From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BBEB8C432C0 for ; Thu, 21 Nov 2019 15:26:59 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9759820674 for ; Thu, 21 Nov 2019 15:26:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9759820674 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id 7B0688838E; Thu, 21 Nov 2019 15:26:59 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 4lhQJsw-0xCI; Thu, 21 Nov 2019 15:26:59 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by hemlock.osuosl.org (Postfix) with ESMTP id 065FA88276; Thu, 21 Nov 2019 15:26:59 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id E76F6C1DD8; Thu, 21 Nov 2019 15:26:58 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id CA12BC18DA for ; Thu, 21 Nov 2019 15:26:57 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id B640C88276 for ; Thu, 21 Nov 2019 15:26:57 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id CRzPiJY+Fm8z for ; Thu, 21 Nov 2019 15:26:56 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by hemlock.osuosl.org (Postfix) with ESMTPS id 5B94888188 for ; Thu, 21 Nov 2019 15:26:56 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 9128268BFE; Thu, 21 Nov 2019 16:26:50 +0100 (CET) Date: Thu, 21 Nov 2019 16:26:50 +0100 From: Christoph Hellwig To: Nicolas Saenz Julienne Subject: Re: [PATCH v2] dma-mapping: treat dev->bus_dma_mask as a DMA limit Message-ID: <20191121152650.GA651@lst.de> References: <20191121092646.8449-1-nsaenzjulienne@suse.de> <20191121152457.GA525@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191121152457.GA525@lst.de> User-Agent: Mutt/1.5.17 (2007-11-01) Cc: Peter Zijlstra , Benjamin Herrenschmidt , Dave Hansen , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org, Paul Mackerras , Hanjun Guo , Frank Rowand , Christoph Hellwig , "H. Peter Anvin" , Paul Burton , Michael Ellerman , x86@kernel.org, linux-acpi@vger.kernel.org, Ingo Molnar , James Hogan , Len Brown , devicetree@vger.kernel.org, Rob Herring , Borislav Petkov , Andy Lutomirski , Bjorn Helgaas , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, Jens Axboe , linuxppc-dev@lists.ozlabs.org, "Rafael J. Wysocki" , linux-mips@vger.kernel.org, Ralf Baechle , iommu@lists.linux-foundation.org, Sudeep Holla , Robin Murphy X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Thu, Nov 21, 2019 at 04:24:57PM +0100, Christoph Hellwig wrote: > On Thu, Nov 21, 2019 at 10:26:44AM +0100, Nicolas Saenz Julienne wrote: > > Using a mask to represent bus DMA constraints has a set of limitations. > > The biggest one being it can only hold a power of two (minus one). The > > DMA mapping code is already aware of this and treats dev->bus_dma_mask > > as a limit. This quirk is already used by some architectures although > > still rare. > > > > With the introduction of the Raspberry Pi 4 we've found a new contender > > for the use of bus DMA limits, as its PCIe bus can only address the > > lower 3GB of memory (of a total of 4GB). This is impossible to represent > > with a mask. To make things worse the device-tree code rounds non power > > of two bus DMA limits to the next power of two, which is unacceptable in > > this case. > > > > In the light of this, rename dev->bus_dma_mask to dev->bus_dma_limit all > > over the tree and treat it as such. Note that dev->bus_dma_limit should > > contain the higher accesible DMA address. > > > > Signed-off-by: Nicolas Saenz Julienne > > I've tentatively added this patch to the dma-mapping tree based on > Robins principal approval of the last version. That way tomorrows > linux-next run should still pick it up. Actually. This doesn't apply because the dma-mapping tree doesn't have you zone_dma_bits change. I guess we'll need to wait for the next merge window, or maybe post rc1 if this happens to fix the powerpc problem that Christian reported. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu