Re: [PATCH v2 1/5] dt-bindings: virtio: Specify #iommu-cells value for a virtio-iommu

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Tue, Jun 26, 2018 at 11:59 AM Jean-Philippe Brucker
<jean-philippe.brucker@xxxxxxx> wrote:
>
> On 25/06/18 20:27, Rob Herring wrote:
> > On Thu, Jun 21, 2018 at 08:06:51PM +0100, Jean-Philippe Brucker wrote:
> >> A virtio-mmio node may represent a virtio-iommu device. This is discovered
> >> by the virtio driver at probe time, but the DMA topology isn't
> >> discoverable and must be described by firmware. For DT the standard IOMMU
> >> description is used, as specified in bindings/iommu/iommu.txt and
> >> bindings/pci/pci-iommu.txt. Like many other IOMMUs, virtio-iommu
> >> distinguishes masters by their endpoint IDs, which requires one IOMMU cell
> >> in the "iommus" property.
> >>
> >> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>
> >> ---
> >>  Documentation/devicetree/bindings/virtio/mmio.txt | 8 ++++++++
> >>  1 file changed, 8 insertions(+)
> >>
> >> diff --git a/Documentation/devicetree/bindings/virtio/mmio.txt b/Documentation/devicetree/bindings/virtio/mmio.txt
> >> index 5069c1b8e193..337da0e3a87f 100644
> >> --- a/Documentation/devicetree/bindings/virtio/mmio.txt
> >> +++ b/Documentation/devicetree/bindings/virtio/mmio.txt
> >> @@ -8,6 +8,14 @@ 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 describes a virtio-iommu device, it is
> >> +            linked to DMA masters using the "iommus" property as
> >> +            described in devicetree/bindings/iommu/iommu.txt. For
> >> +            virtio-iommu #iommu-cells must be 1, each cell describing
> >> +            a single endpoint ID.
> >
> > The iommus property should also be documented for the client side.
>
> Isn't section "IOMMU master node" of iommu.txt sufficient? Since the
> iommus property applies to any DMA master, not only virtio-mmio devices,
> the canonical description in iommu.txt seems the best place for it, and
> I'm not sure what to add in this file. Maybe a short example below the
> virtio_block one?

No, because somewhere we have to capture if 'iommus' is valid for
'virtio-mmio' or not. Hopefully soon we'll actually be able to
validate that.

Rob
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Device Tree Compilter]     [Device Tree Spec]     [Linux Driver Backports]     [Video for Linux]     [Linux USB Devel]     [Linux PCI Devel]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Yosemite Backpacking]


  Powered by Linux