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Mon, 01 Feb 2021 02:28:19 -0500 X-MC-Unique: _I4TR1CRN0C5u37sUiyijw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 67551801817; Mon, 1 Feb 2021 07:28:16 +0000 (UTC) Received: from [10.36.113.43] (ovpn-113-43.ams2.redhat.com [10.36.113.43]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CA69B70485; Mon, 1 Feb 2021 07:28:09 +0000 (UTC) Subject: Re: [PATCH v12 08/10] dt-bindings: document stall property for IOMMU masters To: Jean-Philippe Brucker , joro@8bytes.org, will@kernel.org References: <20210127154322.3959196-1-jean-philippe@linaro.org> <20210127154322.3959196-9-jean-philippe@linaro.org> From: Auger Eric Message-ID: Date: Mon, 1 Feb 2021 08:28:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20210127154322.3959196-9-jean-philippe@linaro.org> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Cc: devicetree@vger.kernel.org, kevin.tian@intel.com, vivek.gautam@arm.com, guohanjun@huawei.com, rjw@rjwysocki.net, linux-acpi@vger.kernel.org, iommu@lists.linux-foundation.org, robh+dt@kernel.org, linux-accelerators@lists.ozlabs.org, sudeep.holla@arm.com, zhangfei.gao@linaro.org, robin.murphy@arm.com, Rob Herring , linux-arm-kernel@lists.infradead.org, lenb@kernel.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" Hi Jean-Philippe, On 1/27/21 4:43 PM, Jean-Philippe Brucker wrote: > 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 Eric > --- > .../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: > ====== > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu