Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758259Ab0BXVul (ORCPT ); Wed, 24 Feb 2010 16:50:41 -0500 Received: from iolanthe.rowland.org ([192.131.102.54]:59641 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1758203Ab0BXVuj (ORCPT ); Wed, 24 Feb 2010 16:50:39 -0500 Date: Wed, 24 Feb 2010 16:50:38 -0500 (EST) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Benjamin Herrenschmidt cc: Catalin Marinas , Matthew Dharm , , Russell King - ARM Linux , "Mankad,Maulik Ojas" , Sergei Shtylyov , Ming Lei , Sebastian Siewior , Oliver Neukum , linux-kernel , "Shilimkar,Santosh" , Pavel Machek , Greg KH , linux-arm-kernel , James Bottomley Subject: Re: USB mass storage and ARM cache coherency In-Reply-To: <1267046036.23523.1693.camel@pasglop> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1284 Lines: 30 On Thu, 25 Feb 2010, Benjamin Herrenschmidt wrote: > I'm surprised that usb-storage has an issue here. It shouldn't afaik, > since it's just a SCSI driver (or not anymore ?) It still is. There's also the ub driver, which is a non-SCSI block device driver for some of the same devices handled by usb-storage. > and the BIO or > filesystems handle things there no ? I haven't seen a single call to > flush_dcache_page() in any of drivers/scsi, drivers/ata or drivers/ide > when I looked... There is no real issue; it's just that the problem was first noted in connection with usb-storage reading in executable pages, so Catalin's initial post was oriented toward modifying usb-storage. The main issue here is that the same host controller will use PIO sometimes and DMA sometimes, depending on the details of the transfer. The USB core didn't expect this and consequently we violated the rules for DMA mapping. The question is: If the core is fixed so that the rules aren't violated, will everything work correctly? Alan Stern -- 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/