From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030829AbWKUKaQ (ORCPT ); Tue, 21 Nov 2006 05:30:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030831AbWKUKaQ (ORCPT ); Tue, 21 Nov 2006 05:30:16 -0500 Received: from cantor2.suse.de ([195.135.220.15]:24965 "EHLO mx2.suse.de") by vger.kernel.org with ESMTP id S1030829AbWKUKaP (ORCPT ); Tue, 21 Nov 2006 05:30:15 -0500 To: Larry Finger Cc: Ray Lee , linux-kernel@vger.kernel.org Subject: Re: Problem with DMA on x86_64 with 3 GB RAM References: <455B63EC.8070704@madrabbit.org> <20061118112438.GB15349@nineveh.rivenstone.net> <1163868955.27188.2.camel@johannes.berg> <455F3D44.4010502@lwfinger.net> <455F4271.1060405@madrabbit.org> <455FF672.4070502@lwfinger.net> From: Andi Kleen Date: 21 Nov 2006 11:30:00 +0100 In-Reply-To: <455FF672.4070502@lwfinger.net> Message-ID: User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Larry Finger writes: > I am trying to debug a bcm43xx DMA problem on an x86_64 system with 3 > GB RAM. Depending on the particular chip and its implementation, dma > transfers may use 64-, 32-, or 30-bit addressing, with the problem > interface using 30-bit addressing. From test prints, the correct mask > (0x3FFFFFFF) is supplied to pci_set_dma_mask and > pci_set_consistent_dma_mask. Neither call returns an error. In > addition, several x86_64 systems with more than 1 GB RAM have worked > with the current code. 30bit DMA has be bounced through GFP_DMA. The driver needs special code for this. You can look at the b44 driver for a working reference. The pci_dma_* interfaces on x86-64 only support masks >= 0xffffffff, anything smaller has to be handled manually. -Andi