Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756996AbYFWKjj (ORCPT ); Mon, 23 Jun 2008 06:39:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754685AbYFWKja (ORCPT ); Mon, 23 Jun 2008 06:39:30 -0400 Received: from gate.crashing.org ([63.228.1.57]:59052 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750942AbYFWKja (ORCPT ); Mon, 23 Jun 2008 06:39:30 -0400 Subject: Re: sata_svw data corruption, strange problems From: Benjamin Herrenschmidt Reply-To: benh@kernel.crashing.org To: Alan Cox Cc: Tejun Heo , Pavel Machek , Andreas Schwab , kernel list , jgarzik@pobox.com, IDE/ATA development list , Trivial patch monkey In-Reply-To: <20080623104221.3b4fb350@lxorguk.ukuu.org.uk> References: <20080617093602.GA28140@elf.ucw.cz> <485EF061.3010601@kernel.org> <20080623082055.GB1850@elf.ucw.cz> <20080623085338.GE1850@elf.ucw.cz> <485F6540.6000907@kernel.org> <20080623090130.GF1850@elf.ucw.cz> <1214211859.8011.250.camel@pasglop> <485F7184.1030907@kernel.org> <20080623104221.3b4fb350@lxorguk.ukuu.org.uk> Content-Type: text/plain Date: Mon, 23 Jun 2008 20:23:22 +1000 Message-Id: <1214216602.8011.259.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.22.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1290 Lines: 32 On Mon, 2008-06-23 at 10:42 +0100, Alan Cox wrote: > > > BTW. Tejun, I suppose that usually starting DMA after issuing the > > > command is a standard practice of legacy/sff type controllers ? Or it's > > > just because that's how linux did it until now ? > > > > It's how the standard says it should be programmed. Please take a look > > at section 3 of the following document. > > > > http://www.centrillium-it.com/Projects/idems100.pdf > > > > It's a non-issue for PATA ones as the host is responsible for running > > It's very much an issue for PATA. If you start the DMA before time things > go wrong. The DMA has to start after the command is issued (or for ATAPI > after the command and the cdb are issued). Various ATAPI devices get > quite cross if you mess this up. > > In some cases the driver code also depends upon this as we software drive > the data clocks so have to reprogram them after command issue and before > data transfer begins. Might explain why those broadcom chipsets are also allergic to ATAPI DMA :-) Ben. -- 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/