From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936954AbYD1QzK (ORCPT ); Mon, 28 Apr 2008 12:55:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934912AbYD1Qyw (ORCPT ); Mon, 28 Apr 2008 12:54:52 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:49482 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935358AbYD1Qyv (ORCPT ); Mon, 28 Apr 2008 12:54:51 -0400 Date: Mon, 28 Apr 2008 18:53:52 +0200 From: Ingo Molnar To: Alan Cox Cc: Michael Buesch , Andi Kleen , linux-kernel , vojtech@suse.cz, muli@il.ibm.com, jdmason@kudzu.us, tglx@linutronix.de, mingo@redhat.com, jbarnes@virtuousgeek.org Subject: Re: [PATCH RFC] x86: Fix 64-bit DMA masks on VIA Message-ID: <20080428165352.GD18210@elte.hu> References: <200804232055.13102.mb@bu3sch.de> <87mynjgyg9.fsf@basil.nowhere.org> <200804241606.00883.mb@bu3sch.de> <20080424153240.33b5300c@the-village.bc.nu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080424153240.33b5300c@the-village.bc.nu> User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Alan Cox wrote: > > > > This untested patch is supposed to fix DMAing on some VIA > > > > boards. Currently the DMA subsystem returns an error, if the > > > > driver does tell that it supports a 64bit DMA mask. So the > > > > driver probing would fail in that case. > > > > > > The driver is broken then. It is supposed to retry with a small > > > mask on an error. Please fix the driver. > > > > I already added a workaround to the driver. Why do we need to > > workaround this in _every_ driver? (Note that _every_ driver > > supporting a 64bit mask is affected). Why not fix it in the DMA > > layer? > > Some hardware wants to know it can get a given DMA mask or failure. I > agree however that a "pci_prefer_64bit_dma(pdev)" function would be a > good patch for someone to submit tot he PCI layer code. yes, and i suspect Michael is correct in suggesting that the majority of drivers would use that interface and would let the PCI layer handle the probing/fallback details. (Jesse Cc:-ed) Ingo