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=-2.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED 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 71363C43387 for ; Thu, 17 Jan 2019 06:00:40 +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 3A01320854 for ; Thu, 17 Jan 2019 06:00:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="pq+ejmuG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3A01320854 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org 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:Mime-Version:References:In-Reply-To: Date:To:From:Subject:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=rh5CXnbaZPoNgZDsR6uKvpa5+kE7l2m1OO2uCZQPwHs=; b=pq+ejmuGN6Ef1V kxwTC4siSH374thb7wt4cgQI8kirltE9HWkbw2I7KlJd2+EyFKDBtw7ClF7+VEAATtQCJKu3r5rK4 XdTbxItKluDk9/oow/JVsFWC4soxurD7LKd7saAIjrPob8pgEP7bztMiv1WZrVOfvtXLn+HgxjjBS g96bxmXV8sewiThwOnMhTJdvMbLf5ImP1jYS9LqhmV38JsU4kZpPbi5RzMUUkmzPrMKmK/5rjQeIE H00sxmwi/+Fn+ycWbITdVKaVeuuk2hfOqHFqj27Fd7Rm/rZJeOXJtAyv9g/UPh8TVbRFypcSjasHH l6FXuxcTbQilySxgsSsA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gk0jG-0006C9-Rp; Thu, 17 Jan 2019 06:00:38 +0000 Received: from gate.crashing.org ([63.228.1.57]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1gk0jD-0006Bd-To for linux-arm-kernel@lists.infradead.org; Thu, 17 Jan 2019 06:00:37 +0000 Received: from localhost (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id x0H5xrlO023594; Wed, 16 Jan 2019 23:59:54 -0600 Message-ID: Subject: Re: [RFC PATCH] drm/ttm: force cached mappings for system RAM on ARM From: Benjamin Herrenschmidt To: "Koenig, Christian" , Michael Ellerman , Will Deacon Date: Thu, 17 Jan 2019 16:59:53 +1100 In-Reply-To: <9dc27cbf-e109-0c32-fc92-6fce1b224cda@amd.com> References: <20190110072841.3283-1-ard.biesheuvel@linaro.org> <5d8135de-80fe-9c0e-2206-ecb809f64cdb@daenzer.net> <55facfb9-92af-86b8-40e9-d63b887b5592@amd.com> <9f956898-7973-98ee-6bf1-e1d445e9d365@amd.com> <20190114191350.GA29600@fuggles.cambridge.arm.com> <20190114193548.GB29600@fuggles.cambridge.arm.com> <87a7k2yx66.fsf@concordia.ellerman.id.au> <9dc27cbf-e109-0c32-fc92-6fce1b224cda@amd.com> User-Agent: Evolution 3.30.4 (3.30.4-1.fc29) Mime-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190116_220036_179698_71505B35 X-CRM114-Status: GOOD ( 13.04 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Carsten Haitzler , Ard Biesheuvel , David Airlie , Michel =?ISO-8859-1?Q?D=E4nzer?= , Linux Kernel Mailing List , dri-devel , "Huang, Ray" , "Zhang, Jerry" , linux-arm-kernel , Bernhard =?ISO-8859-1?Q?Rosenkr=E4nzer?= 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 Wed, 2019-01-16 at 07:35 +0000, Koenig, Christian wrote: > No, but you answer the wrong question. > > See we don't want to have different mappings of cached and non-cached on > the CPU, but rather want to know if a snooped DMA from the PCIe counts > as cached access as well. > > As far as I know on x86 it doesn't, so when you have an un-cached page > you can still access it with a snooping DMA read/write operation and > don't cause trouble. Hrm... well, if you map it uncached on the CPU on powerpc, a snoop DMA will work fine too, it won't hit any cache. The only problem I'm aware of is a core (or CAPI device) emiting non-cached load/stores colliding with a cache snooper. > > The old hack of using non-cached mapping to avoid snoop cost in AGP and > > others is just that ... an ugly and horrible hacks that should have > > never eventuated, when the search for performance pushes HW people into > > utter insanity :) > > Well I agree that un-cached system memory makes things much more > complicated for a questionable gain. > > But fact is we now have to deal with the mess, so no point in > complaining about it to much :) I wish we could just sent the HW designers home and tell them we won't support that crap... oh well. Ben. > Cheers, > Christian. > > > Cheers, > > Ben. > > > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel