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=-5.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 54BF3C4727E for ; Mon, 21 Sep 2020 22:24:43 +0000 (UTC) Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (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 DE3CE23A62 for ; Mon, 21 Sep 2020 22:24:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="x1+tx4t5" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DE3CE23A62 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id BBE3920522; Mon, 21 Sep 2020 22:24:42 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id UqLOJI6nf34s; Mon, 21 Sep 2020 22:24:42 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by silver.osuosl.org (Postfix) with ESMTP id 1285120015; Mon, 21 Sep 2020 22:24:42 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 0B28DC0859; Mon, 21 Sep 2020 22:24:42 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 4A24EC0051 for ; Mon, 21 Sep 2020 22:24:41 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id 2D6D88506F for ; Mon, 21 Sep 2020 22:24:41 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ImV7sh3biOux for ; Mon, 21 Sep 2020 22:24:40 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by whitealder.osuosl.org (Postfix) with ESMTPS id 5D76984FBB for ; Mon, 21 Sep 2020 22:24:40 +0000 (UTC) Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2157523A63; Mon, 21 Sep 2020 22:24:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600727080; bh=1PUJ5hNzZTNJHRrWsG3qH9Ptt+duX4WCMYgHNreOFF4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=x1+tx4t5xnc8rNe7UWv5d0zvDRXkj6XToXs0Pyf/+5XHpb3DF5wqgSaHpgyzmVx3V 7ZoJ+jLyb8mOgdPTOYNlXScX9cHDSUghI946B+JsMOUk0PvUp1YpH3s62uCof9b8Jf XGpyPrxLFD8nYYIX4fWIYYzjfp/D1vv/F9ThLdAA= Date: Mon, 21 Sep 2020 23:24:34 +0100 From: Will Deacon To: Robin Murphy Subject: Re: [PATCH 1/3] iommu/io-pgtable-arm: Support coherency for Mali LPAE Message-ID: <20200921222434.GB4409@willie-the-truck> References: <20200921175717.GF3141@willie-the-truck> <71cc6c53-7bd1-da1a-05fa-8172510b33d8@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <71cc6c53-7bd1-da1a-05fa-8172510b33d8@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Cc: robh@kernel.org, tomeu.vizoso@collabora.com, narmstrong@baylibre.com, khilman@baylibre.com, dri-devel@lists.freedesktop.org, steven.price@arm.com, iommu@lists.linux-foundation.org, alyssa.rosenzweig@collabora.com, linux-amlogic@lists.infradead.org, linux-arm-kernel@lists.infradead.org, jbrunet@baylibre.com X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Mon, Sep 21, 2020 at 10:53:23PM +0100, Robin Murphy wrote: > On 2020-09-21 18:57, Will Deacon wrote: > > On Wed, Sep 16, 2020 at 12:51:05AM +0100, Robin Murphy wrote: > > > Midgard GPUs have ACE-Lite master interfaces which allows systems to > > > integrate them in an I/O-coherent manner. It seems that from the GPU's > > > viewpoint, the rest of the system is its outer shareable domain, and so > > > even when snoop signals are wired up, they are only emitted for outer > > > shareable accesses. As such, setting the TTBR_SHARE_OUTER bit does > > > indeed get coherent pagetable walks working nicely for the coherent > > > T620 in the Arm Juno SoC. > > > > I can't help but think some of this commentary deserves to be in the code > > as well. > > Sure, if you want. Yes, please. > > Do you know if this sort of thing is done for other SoCs too, or is this > > just a Juno quirk? > > Yup, this is a "Midgard working as designed" thing. Juno is the coherent > example I have to hand, but off the top of my head I believe some of the > Exynos SoCs can also use their GPUs coherently if a switch is flipped in the > interconnect to change routing between the CCI and a direct-to-RAM path; I > expect there are probably further Midgard examples that I'm not aware of. > Then there are definitely coherent Bifrost GPUs like the Amlogic S922/A311 > that prompted me to revive this patch, which we currently drive in "Legacy" > mode and thus behave the same way as Midgard (Bifrost's "AArch64" mode > realigns Ish and Osh with the rest of the system, and instead invents a new > "Internal Shareable" value in between Nsh and Ish to represent the > shareability between cores within the GPU for which Midgard hijacked Ish). That is more than I wanted to know :) "Internal Shareable", jeez... Thanks, Will _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu 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=-7.