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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 B432BC282C2 for ; Thu, 7 Feb 2019 07:16:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7CFE12147C for ; Thu, 7 Feb 2019 07:16:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="YDtR7P4Z" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726700AbfBGHQh (ORCPT ); Thu, 7 Feb 2019 02:16:37 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:39020 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725923AbfBGHQg (ORCPT ); Thu, 7 Feb 2019 02:16:36 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=so5q6TjpGxAOvmkdcR8//fWOl4z6ZFvizvjphmN4+MA=; b=YDtR7P4ZgLpd2Rl1fCGqmnCC2 Buoo+xJlfs3myD3RQXQY2TAn84mxR09oa/IMZIB+G/vOJtTmVH5NHkErrgl+tsMBfaYYrU3OUFw7m orYvF1aHiaQ0H4VXW/EVeiELfN2wUMK0wps3+7LzSVKl/ujFG34RhViaGG2OytbJVU5ViYfc0vAIr U97kTVb70VMPMwMO4UyR3Pa6ja+4AL2fvsD8ANhd7DFGRI+iDWh3FqubXDIXJlOYLP6Ml/h+xlwMd j7h/kffrThOQcRPT/izHxzTTN9ep3J07lKj0uO7XRsV//8RSP3hlK8/R1TTYg5iZKkN9FbEihO+7C VnoGFydDw==; Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1grdvF-0001Cz-Eu; Thu, 07 Feb 2019 07:16:33 +0000 Date: Wed, 6 Feb 2019 23:16:33 -0800 From: Christoph Hellwig To: Dmitry Osipenko Cc: Thierry Reding , Sowjanya Komatineni , jonathanh@nvidia.com, mkarthik@nvidia.com, smohammed@nvidia.com, talho@nvidia.com, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org Subject: Re: [PATCH V11 3/5] i2c: tegra: Add DMA support Message-ID: <20190207071633.GA25149@infradead.org> References: <1549356985-25726-1-git-send-email-skomatineni@nvidia.com> <1549356985-25726-3-git-send-email-skomatineni@nvidia.com> <20190206145343.GA3651@ulmo> <5e66803c-b13b-cb00-e2ff-d096a1650612@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5e66803c-b13b-cb00-e2ff-d096a1650612@gmail.com> User-Agent: Mutt/1.9.2 (2017-12-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 06, 2019 at 05:56:02PM +0300, Dmitry Osipenko wrote: > > We don't have an IOMMU attached to I2C or APBDMA, so this can't happen > > and even if we had an IOMMU attached, all we care about is the device's > > DMA address space, which means IOVA space, and that would still be > > guaranteed to be contiguous, according to the above. > > Yes, but doesn't T186+ have IOMMU support for the DMA controller? Even if it did, why would that matter? The device would only see IOVA space, the CPU for a normal driver only sees kernel virtual space. Forced contiguous space only makes sense when you have access by CPU physical address, which should not happen for "normal" device drivers.