From patchwork Thu Apr 30 14:34:20 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: 11520507 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 92DEC15AB for ; Thu, 30 Apr 2020 14:40:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7B93E217BA for ; Thu, 30 Apr 2020 14:40:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="t+4aT9+c" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728284AbgD3Okp (ORCPT ); Thu, 30 Apr 2020 10:40:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34340 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1728294AbgD3Okp (ORCPT ); Thu, 30 Apr 2020 10:40:45 -0400 Received: from mail-wm1-x341.google.com (mail-wm1-x341.google.com [IPv6:2a00:1450:4864:20::341]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E914C08E934 for ; Thu, 30 Apr 2020 07:40:45 -0700 (PDT) Received: by mail-wm1-x341.google.com with SMTP id v8so7649697wma.0 for ; Thu, 30 Apr 2020 07:40:44 -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=3qbDs4Y7WviMOr0GSY4nlY77EsYqapJLb3Db4qcN97M=; b=t+4aT9+cYprXrpA/0QMDQLTv35ltZRsIzsJhL6WzRIlkGwHMzV+TsilZsqBdYO9os+ LEmbI9poZBOZzYV00yYcZ2MTRGrHanuT7mbSIOQBDmN22wolY/5LERCWxTie3xScd5i+ mfXPYaSrV/1gc4GJ4hkv337jnn0KZarzUW+GAESnsUgwH5AStIsuGwjPrCaZW9BXvAda ze1VdbzDZPXGJXDAcZRAe+Vz+LRVXXtQ68AFPgXXtAqojny8CzAUyLGsI4qjUN9mU9b9 QuzOYgjkRq/kGh890dDfQT+uQE4XjhOzPT2Qd7+Ro83BK/yAfy1ITFBBF/jLhKZ5c5sA 0KPA== 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=3qbDs4Y7WviMOr0GSY4nlY77EsYqapJLb3Db4qcN97M=; b=jJN7NnHTtuLrxlex3dbets5TewZPn2Wflj0wSuWhavXvJtJqmrEQisPFtXWxChoff5 95uHBkjUmDjLInpytgJ18A8G1ia8iKfrZIAAuAp+UXeMJekPd5uX0JvdN4MmCpjbrty1 IGJOU7VqEndiybO8HwL8hPuPyXXtyNiPB11lS2sL8MqWYyYOHdGofCJuIWkoKiYdPhj7 dhnDjSmtfFP7cjVQXyLow8h/e/78gSruBahpC/xpIJ1c8hrDWm3Jz0JkdLJIp/vZsx7E qY4wb/PIvLwpOF0bgDACG/70mJWATPaz0twvhRfVeOET5JN7H8s0vyc+WML8eYf235LF X4Og== X-Gm-Message-State: AGi0PuaTralJnrky/aSqIyLCMcdWFukPIjYbpMkbQ/mMlZFzohCuatUw Jn+kWciDJkmmstXvYXxf7lzGLQ== X-Google-Smtp-Source: APiQypIZMn/sX8HP3LNRMIS2Wr5t5ivHYBY9IZ/xvKKh7rTp8GxPMClKn6Q3u2r37yB03vTCOANl8Q== X-Received: by 2002:a7b:c44d:: with SMTP id l13mr3255113wmi.72.1588257643793; Thu, 30 Apr 2020 07:40:43 -0700 (PDT) Received: from localhost.localdomain ([2001:171b:226e:c200:c43b:ef78:d083:b355]) by smtp.gmail.com with ESMTPSA id n2sm4153286wrt.33.2020.04.30.07.40.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Apr 2020 07:40:43 -0700 (PDT) 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, 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, felix.kuehling@amd.com, zhangfei.gao@linaro.org, jgg@ziepe.ca, xuzaibo@huawei.com, fenghua.yu@intel.com, hch@infradead.org, Jean-Philippe Brucker , Rob Herring Subject: [PATCH v6 21/25] dt-bindings: document stall property for IOMMU masters Date: Thu, 30 Apr 2020 16:34:20 +0200 Message-Id: <20200430143424.2787566-22-jean-philippe@linaro.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200430143424.2787566-1-jean-philippe@linaro.org> References: <20200430143424.2787566-1-jean-philippe@linaro.org> MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@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 3c36334e4f942..26ba9e530f138 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: ======