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 89916C4727C for ; Mon, 21 Sep 2020 22:26:03 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 34AE023A63 for ; Mon, 21 Sep 2020 22:26:03 +0000 (UTC) Authentication-Results: mail.kernel.org; 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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600727080; bh=1PUJ5hNzZTNJHRrWsG3qH9Ptt+duX4WCMYgHNreOFF4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=x1+tx4t5xnc8rNe7UWv5d0zvDRXkj6XToXs0Pyf/+5XHpb3DF5wqgSaHpgyzmVx3V 7ZoJ+jLyb8mOgdPTOYNlXScX9cHDSUghI946B+JsMOUk0PvUp1YpH3s62uCof9b8Jf XGpyPrxLFD8nYYIX4fWIYYzjfp/D1vv/F9ThLdAA= Date: Mon, 21 Sep 2020 23:24:34 +0100 From: Will Deacon To: Robin Murphy Subject: Re: [PATCH 1/3] iommu/io-pgtable-arm: Support coherency for Mali LPAE Message-ID: <20200921222434.GB4409@willie-the-truck> References: <20200921175717.GF3141@willie-the-truck> <71cc6c53-7bd1-da1a-05fa-8172510b33d8@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <71cc6c53-7bd1-da1a-05fa-8172510b33d8@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200921_182440_860801_AC0B42CF X-CRM114-Status: GOOD ( 23.36 ) 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: robh@kernel.org, tomeu.vizoso@collabora.com, narmstrong@baylibre.com, khilman@baylibre.com, dri-devel@lists.freedesktop.org, steven.price@arm.com, iommu@lists.linux-foundation.org, alyssa.rosenzweig@collabora.com, linux-amlogic@lists.infradead.org, linux-arm-kernel@lists.infradead.org, jbrunet@baylibre.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Sep 21, 2020 at 10:53:23PM +0100, Robin Murphy wrote: > On 2020-09-21 18:57, Will Deacon wrote: > > On Wed, Sep 16, 2020 at 12:51:05AM +0100, Robin Murphy wrote: > > > Midgard GPUs have ACE-Lite master interfaces which allows systems to > > > integrate them in an I/O-coherent manner. It seems that from the GPU's > > > viewpoint, the rest of the system is its outer shareable domain, and so > > > even when snoop signals are wired up, they are only emitted for outer > > > shareable accesses. As such, setting the TTBR_SHARE_OUTER bit does > > > indeed get coherent pagetable walks working nicely for the coherent > > > T620 in the Arm Juno SoC. > > > > I can't help but think some of this commentary deserves to be in the code > > as well. > > Sure, if you want. Yes, please. > > Do you know if this sort of thing is done for other SoCs too, or is this > > just a Juno quirk? > > Yup, this is a "Midgard working as designed" thing. Juno is the coherent > example I have to hand, but off the top of my head I believe some of the > Exynos SoCs can also use their GPUs coherently if a switch is flipped in the > interconnect to change routing between the CCI and a direct-to-RAM path; I > expect there are probably further Midgard examples that I'm not aware of. > Then there are definitely coherent Bifrost GPUs like the Amlogic S922/A311 > that prompted me to revive this patch, which we currently drive in "Legacy" > mode and thus behave the same way as Midgard (Bifrost's "AArch64" mode > realigns Ish and Osh with the rest of the system, and instead invents a new > "Internal Shareable" value in between Nsh and Ish to represent the > shareability between cores within the GPU for which Midgard hijacked Ish). That is more than I wanted to know :) "Internal Shareable", jeez... Thanks, Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel 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=-5.