diff mbox series

[v2] dt-bindings: iommu: Convert Arm SMMUv3 to DT schema

Message ID 20191014191256.12697-1-robh@kernel.org
State Accepted
Commit b5c8c6ded32e6dbad29422c0c83bebfac8810d61
Headers show
Series [v2] dt-bindings: iommu: Convert Arm SMMUv3 to DT schema | expand

Commit Message

Rob Herring Oct. 14, 2019, 7:12 p.m. UTC
Convert the Arm SMMv3 binding to the DT schema format.

Cc: Joerg Roedel <joro@8bytes.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Robin Murphy <Robin.Murphy@arm.com>
Cc: iommu@lists.linux-foundation.org
Signed-off-by: Rob Herring <robh@kernel.org>

---
v2:
- Refine interrupt definition based on Robin's comments

 .../devicetree/bindings/iommu/arm,smmu-v3.txt |  77 --------------
 .../bindings/iommu/arm,smmu-v3.yaml           | 100 ++++++++++++++++++
 2 files changed, 100 insertions(+), 77 deletions(-)
 delete mode 100644 Documentation/devicetree/bindings/iommu/arm,smmu-v3.txt
 create mode 100644 Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml

-- 
2.20.1

Comments

Robin Murphy Oct. 22, 2019, 4:54 p.m. UTC | #1
On 14/10/2019 20:12, Rob Herring wrote:
> Convert the Arm SMMv3 binding to the DT schema format.

> 

> Cc: Joerg Roedel <joro@8bytes.org>

> Cc: Mark Rutland <mark.rutland@arm.com>

> Cc: Will Deacon <will@kernel.org>

> Cc: Robin Murphy <Robin.Murphy@arm.com>

> Cc: iommu@lists.linux-foundation.org

> Signed-off-by: Rob Herring <robh@kernel.org>

> ---

> v2:

> - Refine interrupt definition based on Robin's comments

> 

>   .../devicetree/bindings/iommu/arm,smmu-v3.txt |  77 --------------

>   .../bindings/iommu/arm,smmu-v3.yaml           | 100 ++++++++++++++++++

>   2 files changed, 100 insertions(+), 77 deletions(-)

>   delete mode 100644 Documentation/devicetree/bindings/iommu/arm,smmu-v3.txt

>   create mode 100644 Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml

> 

> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.txt b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.txt

> deleted file mode 100644

> index c9abbf3e4f68..000000000000

> --- a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.txt

> +++ /dev/null

> @@ -1,77 +0,0 @@

> -* ARM SMMUv3 Architecture Implementation

> -

> -The SMMUv3 architecture is a significant departure from previous

> -revisions, replacing the MMIO register interface with in-memory command

> -and event queues and adding support for the ATS and PRI components of

> -the PCIe specification.

> -

> -** SMMUv3 required properties:

> -

> -- compatible        : Should include:

> -

> -                      * "arm,smmu-v3" for any SMMUv3 compliant

> -                        implementation. This entry should be last in the

> -                        compatible list.

> -

> -- reg               : Base address and size of the SMMU.

> -

> -- interrupts        : Non-secure interrupt list describing the wired

> -                      interrupt sources corresponding to entries in

> -                      interrupt-names. If no wired interrupts are

> -                      present then this property may be omitted.

> -

> -- interrupt-names   : When the interrupts property is present, should

> -                      include the following:

> -                      * "eventq"    - Event Queue not empty

> -                      * "priq"      - PRI Queue not empty

> -                      * "cmdq-sync" - CMD_SYNC complete

> -                      * "gerror"    - Global Error activated

> -                      * "combined"  - The combined interrupt is optional,

> -				      and should only be provided if the

> -				      hardware supports just a single,

> -				      combined interrupt line.

> -				      If provided, then the combined interrupt

> -				      will be used in preference to any others.

> -

> -- #iommu-cells      : See the generic IOMMU binding described in

> -                        devicetree/bindings/pci/pci-iommu.txt

> -                      for details. For SMMUv3, must be 1, with each cell

> -                      describing a single stream ID. All possible stream

> -                      IDs which a device may emit must be described.

