Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932630Ab0HDMEH (ORCPT ); Wed, 4 Aug 2010 08:04:07 -0400 Received: from sh.osrg.net ([192.16.179.4]:45858 "EHLO sh.osrg.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932478Ab0HDMEE (ORCPT ); Wed, 4 Aug 2010 08:04:04 -0400 Date: Wed, 4 Aug 2010 21:03:53 +0900 To: sa212+lkml@cyconix.com Cc: linux-kernel@vger.kernel.org, fujita.tomonori@lab.ntt.co.jp, x86@kernel.org Subject: Re: Driver: PCIe: 'pci_map_sg' returning invalid bus address? From: FUJITA Tomonori In-Reply-To: <4C594D78.6090407@cyconix.com> References: <4C593245.5070303@cyconix.com> <20100804190808D.fujita.tomonori@lab.ntt.co.jp> <4C594D78.6090407@cyconix.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: <20100804210206A.fujita.tomonori@lab.ntt.co.jp> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-3.0 (sh.osrg.net [192.16.179.4]); Wed, 04 Aug 2010 21:03:54 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1848 Lines: 39 On Wed, 04 Aug 2010 12:22:32 +0100 Evan Lavelle wrote: > FUJITA Tomonori wrote: > >> Made some progress here. The problem is that this is 32-bit PAE kernel, > >> so 'dma_addr_t' is 64-bit. However, I have a 32-bit PCIe card, so I need > >> a 32-bit dma_addr_t. How do I do this? In other words, how do I handle > >> 32-bit PCI cards on PAE or 64-bit systems? My code sets the DMA mask to > >> 32 bits but this is *not* sufficient: > >> > >> pci_set_dma_mask(my_dev, DMA_32BIT_MASK) > > > > It doesn't work on x86_32 kernel if your driver doesn't work with the > > block layer or the network subsystem. > > Sorry, not sure that I understand this. Are you saying that I can't set > a DMA mask on x86_32 unless I have a block or network driver? Yeah, the mask is ignored. As I wrote in the previous mail, x86_32 doesn't have a bounce mechanism so dma_map_{single|sg} can't do anything for a buffer above 32bit even if the mask is 32bit. > > If your driver can't handle 64bit DMA, you need bounce buffer. > > The problem is not that I can't handle 64-bit DMA in the driver, but > that the PCI card can't do 64-bit DMA. I tell the kernel this by calling > 'pci_set_dma_mask' with a 32-bit mask, but it appears to be ignoring my > request and then giving me a 64-bit dma_addr_t for the 32-bit PCI card. If your card can't do 64-bit DMA, you need a bounce buffer mechanism. Options are: - your driver implements its own bounce buffer mechanism (as some driver do). - add swiotlb support to x86_32 (I don't think that it's difficult but I might miss something). -- 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/