From mboxrd@z Thu Jan 1 00:00:00 1970 From: Auger Eric Subject: Re: [PATCH v3 1/7] dt-bindings: virtio-mmio: Add IOMMU description Date: Thu, 15 Nov 2018 09:45:32 +0100 Message-ID: <02c507c1-6f64-5116-756a-e0a23b32fe2a@redhat.com> References: <20181012145917.6840-1-jean-philippe.brucker@arm.com> <20181012145917.6840-2-jean-philippe.brucker@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20181012145917.6840-2-jean-philippe.brucker@arm.com> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Jean-Philippe Brucker , iommu@lists.linux-foundation.org, virtualization@lists.linux-foundation.org, devicetree@vger.kernel.org Cc: mark.rutland@arm.com, peter.maydell@linaro.org, lorenzo.pieralisi@arm.com, tnowicki@caviumnetworks.com, mst@redhat.com, marc.zyngier@arm.com, linux-pci@vger.kernel.org, will.deacon@arm.com, kvmarm@lists.cs.columbia.edu, robh+dt@kernel.org, robin.murphy@arm.com, joro@8bytes.org List-Id: devicetree@vger.kernel.org Hi Jean, On 10/12/18 4:59 PM, Jean-Philippe Brucker wrote: > The nature of a virtio-mmio node is discovered by the virtio driver at > probe time. However the DMA relation between devices must be described > statically. When a virtio-mmio node is a virtio-iommu device, it needs an > "#iommu-cells" property as specified by bindings/iommu/iommu.txt. > > Otherwise, the virtio-mmio device may perform DMA through an IOMMU, which > requires an "iommus" property. Describe these requirements in the > device-tree bindings documentation. > > Signed-off-by: Jean-Philippe Brucker > --- > .../devicetree/bindings/virtio/mmio.txt | 30 +++++++++++++++++++ > 1 file changed, 30 insertions(+) > > diff --git a/Documentation/devicetree/bindings/virtio/mmio.txt b/Documentation/devicetree/bindings/virtio/mmio.txt > index 5069c1b8e193..748595473b36 100644 > --- a/Documentation/devicetree/bindings/virtio/mmio.txt > +++ b/Documentation/devicetree/bindings/virtio/mmio.txt > @@ -8,10 +8,40 @@ Required properties: > - reg: control registers base address and size including configuration space > - interrupts: interrupt generated by the device > > +Required properties for virtio-iommu: > + > +- #iommu-cells: When the node corresponds to a virtio-iommu device, it is > + linked to DMA masters using the "iommus" or "iommu-map" > + properties [1][2]. #iommu-cells specifies the size of the > + "iommus" property. For virtio-iommu #iommu-cells must be > + 1, each cell describing a single endpoint ID. > + > +Optional properties: > + > +- iommus: If the device accesses memory through an IOMMU, it should > + have an "iommus" property [1]. Since virtio-iommu itself > + does not access memory through an IOMMU, the "virtio,mmio" > + node cannot have both an "#iommu-cells" and an "iommus" > + property. > + > Example: > > virtio_block@3000 { > compatible = "virtio,mmio"; > reg = <0x3000 0x100>; > interrupts = <41>; > + > + /* Device has endpoint ID 23 */ > + iommus = <&viommu 23> > } > + > + viommu: virtio_iommu@3100 { > + compatible = "virtio,mmio"; > + reg = <0x3100 0x100>; > + interrupts = <42>; > + > + #iommu-cells = <1> > + } > + > +[1] Documentation/devicetree/bindings/iommu/iommu.txt > +[2] Documentation/devicetree/bindings/pci/pci-iommu.txt > Reviewed-by: Eric Auger Thanks Eric