> -

> -** SMMUv3 optional properties:

> -

> -- dma-coherent      : Present if DMA operations made by the SMMU (page

> -                      table walks, stream table accesses etc) are cache

> -                      coherent with the CPU.

> -

> -                      NOTE: this only applies to the SMMU itself, not

> -                      masters connected upstream of the SMMU.

> -

> -- msi-parent        : See the generic MSI binding described in

> -                        devicetree/bindings/interrupt-controller/msi.txt

> -                      for a description of the msi-parent property.

> -

> -- hisilicon,broken-prefetch-cmd

> -                    : Avoid sending CMD_PREFETCH_* commands to the SMMU.

> -

> -- cavium,cn9900-broken-page1-regspace

> -                    : Replaces all page 1 offsets used for EVTQ_PROD/CONS,

> -		      PRIQ_PROD/CONS register access with page 0 offsets.

> -		      Set for Cavium ThunderX2 silicon that doesn't support

> -		      SMMU page1 register space.

> -

> -** Example

> -

> -        smmu@2b400000 {

> -                compatible = "arm,smmu-v3";

> -                reg = <0x0 0x2b400000 0x0 0x20000>;

> -                interrupts = <GIC_SPI 74 IRQ_TYPE_EDGE_RISING>,

> -                             <GIC_SPI 75 IRQ_TYPE_EDGE_RISING>,

> -                             <GIC_SPI 77 IRQ_TYPE_EDGE_RISING>,

> -                             <GIC_SPI 79 IRQ_TYPE_EDGE_RISING>;

> -                interrupt-names = "eventq", "priq", "cmdq-sync", "gerror";

> -                dma-coherent;

> -                #iommu-cells = <1>;

> -                msi-parent = <&its 0xff0000>;

> -        };

> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml

> new file mode 100644

> index 000000000000..662cbc4592c9

> --- /dev/null

> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml

> @@ -0,0 +1,100 @@

> +# SPDX-License-Identifier: GPL-2.0-only

> +%YAML 1.2

> +---

> +$id: http://devicetree.org/schemas/iommu/arm,smmu-v3.yaml#

> +$schema: http://devicetree.org/meta-schemas/core.yaml#

> +

> +title: ARM SMMUv3 Architecture Implementation

> +

> +maintainers:

> +  - Will Deacon <will@kernel.org>

> +  - Robin Murphy <Robin.Murphy@arm.com>

> +

> +description: |+

> +  The SMMUv3 architecture is a significant departure from previous

> +  revisions, replacing the MMIO register interface with in-memory command

> +  and event queues and adding support for the ATS and PRI components of

> +  the PCIe specification.

> +

> +properties:

> +  $nodename:

> +    pattern: "^iommu@[0-9a-f]*"

> +  compatible:

> +    const: arm,smmu-v3

> +

> +  reg:

> +    maxItems: 1

> +

> +  interrupts:

> +    minItems: 1

> +    maxItems: 4

> +

> +  interrupt-names:

> +    oneOf:

> +      - const: combined

> +        description:

> +          The combined interrupt is optional, and should only be provided if the

> +          hardware supports just a single, combined interrupt line.

> +          If provided, then the combined interrupt will be used in preference to

> +          any others.

> +      - items:

> +          - const: eventq     # Event Queue not empt

> +          - const: priq       # PRI Queue not empty

> +          - const: cmdq-sync  # CMD_SYNC complete

> +          - const: gerror     # Global Error activated


Isn't this effectively redundant with the 4-item case of the version 
below? If it's purely about the ordering, and we can't express "one or 
more of any of:" without spelling out all 64 possible permutations, then 
TBH I'd rather just settle on a single definition that can work for all 
current cases and update the Fast Model DT if necessary.

Otherwise, though, this looks like a fair starting point to me;

Reviewed-by: Robin Murphy <robin.murphy@arm.com>


> +      - minItems: 2

> +        maxItems: 4

> +        items:

> +          - const: eventq

> +          - const: gerror

> +          - const: priq

> +          - const: cmdq-sync

> +

> +  '#iommu-cells':

> +    const: 1

> +

> +  dma-coherent:

> +    description: |

> +      Present if page table walks made by the SMMU are cache coherent with the

> +      CPU.

