmn-RhnaEA:10 a=d4Qm339WgMUA:10
	a=d6BVkb5LuPPVEe4iNQMLyA==:17 a=W7yW5RWIGnIUdAu0NoAA:9
	a=t7RMLOW7sXuN4nJvu2FY-nvfdNEA:4 a=LY0hPdMaydYA:10
Received: from [62.113.135.6] (account mc467741@c2i.net [62.113.135.6]
	verified) by mailfe05.swip.net (CommuniGate Pro SMTP 5.2.6)
	with ESMTPA id 1042886932; Sat, 08 Nov 2008 17:25:01 +0100
From: Hans Petter Selasky <hselasky@c2i.net>
To: freebsd-current@freebsd.org
Date: Sat, 8 Nov 2008 17:27:06 +0100
User-Agent: KMail/1.9.7
References: <20081107082740.GA1334@icarus.home.lan>
	<200811081023.10058.hselasky@freebsd.org>
	<200811081353.09697.hselasky@c2i.net>
In-Reply-To: <200811081353.09697.hselasky@c2i.net>
MIME-Version: 1.0
Content-Type: text/plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
Message-Id: <200811081727.08788.hselasky@c2i.net>
Cc: freebsd-usb@freebsd.org
Subject: Re: (FWD) Serious busdma bug in -current in relation to USB harware.
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>, 
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sat, 08 Nov 2008 16:25:03 -0000

On Saturday 08 November 2008, Hans Petter Selasky wrote:
> On Saturday 08 November 2008, Alexander Motin wrote:

> What is the real reason to do that? If you are saying that you uses
> 1-byte alignment then you should be able to accept _any_ address that
> busdma will allocate to you! Why original data alignment should so
> strictly affect hardware operation?

Hi,

The real reason is that the EHCI and OHCI only takes the full physical address 
of the _first_ page, and then for the subsequent pages only stores the upper 
bits of the physical address, leaving it impossible to program a per-page 
data start offset. The hardware assumes that the lower part of the physical 
address wraps modulo PAGE_SIZE, and that's it. Don't ask me why they designed 
it like that. Currently USB is broken on all architectures where bouncing is 
used. I see no other way around this than to change busdma.

--HPS