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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 1B265C4363C for ; Wed, 7 Oct 2020 06:25:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A053B208C7 for ; Wed, 7 Oct 2020 06:25:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="PNf5g862" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726168AbgJGGZ0 (ORCPT ); Wed, 7 Oct 2020 02:25:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41540 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725970AbgJGGZZ (ORCPT ); Wed, 7 Oct 2020 02:25:25 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AEB8CC061755; Tue, 6 Oct 2020 23:25:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=hGY4fKBH3lXrbLnK7loOw4AUvRukRocZITr25lF2ycI=; b=PNf5g8627c2NOMQqhvL0eUPUY9 pG18AoTA0MELpyOL/b9ay/ykTBDatHDGS3jlfCwIic9g3kmcO8E6ny88Ao5zGscnjagnX/WHNFZM5 eZ2NTCUXNprEyCfiCQ/EGzyj6MxRlkn48EyhjY9cX/mqtGmGzUcF/05YoWWqOT3az/7lCzZyLl22/ JnPVX/l/zI1jAPk8897xZBq8Pfmxbi5IX6xg+uZiAsB6ckYTKIB56aoRVnPqszsGMjoVPJQUTNCy1 9FlS3lHhBHqvrySZFyfKyRFMIWGkyvr72addRKiyZPfjxgqJLXANCq04HlVz81s002Ig6I9P5Ekbx glO7NLFQ==; Received: from hch by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kQ2t5-0006Rp-Uy; Wed, 07 Oct 2020 06:25:19 +0000 Date: Wed, 7 Oct 2020 07:25:19 +0100 From: Christoph Hellwig To: Jonathan Marek Cc: Christoph Hellwig , freedreno@lists.freedesktop.org, Rob Clark , Sean Paul , David Airlie , Daniel Vetter , "open list:DRM DRIVER FOR MSM ADRENO GPU" , "open list:DRM DRIVER FOR MSM ADRENO GPU" , open list , iommu@lists.linux-foundation.org, Joerg Roedel , Robin Murphy Subject: Re: [PATCH 2/3] drm/msm: add DRM_MSM_GEM_SYNC_CACHE for non-coherent cache maintenance Message-ID: <20201007062519.GA23519@infradead.org> References: <20201001002709.21361-1-jonathan@marek.ca> <20201001002709.21361-3-jonathan@marek.ca> <20201002075321.GA7547@infradead.org> <20201005082914.GA31702@infradead.org> <3e0b91be-e4a4-4ea5-7d58-6e71b8d51932@marek.ca> <20201006072306.GA12834@infradead.org> <148a1660-f0fc-7163-2240-6b94725342b5@marek.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <148a1660-f0fc-7163-2240-6b94725342b5@marek.ca> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On Tue, Oct 06, 2020 at 09:19:32AM -0400, Jonathan Marek wrote: > One example why drm/msm can't use DMA API is multiple page table support > (that is landing in 5.10), which is something that definitely couldn't work > with DMA API. > > Another one is being able to choose the address for mappings, which AFAIK > DMA API can't do (somewhat related to this: qcom hardware often has ranges > of allowed addresses, which the dma_mask mechanism fails to represent, what > I see is drivers using dma_mask as a "maximum address", and since addresses > are allocated from the top it generally works) That sounds like a good enough rason to use the IOMMU API. I just wanted to make sure this really makes sense.