> +

> +      NOTE: this only applies to the SMMU itself, not masters connected

> +      upstream of the SMMU.

> +

> +  msi-parent: true

> +

> +  hisilicon,broken-prefetch-cmd:

> +    type: boolean

> +    description: Avoid sending CMD_PREFETCH_* commands to the SMMU.

> +

> +  cavium,cn9900-broken-page1-regspace:

> +    type: boolean

> +    description:

> +      Replaces all page 1 offsets used for EVTQ_PROD/CONS, PRIQ_PROD/CONS

> +      register access with page 0 offsets. Set for Cavium ThunderX2 silicon that

> +      doesn't support SMMU page1 register space.

> +

> +required:

> +  - compatible

> +  - reg

> +  - '#iommu-cells'

> +

> +additionalProperties: false

> +

> +examples:

> +  - |+

> +    #include <dt-bindings/interrupt-controller/arm-gic.h>

> +    #include <dt-bindings/interrupt-controller/irq.h>

> +

> +    iommu@2b400000 {

> +            compatible = "arm,smmu-v3";

> +            reg = <0x2b400000 0x20000>;

> +            interrupts = <GIC_SPI 74 IRQ_TYPE_EDGE_RISING>,

> +                         <GIC_SPI 75 IRQ_TYPE_EDGE_RISING>,

> +                         <GIC_SPI 77 IRQ_TYPE_EDGE_RISING>,

> +                         <GIC_SPI 79 IRQ_TYPE_EDGE_RISING>;

> +            interrupt-names = "eventq", "priq", "cmdq-sync", "gerror";

> +            dma-coherent;

> +            #iommu-cells = <1>;

> +            msi-parent = <&its 0xff0000>;

> +    };

>
Will Deacon Nov. 1, 2019, 5:08 p.m. UTC | #2
Hi Rob,

On Mon, Oct 14, 2019 at 02:12:56PM -0500, Rob Herring wrote:
> Convert the Arm SMMv3 binding to the DT schema format.

> 

> Cc: Joerg Roedel <joro@8bytes.org>

> Cc: Mark Rutland <mark.rutland@arm.com>

> Cc: Will Deacon <will@kernel.org>

> Cc: Robin Murphy <Robin.Murphy@arm.com>

> Cc: iommu@lists.linux-foundation.org

> Signed-off-by: Rob Herring <robh@kernel.org>

> ---

> v2:

> - Refine interrupt definition based on Robin's comments

> 

>  .../devicetree/bindings/iommu/arm,smmu-v3.txt |  77 --------------

>  .../bindings/iommu/arm,smmu-v3.yaml           | 100 ++++++++++++++++++

>  2 files changed, 100 insertions(+), 77 deletions(-)

>  delete mode 100644 Documentation/devicetree/bindings/iommu/arm,smmu-v3.txt

>  create mode 100644 Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml


[...]

> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml

> new file mode 100644

> index 000000000000..662cbc4592c9

> --- /dev/null

> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml

> @@ -0,0 +1,100 @@

> +# SPDX-License-Identifier: GPL-2.0-only

> +%YAML 1.2

> +---

> +$id: http://devicetree.org/schemas/iommu/arm,smmu-v3.yaml#

> +$schema: http://devicetree.org/meta-schemas/core.yaml#

> +

> +title: ARM SMMUv3 Architecture Implementation

> +

> +maintainers:

> +  - Will Deacon <will@kernel.org>

> +  - Robin Murphy <Robin.Murphy@arm.com>

> +

> +description: |+

> +  The SMMUv3 architecture is a significant departure from previous

> +  revisions, replacing the MMIO register interface with in-memory command

> +  and event queues and adding support for the ATS and PRI components of

> +  the PCIe specification.

> +

> +properties:

> +  $nodename:

> +    pattern: "^iommu@[0-9a-f]*"

> +  compatible:

> +    const: arm,smmu-v3

> +

> +  reg:

> +    maxItems: 1

> +

> +  interrupts:

> +    minItems: 1

> +    maxItems: 4

> +

> +  interrupt-names:

> +    oneOf:

> +      - const: combined

> +        description:

> +          The combined interrupt is optional, and should only be provided if the

> +          hardware supports just a single, combined interrupt line.

