From patchwork Wed Jan 27 15:43:21 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: 12050489 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=-18.7 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 59CE4C433DB for ; Wed, 27 Jan 2021 15:50:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 08E90207C4 for ; Wed, 27 Jan 2021 15:50:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236004AbhA0Pu1 (ORCPT ); Wed, 27 Jan 2021 10:50:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32822 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236645AbhA0PqX (ORCPT ); Wed, 27 Jan 2021 10:46:23 -0500 Received: from mail-wm1-x334.google.com (mail-wm1-x334.google.com [IPv6:2a00:1450:4864:20::334]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6A567C061353 for ; Wed, 27 Jan 2021 07:44:45 -0800 (PST) Received: by mail-wm1-x334.google.com with SMTP id i9so2081526wmq.1 for ; Wed, 27 Jan 2021 07:44:45 -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=Iza7ai+1pJVkOiREPpK3tUFt/+4KEOcT4kmdIoRu1W4=; b=rbK1aLxadekkDLedlYkhXNNhT2RXl9ArKYIMq5P+xZUhGoeMuNK3hNiCz/AdZv7dFV OSkzpHq8cAXoa/SXmQczZVVsMDUa3zgVBPkpfFJsnMVHytFJ4lPtF7iVgQDdouVwknB6 PKAJ3I0JTJnun9bq1lGNt8cZHMDadB4iIeVL949UJaWXlk8wdS6to9Ss+zGxoSi5GdbL rQVmX44XNm3Yoa6Lp0sLLAnANdFnGsOPlibkhusNtF+Vv0m8ZbNcxG4L4D1R1D/UxyLB XIv8tC7yp0wBkuUigCeJ+XCpBK2QPUanxRD8fKUUvRyaioR65KVTDBWpW69znMpePx9P xlLQ== 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=Iza7ai+1pJVkOiREPpK3tUFt/+4KEOcT4kmdIoRu1W4=; b=IDICIoyTfLqrfz1jEXP4aIin5niP2sbl7rtFuH6ioZV23lpawAkN9Ze2wZzfU1RVrV KjlqtX9n4hfGxm7m5+TbdvvyBw4b2sWex+33vNquGOEr60ouqvdnzA/XH5kfm17eC0eR oCQ/xsuEJ3sbMt3ULHfcCy01LTrCh+iyvhGsVOMA5ir393YAAp/R+7MvsKD0nlsZBk6V Qsh6zExDZyQessrXjkjTPYJFD+EDAPs3JdckE3MgqaFYfKsXj7czVimGMGo7yoq2SrhH gSuTWG1viTm8dFFLh4MgBb+cw4rrIwJpFyMN+WqufEwN6XTHbl+QdWUTegHx1prFXBUK wyrg== X-Gm-Message-State: AOAM533PU7y+tGWUc4FHc2eZDZJwaspDp6QgO7C4YOhK9IZou0n64Zjn MrXqmv0c5ffk/ZXXthCpH1OoLA== X-Google-Smtp-Source: ABdhPJxueLPbEIo5H0DTOaZMTDZgKa24SKwcOb0gi9WAMioQDQ/yigHLDYzBi1GocdkersH1im+GCg== X-Received: by 2002:a1c:2c0b:: with SMTP id s11mr4542706wms.13.1611762284206; Wed, 27 Jan 2021 07:44:44 -0800 (PST) Received: from localhost.localdomain ([2001:1715:4e26:a7e0:116c:c27a:3e7f:5eaf]) by smtp.gmail.com with ESMTPSA id r13sm3046921wmh.9.2021.01.27.07.44.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Jan 2021 07:44:43 -0800 (PST) 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, Jean-Philippe Brucker , Rob Herring Subject: [PATCH v12 08/10] dt-bindings: document stall property for IOMMU masters Date: Wed, 27 Jan 2021 16:43:21 +0100 Message-Id: <20210127154322.3959196-9-jean-philippe@linaro.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210127154322.3959196-1-jean-philippe@linaro.org> References: <20210127154322.3959196-1-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: Rob Herring Signed-off-by: Jean-Philippe Brucker Reviewed-by: Eric Auger --- .../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: ======