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 3CAD9C4727C for ; Mon, 21 Sep 2020 22:24:42 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (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 E008923A65 for ; Mon, 21 Sep 2020 22:24:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="x1+tx4t5" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E008923A65 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 2AC8889D9A; Mon, 21 Sep 2020 22:24:41 +0000 (UTC) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by gabe.freedesktop.org (Postfix) with ESMTPS id 34CA989D9A for ; Mon, 21 Sep 2020 22:24:40 +0000 (UTC) Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2157523A63; Mon, 21 Sep 2020 22:24:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600727080; bh=1PUJ5hNzZTNJHRrWsG3qH9Ptt+duX4WCMYgHNreOFF4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=x1+tx4t5xnc8rNe7UWv5d0zvDRXkj6XToXs0Pyf/+5XHpb3DF5wqgSaHpgyzmVx3V 7ZoJ+jLyb8mOgdPTOYNlXScX9cHDSUghI946B+JsMOUk0PvUp1YpH3s62uCof9b8Jf XGpyPrxLFD8nYYIX4fWIYYzjfp/D1vv/F9ThLdAA= Date: Mon, 21 Sep 2020 23:24:34 +0100 From: Will Deacon To: Robin Murphy Subject: Re: [PATCH 1/3] iommu/io-pgtable-arm: Support coherency for Mali LPAE Message-ID: <20200921222434.GB4409@willie-the-truck> References: <20200921175717.GF3141@willie-the-truck> <71cc6c53-7bd1-da1a-05fa-8172510b33d8@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <71cc6c53-7bd1-da1a-05fa-8172510b33d8@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: tomeu.vizoso@collabora.com, narmstrong@baylibre.com, khilman@baylibre.com, dri-devel@lists.freedesktop.org, steven.price@arm.com, iommu@lists.linux-foundation.org, alyssa.rosenzweig@collabora.com, linux-amlogic@lists.infradead.org, linux-arm-kernel@lists.infradead.org, jbrunet@baylibre.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Mon, Sep 21, 2020 at 10:53:23PM +0100, Robin Murphy wrote: > On 2020-09-21 18:57, Will Deacon wrote: > > On Wed, Sep 16, 2020 at 12:51:05AM +0100, Robin Murphy wrote: > > > Midgard GPUs have ACE-Lite master interfaces which allows systems to > > > integrate them in an I/O-coherent manner. It seems that from the GPU's > > > viewpoint, the rest of the system is its outer shareable domain, and so > > > even when snoop signals are wired up, they are only emitted for outer > > > shareable accesses. As such, setting the TTBR_SHARE_OUTER bit does > > > indeed get coherent pagetable walks working nicely for the coherent > > > T620 in the Arm Juno SoC. > > > > I can't help but think some of this commentary deserves to be in the code > > as well. > > Sure, if you want. Yes, please. > > Do you know if this sort of thing is done for other SoCs too, or is this > > just a Juno quirk? > > Yup, this is a "Midgard working as designed" thing. Juno is the coherent > example I have to hand, but off the top of my head I believe some of the > Exynos SoCs can also use their GPUs coherently if a switch is flipped in the > interconnect to change routing between the CCI and a direct-to-RAM path; I > expect there are probably further Midgard examples that I'm not aware of. > Then there are definitely coherent Bifrost GPUs like the Amlogic S922/A311 > that prompted me to revive this patch, which we currently drive in "Legacy" > mode and thus behave the same way as Midgard (Bifrost's "AArch64" mode > realigns Ish and Osh with the rest of the system, and instead invents a new > "Internal Shareable" value in between Nsh and Ish to represent the > shareability between cores within the GPU for which Midgard hijacked Ish). That is more than I wanted to know :) "Internal Shareable", jeez... Thanks, Will _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel 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=-7.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 1F8FBC4727C for ; Mon, 21 Sep 2020 22:24:50 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 B690223A63 for ; Mon, 21 Sep 2020 22:24:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="dYwnAIe7"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="x1+tx4t5" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B690223A63 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.