Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756595AbYJJWpd (ORCPT ); Fri, 10 Oct 2008 18:45:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752455AbYJJWpX (ORCPT ); Fri, 10 Oct 2008 18:45:23 -0400 Received: from colo.lackof.org ([198.49.126.79]:49577 "EHLO colo.lackof.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751543AbYJJWpW (ORCPT ); Fri, 10 Oct 2008 18:45:22 -0400 Date: Fri, 10 Oct 2008 16:45:08 -0600 From: Grant Grundler To: FUJITA Tomonori Cc: yinghai@kernel.org, grundler@parisc-linux.org, matthew@wil.cx, jbarnes@virtuousgeek.org, mingo@elte.hu, tglx@linutronix.de, hpa@zytor.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org Subject: Re: [PATCH] pci: print out DMA mask info Message-ID: <20081010224508.GB28369@colo.lackof.org> References: <86802c440810091451y4a3caceg1abaa75464c40a72@mail.gmail.com> <20081009225533.GB1914@colo.lackof.org> <48EE8E55.4000009@kernel.org> <20081010114003X.fujita.tomonori@lab.ntt.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081010114003X.fujita.tomonori@lab.ntt.co.jp> X-Home-Page: http://www.parisc-linux.org/ User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1096 Lines: 30 On Fri, Oct 10, 2008 at 11:40:56AM +0900, FUJITA Tomonori wrote: > IIRC, except for one SGI architecture, coherent_dma_mask is > meaningless, dma_mask is always equal to coherent_dma_mask. Not correct. Several PCI-X devices can only do 32-bit DMA to control data but can do 64-bit DMA for payload data. I don't have the list off the top of my head but that is the origin of coherent DMA mask. > Lots of > IOMMU implementations ignore coherent_dma_mask and use dma_mask for > alloc_coherent(). That sounds like a bug. And I don't think it's "lots". > Some drivers don't set up coherent_dma_mask. They probably should. Current default is 32-bits for PCI devices. > Theoretically, we need to fix this but it doesn't cause any > problem. That's why nobody cares about it, I guess. Agreed - for the "supported" configurations, it works. hth, grant -- 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/