> +          If provided, then the combined interrupt will be used in preference to

> +          any others.

> +      - items:

> +          - const: eventq     # Event Queue not empt

> +          - const: priq       # PRI Queue not empty

> +          - const: cmdq-sync  # CMD_SYNC complete

> +          - const: gerror     # Global Error activated

> +      - minItems: 2

> +        maxItems: 4

> +        items:

> +          - const: eventq

> +          - const: gerror

> +          - const: priq

> +          - const: cmdq-sync


I find it a bit odd to say "minItems: 2" here since, for example, if you
have an SMMU that supports PRI then you really want the PRIQ interrupt
hooked up. The only one never care about in the current driver is cmdq-sync,
but that's just a driver quirk.

Also, if the thing supports MSIs then it might not have any wired interrupts
at all. Hmm.

> +

> +  '#iommu-cells':

> +    const: 1

> +

> +  dma-coherent:

> +    description: |

> +      Present if page table walks made by the SMMU are cache coherent with the

> +      CPU.


This looks like you've taken the text from SMMUv2 by accident. For SMMUv3,
it's not just about page table walks, but *any* DMA operations made by the
SMMU (e.g. STE lookup). I don't see the need to change the current text tbh.

Will
Rob Herring Nov. 1, 2019, 8:14 p.m. UTC | #3
On Fri, Nov 1, 2019 at 12:08 PM Will Deacon <will@kernel.org> wrote:
>

> Hi Rob,

>

> On Mon, Oct 14, 2019 at 02:12:56PM -0500, Rob Herring wrote:

> > Convert the Arm SMMv3 binding to the DT schema format.

> >

> > Cc: Joerg Roedel <joro@8bytes.org>

> > Cc: Mark Rutland <mark.rutland@arm.com>

> > Cc: Will Deacon <will@kernel.org>

> > Cc: Robin Murphy <Robin.Murphy@arm.com>

> > Cc: iommu@lists.linux-foundation.org

> > Signed-off-by: Rob Herring <robh@kernel.org>

> > ---

> > v2:

> > - Refine interrupt definition based on Robin's comments

> >

> >  .../devicetree/bindings/iommu/arm,smmu-v3.txt |  77 --------------

> >  .../bindings/iommu/arm,smmu-v3.yaml           | 100 ++++++++++++++++++

> >  2 files changed, 100 insertions(+), 77 deletions(-)

> >  delete mode 100644 Documentation/devicetree/bindings/iommu/arm,smmu-v3.txt

> >  create mode 100644 Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml

>

> [...]

>

> > diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml

> > new file mode 100644

> > index 000000000000..662cbc4592c9

> > --- /dev/null

> > +++ b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml

> > @@ -0,0 +1,100 @@

> > +# SPDX-License-Identifier: GPL-2.0-only

> > +%YAML 1.2

> > +---

> > +$id: http://devicetree.org/schemas/iommu/arm,smmu-v3.yaml#

> > +$schema: http://devicetree.org/meta-schemas/core.yaml#

> > +

> > +title: ARM SMMUv3 Architecture Implementation

> > +

> > +maintainers:

> > +  - Will Deacon <will@kernel.org>

> > +  - Robin Murphy <Robin.Murphy@arm.com>

> > +

> > +description: |+

> > +  The SMMUv3 architecture is a significant departure from previous

> > +  revisions, replacing the MMIO register interface with in-memory command

> > +  and event queues and adding support for the ATS and PRI components of

> > +  the PCIe specification.

> > +

> > +properties:

> > +  $nodename:

> > +    pattern: "^iommu@[0-9a-f]*"

> > +  compatible:

> > +    const: arm,smmu-v3

> > +

> > +  reg:

> > +    maxItems: 1

> > +

> > +  interrupts:

> > +    minItems: 1

> > +    maxItems: 4

> > +

> > +  interrupt-names:

> > +    oneOf:

> > +      - const: combined

> > +        description:

> > +          The combined interrupt is optional, and should only be provided if the

> > +          hardware supports just a single, combined interrupt line.