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=BAkYi62k+l0EugOXczIGUx6HNX9Q7KFMZhibhLIQYks=; b=dYwnAIe7nqgLWo6s31b8GVwct QX7H+vMm9nWayWdtE6qQjeIAiuYwlaVahG9D/fqKHse7BQ/tNXU2ioI9IBpczmHoIW78qK1JUOHuh Y/CNCGfDyfs2Q13Al/Gv/XZPFmjEqpExBUnLF6ynh/Z4MA90PLYfiiL1E8STwGaVrMG+N9Uigiphl juloW9g2I/ebkCIJ845kZyaQ8FyFVXLcPKPtrDK/+XvF1mDX5f7+RrjG+ULBo027KYskZuJ5dmfYo puIMXqEGHFUkgIoFtoTmLvs8Wpw4JjRFEFHh5pUqsuJ38XIPmL5bDrrJ4OjFoOiTHLxTxkQoav0Eb 6XVddtUFQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kKUEl-0000ng-0P; Mon, 21 Sep 2020 22:24:43 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kKUEi-0000mV-Oj; Mon, 21 Sep 2020 22:24:41 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2157523A63; Mon, 21 Sep 2020 22:24:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600727080; bh=1PUJ5hNzZTNJHRrWsG3qH9Ptt+duX4WCMYgHNreOFF4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=x1+tx4t5xnc8rNe7UWv5d0zvDRXkj6XToXs0Pyf/+5XHpb3DF5wqgSaHpgyzmVx3V 7ZoJ+jLyb8mOgdPTOYNlXScX9cHDSUghI946B+JsMOUk0PvUp1YpH3s62uCof9b8Jf XGpyPrxLFD8nYYIX4fWIYYzjfp/D1vv/F9ThLdAA= Date: Mon, 21 Sep 2020 23:24:34 +0100 From: Will Deacon To: Robin Murphy Subject: Re: [PATCH 1/3] iommu/io-pgtable-arm: Support coherency for Mali LPAE Message-ID: <20200921222434.GB4409@willie-the-truck> References: <20200921175717.GF3141@willie-the-truck> <71cc6c53-7bd1-da1a-05fa-8172510b33d8@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <71cc6c53-7bd1-da1a-05fa-8172510b33d8@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200921_182440_860801_AC0B42CF X-CRM114-Status: GOOD ( 23.36 ) X-BeenThere: linux-amlogic@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: robh@kernel.org, tomeu.vizoso@collabora.com, narmstrong@baylibre.com, khilman@baylibre.com, dri-devel@lists.freedesktop.org, steven.price@arm.com, iommu@lists.linux-foundation.org, alyssa.rosenzweig@collabora.com, linux-amlogic@lists.infradead.org, linux-arm-kernel@lists.infradead.org, jbrunet@baylibre.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-amlogic" Errors-To: linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org On Mon, Sep 21, 2020 at 10:53:23PM +0100, Robin Murphy wrote: > On 2020-09-21 18:57, Will Deacon wrote: > > On Wed, Sep 16, 2020 at 12:51:05AM +0100, Robin Murphy wrote: > > > Midgard GPUs have ACE-Lite master interfaces which allows systems to > > > integrate them in an I/O-coherent manner. It seems that from the GPU's > > > viewpoint, the rest of the system is its outer shareable domain, and so > > > even when snoop signals are wired up, they are only emitted for outer > > > shareable accesses. As such, setting the TTBR_SHARE_OUTER bit does > > > indeed get coherent pagetable walks working nicely for the coherent > > > T620 in the Arm Juno SoC. > > > > I can't help but think some of this commentary deserves to be in the code > > as well. > > Sure, if you want. Yes, please. > > Do you know if this sort of thing is done for other SoCs too, or is this > > just a Juno quirk? > > Yup, this is a "Midgard working as designed" thing. Juno is the coherent > example I have to hand, but off the top of my head I believe some of the > Exynos SoCs can also use their GPUs coherently if a switch is flipped in the > interconnect to change routing between the CCI and a direct-to-RAM path; I > expect there are probably further Midgard examples that I'm not aware of. > Then there are definitely coherent Bifrost GPUs like the Amlogic S922/A311 > that prompted me to revive this patch, which we currently drive in "Legacy" > mode and thus behave the same way as Midgard (Bifrost's "AArch64" mode > realigns Ish and Osh with the rest of the system, and instead invents a new > "Internal Shareable" value in between Nsh and Ish to represent the > shareability between cores within the GPU for which Midgard hijacked Ish). That is more than I wanted to know :) "Internal Shareable", jeez... Thanks, Will _______________________________________________ linux-amlogic mailing list linux-amlogic@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-amlogic