From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932211AbWEAT40 (ORCPT ); Mon, 1 May 2006 15:56:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932214AbWEAT4Z (ORCPT ); Mon, 1 May 2006 15:56:25 -0400 Received: from mail-in-09.arcor-online.net ([151.189.21.49]:55223 "EHLO mail-in-09.arcor-online.net") by vger.kernel.org with ESMTP id S932211AbWEAT4R (ORCPT ); Mon, 1 May 2006 15:56:17 -0400 In-Reply-To: References: <1906950392f7ef8c7d07.1145913778@eng-12.pathscale.com> Mime-Version: 1.0 (Apple Message framework v749.3) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: <4B05D10C-407E-46A5-848F-0897D1E6D1CD@kernel.crashing.org> Cc: "Bryan O'Sullivan" , openib-general@openib.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: 7bit From: Segher Boessenkool Subject: Re: [PATCH 2 of 13] ipath - set up 32-bit DMA mask if 64-bit setup fails Date: Mon, 1 May 2006 21:56:09 +0200 To: Roland Dreier X-Mailer: Apple Mail (2.749.3) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > Bryan> Some systems do not set up 64-bit maps on systems with 2GB > Bryan> or less of memory installed, so we have to fall back to > Bryan> trying a 32-bit setup. > > Which systems does this happen on? PowerPC with U3 or U4 northbridge, i.e. Maple or PowerMac G5 systems. If the IOMMU (DART) is disabled, we have a 32-bit only DMA mask. The DART will be disabled by default if there is 2GB or less of memory (as it isn't needed then). > I'm just curious, because mthca has > > err = pci_set_dma_mask(pdev, DMA_64BIT_MASK); > if (err) { > dev_warn(&pdev->dev, "Warning: couldn't set 64-bit PCI DMA mask. > \n"); > > and I've never had a single report of that warning triggering. That's only because I never used those cards on systems with fewer than 4GB of memory :-) Segher