From patchwork Thu Apr 1 15:47:17 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jean-Philippe Brucker X-Patchwork-Id: 414436 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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, 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 C205AC43616 for ; Thu, 1 Apr 2021 18:31:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9AEA3610C7 for ; Thu, 1 Apr 2021 18:31:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235291AbhDASbx (ORCPT ); Thu, 1 Apr 2021 14:31:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38180 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237025AbhDASWj (ORCPT ); Thu, 1 Apr 2021 14:22:39 -0400 Received: from mail-wr1-x431.google.com (mail-wr1-x431.google.com [IPv6:2a00:1450:4864:20::431]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F0ACCC02D560 for ; Thu, 1 Apr 2021 08:48:22 -0700 (PDT) Received: by mail-wr1-x431.google.com with SMTP id k8so2304122wrc.3 for ; Thu, 01 Apr 2021 08:48:22 -0700 (PDT) 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=qpxpWMnrPJKc07Z7A57L4cT+PGNv1GXXzLI4P6Yd1EE=; b=jFGB9GSoGXYX3K+nuYC/3qk1ccHgek4JlpJBTapcg1kGDi0EdR05JaD/W+kS5Ry4r/ 9jACVmw8RpTQJ6aOuJgcb6f+gsjrqmWJus8aUSvQ+3uHqKAmIezP63nLwJXSJphZ76J4 PwfJzOX9u5yhYHyn3trzzAPq2lI9dQCuJfTjmP+h+DmS1Ij9KW7MP8j+A5EckrmP6ymW YLSf8FR6eUJaHuhk19X4uDd50R2umQSPSWMTVVCqs4CNs5DLQYoQ/VwCDQlAYkUSjA1E OoCkNJREzAOO7+BOlLztBFnSlSDBqlYwLDudahJeNKDwIFxCDvl72kvfg2Q+AXBGz/pP kMGw== 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=qpxpWMnrPJKc07Z7A57L4cT+PGNv1GXXzLI4P6Yd1EE=; b=Jy0sZIxzSLJ8DGII7lUoyVuiIAtAgtKPkLtZmJo+O1ILNiLmzyFjkREEC0u++t6WbK edfEMfJMV0Tno+z+1ZJ3C1SIPXrtFEJhzmA8UAYlWWClhbgBlYbtC/P9K81ZMqb0a77Z zLmX2oeDSdj0pPmmVCMSvIgoSK/RdR5KyvTkPk3lGC3GjJxK6UnRG+EZ9OGqK5gQvAO5 T7WmyLgo8GXDLIS7GoVSbYm/DFF8uFSsgkbS5J7hXjEiyocWjwkfgMf3urn9blq2z5Ht gBU2hcAwDx0ijvKlNtVxJbG04bK6R9zR2IcN1vdNrCTvOnVMhIDmjw0qROYNkSs4qMrg Jrhg== X-Gm-Message-State: AOAM531jsUwh+23lA180/DYbyG0ZkhIoq0lpdv6C7e2IooQtIOgtVeW4 Y/qFYlEafYUwtVs3p+GeDz0ZNg== X-Google-Smtp-Source: ABdhPJz+lVV+B3QqYA925zNmgNgDtjaPx5BumLqk3WkRdxQ7T/gWYzEU6np11tFENpxunZ9tvcBFyg== X-Received: by 2002:adf:fb0e:: with SMTP id c14mr10678009wrr.140.1617292101697; Thu, 01 Apr 2021 08:48:21 -0700 (PDT) Received: from localhost.localdomain ([2001:1715:4e26:a7e0:116c:c27a:3e7f:5eaf]) by smtp.gmail.com with ESMTPSA id y8sm8722505wmi.46.2021.04.01.08.48.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Apr 2021 08:48:21 -0700 (PDT) From: Jean-Philippe Brucker To: joro@8bytes.org, will@kernel.org Cc: lorenzo.pieralisi@arm.com, robh+dt@kernel.org, guohanjun@huawei.com, sudeep.holla@arm.com, rjw@rjwysocki.net, lenb@kernel.org, robin.murphy@arm.com, Jonathan.Cameron@huawei.com, eric.auger@redhat.com, iommu@lists.linux-foundation.org, devicetree@vger.kernel.org, linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-accelerators@lists.ozlabs.org, baolu.lu@linux.intel.com, jacob.jun.pan@linux.intel.com, kevin.tian@intel.com, vdumpa@nvidia.com, zhangfei.gao@linaro.org, shameerali.kolothum.thodi@huawei.com, vivek.gautam@arm.com, zhukeqian1@huawei.com, wangzhou1@hisilicon.com, Jean-Philippe Brucker , Rob Herring Subject: [PATCH v14 08/10] dt-bindings: document stall property for IOMMU masters Date: Thu, 1 Apr 2021 17:47:17 +0200 Message-Id: <20210401154718.307519-9-jean-philippe@linaro.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210401154718.307519-1-jean-philippe@linaro.org> References: <20210401154718.307519-1-jean-philippe@linaro.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org 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: Eric Auger 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: ======