From patchwork Mon Feb 24 18:23:57 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jean-Philippe Brucker X-Patchwork-Id: 204321 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=-9.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 EB9ADC38BF5 for ; Mon, 24 Feb 2020 18:25:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BEFB021556 for ; Mon, 24 Feb 2020 18:25:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="jrea57vR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727891AbgBXSZF (ORCPT ); Mon, 24 Feb 2020 13:25:05 -0500 Received: from mail-wm1-f51.google.com ([209.85.128.51]:34612 "EHLO mail-wm1-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727479AbgBXSY4 (ORCPT ); Mon, 24 Feb 2020 13:24:56 -0500 Received: by mail-wm1-f51.google.com with SMTP id s144so466964wme.1 for ; Mon, 24 Feb 2020 10:24:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=i0VWA2fvKY7B7aVEb87RbBlKKCbdscLm7wXe7hq9l+o=; b=jrea57vRdBhgNK56CGB6FBQaFESTfknRHc96QQ82B0wBh5E8nOIvvqoDp88g21NJms vCtpWf4eZMeIPhoNOEnzXNGWUU/L/DIOMIpzlQ/DLRoBlZsRMavpixederXLjWbnWC7P VgrsbfWlv0djfGH1aSceYJMSD+h2AEC2octSj5r/52HuAkGcmwSLGFyNX2/RJNR0SEXo hjZ4qCxHZra5C4YTiCc/afuFkROLgPCt3wD/HTSI54xo9RGvqdw0v21iw6isZfklwJdL qB7285DeYxybLPJvLl7Ham/dtFKMQ20giHlQ9T+3SZtHeP+2yGyfOLAugLIBycvdgB68 fVnw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=i0VWA2fvKY7B7aVEb87RbBlKKCbdscLm7wXe7hq9l+o=; b=IhNYX1VXJv2YveeRnu1+qx0bL6IVPjFVnUWavQwEVgDaMoI26gHTJCA+rjIBsLI0hO NxJQo8C6LwzNU96WxeAoiIoVaLm4lRa3SDWA6sTHlu+Nee9IbAM++tnstihuvgSS42+X x61SXJFKHYNi27BnXkBkl8043YwHRxu/As4xH+swEiktIlWVONGinqPrAaSM+5whnPNw ag+vF8nB6UtV9gP4ASOKGfzJC4NDmz/D36NbkrInSOuV5EJwrLwX7dRoX5IiDfLv6FOh qg5Nzge9Iw1Z8twzl7Ovdrb8iHDmZEG1ZeNcif9GTfSRNFcPioei48DzLEc0R6oKCrfD PzrQ== X-Gm-Message-State: APjAAAXiVsj3XKPTMvp4W+vzgSkbeRP1HH++ypjKrYN7ecBLCSC18W7K E7LTdz/KiuKC7qAnI5rk+I8dTA== X-Google-Smtp-Source: APXvYqzxdf7GnXuxJz22KdsBgghNsJTC0LtjcF0NB8OgJIKAqhQeqkdamrZEnO7kob3vSOk3XbOcTw== X-Received: by 2002:a7b:c8d2:: with SMTP id f18mr292389wml.47.1582568694023; Mon, 24 Feb 2020 10:24:54 -0800 (PST) Received: from localhost.localdomain ([2001:171b:c9a8:fbc0:116c:c27a:3e7f:5eaf]) by smtp.gmail.com with ESMTPSA id n3sm304255wmc.27.2020.02.24.10.24.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Feb 2020 10:24:53 -0800 (PST) From: Jean-Philippe Brucker To: iommu@lists.linux-foundation.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org, linux-mm@kvack.org Cc: joro@8bytes.org, robh+dt@kernel.org, mark.rutland@arm.com, catalin.marinas@arm.com, will@kernel.org, robin.murphy@arm.com, kevin.tian@intel.com, baolu.lu@linux.intel.com, Jonathan.Cameron@huawei.com, jacob.jun.pan@linux.intel.com, christian.koenig@amd.com, yi.l.liu@intel.com, zhangfei.gao@linaro.org, Jean-Philippe Brucker , Rob Herring Subject: [PATCH v4 22/26] dt-bindings: document stall property for IOMMU masters Date: Mon, 24 Feb 2020 19:23:57 +0100 Message-Id: <20200224182401.353359-23-jean-philippe@linaro.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200224182401.353359-1-jean-philippe@linaro.org> References: <20200224182401.353359-1-jean-philippe@linaro.org> MIME-Version: 1.0 Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org From: Jean-Philippe Brucker On ARM systems, some platform devices behind an IOMMU may support stall, which is the ability to recover from page faults. Let the firmware tell us when a device supports stall. Reviewed-by: Rob Herring Signed-off-by: Jean-Philippe Brucker --- .../devicetree/bindings/iommu/iommu.txt | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/Documentation/devicetree/bindings/iommu/iommu.txt b/Documentation/devicetree/bindings/iommu/iommu.txt index 3c36334e4f94..26ba9e530f13 100644 --- a/Documentation/devicetree/bindings/iommu/iommu.txt +++ b/Documentation/devicetree/bindings/iommu/iommu.txt @@ -92,6 +92,24 @@ Optional properties: tagging DMA transactions with an address space identifier. By default, this is 0, which means that the device only has one address space. +- dma-can-stall: When present, the master can wait for a transaction to + complete for an indefinite amount of time. Upon translation fault some + IOMMUs, instead of aborting the translation immediately, may first + notify the driver and keep the transaction in flight. This allows the OS + to inspect the fault and, for example, make physical pages resident + before updating the mappings and completing the transaction. Such IOMMU + accepts a limited number of simultaneous stalled transactions before + having to either put back-pressure on the master, or abort new faulting + transactions. + + Firmware has to opt-in stalling, because most buses and masters don't + support it. In particular it isn't compatible with PCI, where + transactions have to complete before a time limit. More generally it + won't work in systems and masters that haven't been designed for + stalling. For example the OS, in order to handle a stalled transaction, + may attempt to retrieve pages from secondary storage in a stalled + domain, leading to a deadlock. + Notes: ======