From patchwork Thu Jan 21 12:36:22 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: 368065 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 98DA8C433DB for ; Thu, 21 Jan 2021 12:44:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4369B23A01 for ; Thu, 21 Jan 2021 12:44:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728590AbhAUMoC (ORCPT ); Thu, 21 Jan 2021 07:44:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56916 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731142AbhAUMkv (ORCPT ); Thu, 21 Jan 2021 07:40:51 -0500 Received: from mail-wm1-x32c.google.com (mail-wm1-x32c.google.com [IPv6:2a00:1450:4864:20::32c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8B347C06179E for ; Thu, 21 Jan 2021 04:39:42 -0800 (PST) Received: by mail-wm1-x32c.google.com with SMTP id c127so1389409wmf.5 for ; Thu, 21 Jan 2021 04:39:42 -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=ncM2Etu85nnnt1D5R9wUQk3EdfSF9pw+1ijx4nvgrK8oJD23eDuaDfijqTYecFMFyX wDn3pvejZJ45AWRW6k6uYvZj0k+50DwmufnS5BpjT5RFasOCp1okzSAfVbHxJTAkpOjR bFiaj49TLoUmXz50hHl/5dwzxButCVFM8yeIw6pGwP/VnDadugin6h75nubMSCJcAFqO jY17KorelU5Yco4R8uyif+WIeJveoSTMmVpvqNg2IGuEPh6AEA1HXRbFShVjnA2Ncrhu uH+qklVmhowQvcKcP5AUrwxWYPH+BSK1kwjb0JAjJKGJmLV9xrQZONTw0SAGUCP+iOuo n96A== 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=qciSTpIFOBsOjQKbstJEcOIrRPe33ifpP8bxZ9yRV9s1e4zg764XUpJ4ylCRmwGQXi Dihl14gvOb2dNl7k1sR3fIAUhjNYGxoo0doCCzA09+UwdUS8Ndy3Y1lofj6ETh/BjsN6 qjdxTPgTIv3pfwjiyN+Tk6wC8abmQ4ltEAGUHqflG3eq+xkbtU8IpSrLq33h6BImtR5n mDpclcVoOBtI2QR24Lrg4KF765+DH26rT5X2QAwpvElt1hsMBW+Cm+Lox5aRjLwX13Z8 I58AQSAAVC/tjKKP8LTzhFce6HFDAmUy6cqj8FozwM0mrQI+VnQcNqzJ7h726MfBFhnQ lwnw== X-Gm-Message-State: AOAM532U/hg2Rp99BQqcE+XVAcPj/upeDUksfLVM5jWTwK9xCkjTzfL3 bxjpfB87ScOtImTkOpt9f41v+Q== X-Google-Smtp-Source: ABdhPJyyu67AxXul4I8BEhqNEVWy7+2JiEYaRD6cGbSWv/kOI2QhFIZt2cXoy+7w3p9jk6gaghyMpw== X-Received: by 2002:a1c:dc83:: with SMTP id t125mr8923805wmg.154.1611232781283; Thu, 21 Jan 2021 04:39:41 -0800 (PST) Received: from localhost.localdomain ([2001:1715:4e26:a7e0:116c:c27a:3e7f:5eaf]) by smtp.gmail.com with ESMTPSA id p18sm7979248wmc.31.2021.01.21.04.39.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Jan 2021 04:39:40 -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 v10 08/10] dt-bindings: document stall property for IOMMU masters Date: Thu, 21 Jan 2021 13:36:22 +0100 Message-Id: <20210121123623.2060416-9-jean-philippe@linaro.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210121123623.2060416-1-jean-philippe@linaro.org> References: <20210121123623.2060416-1-jean-philippe@linaro.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: devicetree@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 --- .../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: ======