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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 E3296C3A59B for ; Mon, 19 Aug 2019 05:23:50 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id B5CA82087E for ; Mon, 19 Aug 2019 05:23:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="YRbcA2xK" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B5CA82087E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject: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=TQd5l4yQO/LSB2dI7T1twLqtgx+j9VfVWTtu9SAqWu8=; b=YRbcA2xKM2C5JJ rLfU08zX+Od/3Nu6KlC/18Nmwh2s07ZojCJY7ZutyzF/H5hCNImutTI5PopksAAClg5qa2r3vOmBN aS4UgQQtbZUF0D9wjYPVioq0fm6eAH4Rsf88wnYyQO0dWDqv8PsT2IodQAf59v3aGdTDUnc8m7mGd IScMCHi/YsQtqFh5tbSNUFt3KwWdaSu/SXtLTG3sKm4k34VP1bsqFYQMwA9bgQwihoLuReqoAqKoL WIL2dxVFkkvMauK/KILEOTI6pk8QeyHjTc2uyjwIyU0TjDTtZ0PxO9nXZcbFjUV9TwGXkHtoAIuMY R/ac01Musqf6A5HVWJbg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hza90-00052M-5W; Mon, 19 Aug 2019 05:23:50 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1hza8x-00051w-4X for linux-arm-kernel@lists.infradead.org; Mon, 19 Aug 2019 05:23:48 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 736F768B02; Mon, 19 Aug 2019 07:23:37 +0200 (CEST) Date: Mon, 19 Aug 2019 07:23:37 +0200 From: Christoph Hellwig To: Rob Clark Subject: Re: [PATCH 0/6] drm+dma: cache support for arm, etc Message-ID: <20190819052337.GA16622@lst.de> References: <20190814220011.26934-1-robdclark@gmail.com> <20190815065117.GA23761@lst.de> <20190815175346.GA19839@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190818_222347_331192_B40C4C4B X-CRM114-Status: GOOD ( 14.76 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kate Stewart , Masayoshi Mizuma , "Maciej W. Rozycki" , Eric Biggers , Catalin Marinas , Imre Deak , dri-devel , Chris Wilson , Masahiro Yamada , Benjamin Gaignard , Mauro Carvalho Chehab , Will Deacon , Christoph Hellwig , Emil Velikov , Deepak Sharma , Michael Ellerman , Paul Burton , Mike Rapoport , Geert Uytterhoeven , "moderated list:ARM64 PORT \(AARCH64 ARCHITECTURE\)" , Daniel Vetter , "open list:MIPS" , Linus Walleij , Robin Murphy , "open list:DRM DRIVER FOR MSM ADRENO GPU" , Joerg Roedel , Arnd Bergmann , Anshuman Khandual , Hauke Mehrtens , Jesper Dangaard Brouer , "Wolfram Sang \(Renesas\)" , "open list:LINUX FOR POWERPC \(32-BIT AND 64-BIT\)" , Alexios Zavras , Russell King , Doug Anderson , Thomas Gleixner , Sean Paul , Allison Randal , Christophe Leroy , Enrico Weigelt , Ard Biesheuvel , Greg Kroah-Hartman , open list , Rob Clark , Souptick Joarder , Andrew Morton , "open list:DRM DRIVER FOR MSM ADRENO GPU" , christian.koenig@amd.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Aug 16, 2019 at 02:04:35PM -0700, Rob Clark wrote: > I don't disagree about needing an API to get uncached memory (or > ideally just something outside of the linear map). But I think this > is a separate problem. > > What I was hoping for, for v5.4, is a way to stop abusing dma_map/sync > for cache ops to get rid of the hack I had to make for v5.3. And also > to fix vgem on non-x86. (Unfortunately changing vgem to used cached > mappings breaks x86 CI, but fixes CI on arm/arm64..) We can do that > without any changes in allocation. There is still the possibility for > problems due to cached alias, but that has been a problem this whole > time, it isn't something new. But that just means we start exposing random low-level APIs that people will quickly abuse.. In fact even your simple plan to some extent already is an abuse of the intent of these functions, and it also requires a lot of knowledge in the driver that in the normal cases drivers can't know (e.g. is the device dma coherent or not). _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel