Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 9 Jun 2002 03:15:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 9 Jun 2002 03:15:23 -0400 Received: from fachschaft.cup.uni-muenchen.de ([141.84.250.61]:12551 "EHLO fachschaft.cup.uni-muenchen.de") by vger.kernel.org with ESMTP id ; Sun, 9 Jun 2002 03:15:22 -0400 Message-Id: <200206090709.g5979UX14894@fachschaft.cup.uni-muenchen.de> Content-Type: text/plain; charset=US-ASCII From: Oliver Neukum To: "Albert D. Cahalan" Subject: Re: PCI DMA to small buffers on cache-incoherent arch Date: Sun, 9 Jun 2002 09:15:12 +0200 X-Mailer: KMail [version 1.3.1] Cc: davem@redhat.com (David S. Miller), linux-kernel@vger.kernel.org In-Reply-To: <200206090657.g596vQj403167@saturn.cs.uml.edu> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Am Sonntag, 9. Juni 2002 08:57 schrieb Albert D. Cahalan: > Oliver Neukum writes: > >> For memory --> device DMA: > >> > >> 1. write back all cache lines affected by the DMA > >> 2. start the DMA > >> 3. invalidate the above cache lines > > > > Why the third step ? That data should still > > be valid. > > I made a mistake, but perhaps it is a good one. > There is no need to invalidate the cache lines, > but I'd guess that commonly the data won't be > used again. Doing the invalidate would free up > some cache lines, meaning that the CPU would > have empty slots to use for other stuff. Then this should be made commonly available and could be used eg. on kfree. The choice of kicking the data out or not could then be made. Regards Oliver - 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/