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=-0.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 7C7E3C43387 for ; Tue, 15 Jan 2019 11:31:46 +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 368CF2085A for ; Tue, 15 Jan 2019 11:31:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="sU/EKFpk" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 368CF2085A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au 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:Message-ID:Date:References :In-Reply-To:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=6tMp9vL0UGgYF5qqIkmTD/18GQ83zDcVYuwq6NyySjM=; b=sU/EKFpkViyRRc Ozh3/H8IDvZYobactqdNRhYmaRCEvgWljFLzazYzsWJ8IEJ7lFrygvXHDDOOlBOSLEuxc7ru+JMK9 n0xUR1uzRCP7VUdW9XYZu2fhQIeXR9TO1Zem+4A9N6Fd6Oetu16xP25X7QusocawcxwSuTvMDvoXw XdAzj7EXJCBDnZJhG+k3LWZTR6VZ+5CTIRkc3pmyvM4WvRzkqXuqdAvYEmIBNv+zTF3F1Iqt0qQkh RLN5fNcRwOzt2lLugUzZWo74tYwFLQuBN69ikSSVVfQqzrS+1tbDD1lQT3vbyOsARoUeW70sBtFIX PuTYQ8k5tw3tsINiMC6w==; 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 1gjMwY-00067j-TA; Tue, 15 Jan 2019 11:31:42 +0000 Received: from ozlabs.org ([2401:3900:2:1::2]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1gjMwT-00066n-QI for linux-arm-kernel@lists.infradead.org; Tue, 15 Jan 2019 11:31:40 +0000 Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPSA id 43f7TG5sg3z9sCh; Tue, 15 Jan 2019 22:31:30 +1100 (AEDT) From: Michael Ellerman To: Will Deacon , "Koenig\, Christian" Subject: Re: [RFC PATCH] drm/ttm: force cached mappings for system RAM on ARM In-Reply-To: <20190114193548.GB29600@fuggles.cambridge.arm.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> Date: Tue, 15 Jan 2019 22:31:29 +1100 Message-ID: <87a7k2yx66.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190115_033138_090458_1FA695F3 X-CRM114-Status: UNSURE ( 9.73 ) X-CRM114-Notice: Please train this message. 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 , benh@kernel.crashing.org, Michel =?utf-8?Q?D=C3=A4nz?= =?utf-8?Q?er?= , Linux Kernel Mailing List , dri-devel , "Huang, Ray" , "Zhang, Jerry" , linux-arm-kernel , Bernhard =?utf-8?Q?Rosenkr=C3=A4n?= =?utf-8?Q?zer?= 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 Hi Will, Will Deacon writes: > [+ BenH and MPE] > > On Mon, Jan 14, 2019 at 07:21:08PM +0000, Koenig, Christian wrote: >> Am 14.01.19 um 20:13 schrieb Will Deacon: ... > >> > The Arm architecture (and others including Power afaiu) doesn't >> > guarantee coherency when memory is accessed using mismatched cacheability >> > attributes. ... > >> As far as I know Power doesn't really supports un-cached memory at all, >> except for a very very old and odd configuration with AGP. > > Hopefully Michael/Ben can elaborate here, but I was under the (possibly > mistaken) impression that mismatched attributes could cause a machine-check > on Power. That's what I've always been told, but I can't actually find where it's documented, I'll keep searching. But you're right that mixing cached / uncached is not really supported, and probably results in a machine check or worse. cheers _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel