From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754302Ab0CBX3a (ORCPT ); Tue, 2 Mar 2010 18:29:30 -0500 Received: from gate.crashing.org ([63.228.1.57]:51647 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754183Ab0CBX3U (ORCPT ); Tue, 2 Mar 2010 18:29:20 -0500 Subject: Re: USB mass storage and ARM cache coherency From: Benjamin Herrenschmidt To: FUJITA Tomonori Cc: James.Bottomley@HansenPartnership.com, linux@arm.linux.org.uk, catalin.marinas@arm.com, mdharm-kernel@one-eyed-alien.net, linux-usb@vger.kernel.org, x0082077@ti.com, sshtylyov@ru.mvista.com, tom.leiming@gmail.com, bigeasy@linutronix.de, oliver@neukum.org, linux-kernel@vger.kernel.org, santosh.shilimkar@ti.com, pavel@ucw.cz, greg@kroah.com, linux-arm-kernel@lists.infradead.org In-Reply-To: <20100302211049V.fujita.tomonori@lab.ntt.co.jp> References: <20100226210030.GC23933@n2100.arm.linux.org.uk> <1267316072.23523.1842.camel@pasglop> <1267333263.2762.11.camel@mulgrave.site> <20100302211049V.fujita.tomonori@lab.ntt.co.jp> Content-Type: text/plain; charset="UTF-8" Date: Wed, 03 Mar 2010 10:26:56 +1100 Message-ID: <1267572416.2173.22.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2010-03-02 at 21:11 +0900, FUJITA Tomonori wrote: > > > Sorry to be a bit late to the party (on holiday), but I/D coherency > is > > supposed to be taken care of using flush_cache_page in the memory > > mapping routines. > > powerpc does that? To be exact, powerpc doesn't need > flush_cache_page() and handles I/D coherency in the pte modification > code. powerpc uses PG_arch_1 to avoid unnecessarily handling I/D > coherency. Seems that IA64 does the same trick with PG_arch_1. Right. We set PG_arch_1 to avoid doing it again of a given physical page. We assume that it's always cleared when a page is recycled by the page cache and we also clear it in flush_dcache_page() though the need for that later thing is dubious... Cheers, Ben.