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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 47876C47258 for ; Wed, 17 Jan 2024 22:24:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:Message-ID:In-Reply-To: Subject:cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=WzW1Fk5u32O+yb2K52S2yBaCbke0eV3AI5kNOXrG8fc=; b=qc4d/ikq4jkducwXazRzn3WNL3 DUQ94R2ziZM6EOZ/tkXLKzK2uhq9FVE4YXANmhAfHA2T6BAM8mU58J6zx1P7QQWby5hFukuQM1OTl Plu9RDPAGwELHzTTJ/sudGYtBU8bIar9lJ7wkQJvXkOUSYBKgdsH1Je3m+W38+NKNXfyc/2tl0v1z G2d7BOtElvINi6XxOaQcblrzvmOhT+RcWunr7vrdlOZd8LQsRrXavuWqujeYJrzPwzl4a4jHECEfV /NW2Sdxc1h0QB61P30EoRRr0Lnp1RksxC7mYiPaNmOvtaQsWqWsSiyAtvUVq+/FueV8CcnRuKUHJE ok2ZvusA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1rQEJt-000vjy-2h; Wed, 17 Jan 2024 22:23:37 +0000 Received: from gentwo.org ([62.72.0.81]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1rQEJq-000vjT-36 for linux-arm-kernel@lists.infradead.org; Wed, 17 Jan 2024 22:23:36 +0000 Received: by gentwo.org (Postfix, from userid 1003) id 614C940A8B; Wed, 17 Jan 2024 14:23:33 -0800 (PST) Received: from localhost (localhost [127.0.0.1]) by gentwo.org (Postfix) with ESMTP id 5A16540A85; Wed, 17 Jan 2024 14:23:33 -0800 (PST) Date: Wed, 17 Jan 2024 14:23:33 -0800 (PST) From: "Christoph Lameter (Ampere)" To: Baruch Siach cc: Christoph Hellwig , Marek Szyprowski , Rob Herring , Frank Rowand , Catalin Marinas , Will Deacon , Robin Murphy , iommu@lists.linux.dev, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, =?ISO-8859-2?Q?Petr_Tesa=F8=EDk?= , Ramon Fried Subject: Re: [PATCH RFC 1/4] of: get dma area lower limit In-Reply-To: Message-ID: <30d81f73-e27e-6cc4-5458-686e3ddd2e5c@linux.com> References: MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240117_142335_018361_B5FB5FF0 X-CRM114-Status: UNSURE ( 9.37 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, 27 Dec 2023, Baruch Siach wrote: > of_dma_get_max_cpu_address() returns the highest CPU address that > devices can use for DMA. The implicit assumption is that all CPU > addresses below that limit are suitable for DMA. However the > 'dma-ranges' property this code uses also encodes a lower limit for DMA > that is potentially non zero. All of memory can be used for DMA by default (==ZONE_NORMAL). ZONE_DMA defines a special range for devices that are unable to perform DMA to all of memory. Usually due to the lack of address bit support. So I guess that the platform in question here has as a general limit as to what address spaces I/O devices can do DMA to? _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel