Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751992Ab0BZFgN (ORCPT ); Fri, 26 Feb 2010 00:36:13 -0500 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:47301 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751587Ab0BZFgL (ORCPT ); Fri, 26 Feb 2010 00:36:11 -0500 Subject: Re: USB mass storage and ARM cache coherency From: James Bottomley To: Benjamin Herrenschmidt Cc: Oliver Neukum , Catalin Marinas , Matthew Dharm , Russell King - ARM Linux , Greg KH , "Mankad, Maulik Ojas" , Sergei Shtylyov , Sebastian Siewior , linux-usb@vger.kernel.org, linux-kernel , "Shilimkar, Santosh" , Pavel Machek , Ming Lei , linux-arm-kernel In-Reply-To: <1267045954.23523.1692.camel@pasglop> References: <1266445892.16346.306.camel@pasglop> <201002192153.22159.oliver@neukum.org> <1266979689.23523.1669.camel@pasglop> <201002240816.10178.oliver@neukum.org> <1267045954.23523.1692.camel@pasglop> Content-Type: text/plain; charset="UTF-8" Date: Thu, 25 Feb 2010 12:36:25 +0000 Message-ID: <1267101385.2902.8.camel@mulgrave.site> Mime-Version: 1.0 X-Mailer: Evolution 2.28.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1282 Lines: 31 On Thu, 2010-02-25 at 08:12 +1100, Benjamin Herrenschmidt wrote: > On Wed, 2010-02-24 at 08:16 +0100, Oliver Neukum wrote: > > I don't know. The issue seems quite complex. It would seem better to > > centralize it as far as practical. Do you have a wrapper drivers could > > call? > > flush_dcache_page() ? :-) Actually, that can be wrong depending on the implementation. The problem is incoherency of the kernel page (dirty) with respect to user space aliases (clean). What has to happen on parisc is that the kernel alias needs flushing. We can guarantee the userspace aliases to be clean (and not moved in). We wouldn't want to incur the expense of flushing the user space pages as well. > Now, the subsystem might be the one to know whether something is mapped > into userspace or not (v4l in our case) in which case a wrapper could be > created. Right, so it's the responsibility of the API used by the subsystem. Thus Caitlin's pio_kmap seems the right one ... I don't understand what the additional problems are. James -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/