From patchwork Wed May 26 16:19:26 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: 12282245 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,USER_AGENT_GIT 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 E36D9C47088 for ; Wed, 26 May 2021 16:21:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C74B461432 for ; Wed, 26 May 2021 16:21:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233901AbhEZQXI (ORCPT ); Wed, 26 May 2021 12:23:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59156 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233822AbhEZQXI (ORCPT ); Wed, 26 May 2021 12:23:08 -0400 Received: from mail-ed1-x529.google.com (mail-ed1-x529.google.com [IPv6:2a00:1450:4864:20::529]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 59D7CC061574 for ; Wed, 26 May 2021 09:21:36 -0700 (PDT) Received: by mail-ed1-x529.google.com with SMTP id w12so2274838edx.1 for ; Wed, 26 May 2021 09:21:36 -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=igtqyM//LYjdds1ytHCniCgg8zwXeW+EZ8GUvM0m2FRDNDeVRq9vskLXhwydDfk8I1 Py+Iv1uCGEMhmYD2qpm+O2OSqMgjpeMutUiLdEcnWGKoeriIt/AE8DKSXYiTUxiyznbe FVzBP6qI4Px6bkTjqE0BruPZj/fjxlr0WhZ7KV8kWd9BbRvRG47PkuIFm0nrg1TTkArn T6b0IDjr4ltS+qRRAtM2FeMsHX0vCGj0W+xGELgKG65hDbF2uQlsZbnB1i5SVT38WK3o 72JWxaT5VTxUZBWIrmWxI2hh1HFSn5kD6YQkLSO9vewdxJhgHUS2S/wf0yd5pzk65gzR 1qZA== 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=KwMbD1a2fmZCpmOTcx0Ti+OoiKCNn5TlhGNd82DfdLNI10gUk6AVmAHknobNO0X7rQ 5j/sUIkqqP+p7hYFDyq0LcpqEefZhinoP9/m3K0B8qRBt5dZgpqyUdeYt7TP6lm8/A7h hbMzQoCJufSUJ1yCIAYlV3YeuLKloy+cUuWFPjfA7yEI/13dtToBeikjETp3vdy59ew9 YhBveAbLvXVSXLynrRb5Q58GWcE1gEHMwZJ1Tqmt0RRGtSK7PXRwVOmvO7Ou3aM+IBvn AqBCwqEZ8JHtgQ7Z/ruuojJ/E5NJZouoih5GyRrEBsPurV9QlNV9zFt47rEpX6jGkD24 lc1w== X-Gm-Message-State: AOAM53257xidpNPfXmbnIMT0AADKYAXepkzjVsw7i8tDTsLn70mqaJhg 2LXUswNjbEnaV8fGnabmqryUdA== X-Google-Smtp-Source: ABdhPJzV0Ekj4Q8KGq3C6oAPDF07bqX/LfHaYKNeHot9cZ4TZoZePl+V6GNvhy0kwuByEYqcvxu6qg== X-Received: by 2002:aa7:c152:: with SMTP id r18mr38149878edp.266.1622046094940; Wed, 26 May 2021 09:21:34 -0700 (PDT) Received: from localhost.localdomain (adsl-84-226-106-126.adslplus.ch. [84.226.106.126]) by smtp.gmail.com with ESMTPSA id e6sm10497145ejd.31.2021.05.26.09.21.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 May 2021 09:21:34 -0700 (PDT) From: Jean-Philippe Brucker To: joro@8bytes.org, will@kernel.org Cc: robh+dt@kernel.org, lorenzo.pieralisi@arm.com, 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, zhangfei.gao@linaro.org, wangzhou1@hisilicon.com, iommu@lists.linux-foundation.org, devicetree@vger.kernel.org, linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Jean-Philippe Brucker , Rob Herring Subject: [PATCH v15 1/3] dt-bindings: document stall property for IOMMU masters Date: Wed, 26 May 2021 18:19:26 +0200 Message-Id: <20210526161927.24268-2-jean-philippe@linaro.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210526161927.24268-1-jean-philippe@linaro.org> References: <20210526161927.24268-1-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: ======