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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 B7727C0044D for ; Mon, 16 Mar 2020 09:52:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8C10120658 for ; Mon, 16 Mar 2020 09:52:20 +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="RQY0032q" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730504AbgCPJwT (ORCPT ); Mon, 16 Mar 2020 05:52:19 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:52120 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730088AbgCPJwT (ORCPT ); Mon, 16 Mar 2020 05:52:19 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Transfer-Encoding :Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=9gN1jKXfKNPlMClYtkwzgjKMpTWUcxSWGH8Lo5JSl80=; b=RQY0032qpY4gKVGok/AN5IZj+2 Ed429Gy/OgVbQDSoOHin0HFOSvtFDlSueccW3iBGk30zgEfYdPvXEdbvEtMBwMKjHBcV9xOoF5ZFP hzo1WJbMtDHWzU4LGYKeZVCTcLAhxSMp2nZQLbUPpwwTFiFUtK9GBdnsi3cDVqqTYqdJ6C0AXbn4k qUSLNhAm4dxEbX6LLjkHwS3xhgCrFrRa/4NU9LkzfIRK+CtsZM3MacOUYXr7enCcRiUxgWOrGBYsG kOwvQJ3qOS51mtF1atRsdbzYohMh0Z/cYATwznyk1AT5KgP6tkinFNo8TTilHA16NbVX6plpPsRxU fm7JDlIw==; Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jDmPt-0006MG-C7; Mon, 16 Mar 2020 09:52:13 +0000 Date: Mon, 16 Mar 2020 02:52:13 -0700 From: Christoph Hellwig To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: Christoph Hellwig , Jason Gunthorpe , David1.Zhou@amd.com, daniel@ffwll.ch, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-media@vger.kernel.org, intel-gfx@lists.freedesktop.org, Logan Gunthorpe Subject: Re: [PATCH 1/6] lib/scatterlist: add sg_set_dma_addr() function Message-ID: <20200316095213.GA29212@infradead.org> References: <20200311152838.GA24280@infradead.org> <20200312101943.GA14618@infradead.org> <20200312104729.GA26031@infradead.org> <20200312141928.GK31668@ziepe.ca> <20200313112139.GA4913@infradead.org> <20200313121742.GZ31668@ziepe.ca> <20200316085642.GC1831@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Mon, Mar 16, 2020 at 10:41:42AM +0100, Christian König wrote: > Well I would prefer if the drivers can somehow express their requirements > and get IOVA structures already in the form they need. > > Converting the IOVA data from one form to another is sometimes quite costly. > Especially when it is only temporarily needed. We basically have two ways to generate the IOVA: - a linear translation for the direct mapping case or some dumb IOMMU drivers - in that case case there is a 1:1 mapping between input segments and output segments in DMA mapping - a non-trivial IOMMU where all aligned segments are merged into a single IOVA range So I don't really see how the dma layer could help much with any limitation beyond existing max size and dma boundary ones.