> > +          If provided, then the combined interrupt will be used in preference to

> > +          any others.

> > +      - items:

> > +          - const: eventq     # Event Queue not empt

> > +          - const: priq       # PRI Queue not empty

> > +          - const: cmdq-sync  # CMD_SYNC complete

> > +          - const: gerror     # Global Error activated

> > +      - minItems: 2

> > +        maxItems: 4

> > +        items:

> > +          - const: eventq

> > +          - const: gerror

> > +          - const: priq

> > +          - const: cmdq-sync

>

> I find it a bit odd to say "minItems: 2" here since, for example, if you

> have an SMMU that supports PRI then you really want the PRIQ interrupt

> hooked up. The only one never care about in the current driver is cmdq-sync,

> but that's just a driver quirk.


I don't know. I'm just documenting what exists and doesn't seem like
an outright error. The one case is TI:

arch/arm64/boot/dts/ti/k3-j721e-main.dtsi:
interrupt-names = "eventq", "gerror";

If we want to make priq conditionally required, then I need to know
which compatibles would imply supporting PRI. If that's discoverable,
then we can't really enforce the interrupt being present in the
schema.

> Also, if the thing supports MSIs then it might not have any wired interrupts

> at all. Hmm.


That would be why 'interrupts' is optional. The schema only applies if
a property is present.

> > +  '#iommu-cells':

> > +    const: 1

> > +

> > +  dma-coherent:

> > +    description: |

> > +      Present if page table walks made by the SMMU are cache coherent with the

> > +      CPU.

>

> This looks like you've taken the text from SMMUv2 by accident. For SMMUv3,

> it's not just about page table walks, but *any* DMA operations made by the

> SMMU (e.g. STE lookup). I don't see the need to change the current text tbh.


Indeed. I'll do a follow-up as I've already applied these 2 patches.

Rob
diff mbox series

Patch

diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.txt b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.txt
deleted file mode 100644
index c9abbf3e4f68..000000000000
--- a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.txt
+++ /dev/null
@@ -1,77 +0,0 @@ 
-* ARM SMMUv3 Architecture Implementation
-
-The SMMUv3 architecture is a significant departure from previous
-revisions, replacing the MMIO register interface with in-memory command
-and event queues and adding support for the ATS and PRI components of
-the PCIe specification.
-
-** SMMUv3 required properties:
-
-- compatible        : Should include:
-
-                      * "arm,smmu-v3" for any SMMUv3 compliant
-                        implementation. This entry should be last in the
-                        compatible list.
-
-- reg               : Base address and size of the SMMU.
-
-- interrupts        : Non-secure interrupt list describing the wired
-                      interrupt sources corresponding to entries in
-                      interrupt-names. If no wired interrupts are
-                      present then this property may be omitted.
-
-- interrupt-names   : When the interrupts property is present, should
-                      include the following:
-                      * "eventq"    - Event Queue not empty
-                      * "priq"      - PRI Queue not empty
-                      * "cmdq-sync" - CMD_SYNC complete
-                      * "gerror"    - Global Error activated
-                      * "combined"  - The combined interrupt is optional,
-				      and should only be provided if the
-				      hardware supports just a single,
-				      combined interrupt line.
-				      If provided, then the combined interrupt
-				      will be used in preference to any others.
-
-- #iommu-cells      : See the generic IOMMU binding described in
-                        devicetree/bindings/pci/pci-iommu.txt
-                      for details. For SMMUv3, must be 1, with each cell
-                      describing a single stream ID. All possible stream
-                      IDs which a device may emit must be described.
-
-** SMMUv3 optional properties:
-
-- dma-coherent      : Present if DMA operations made by the SMMU (page
-                      table walks, stream table accesses etc) are cache
-                      coherent with the CPU.
-
-                      NOTE: this only applies to the SMMU itself, not
-                      masters connected upstream of the SMMU.
-
-- msi-parent        : See the generic MSI binding described in
-                        devicetree/bindings/interrupt-controller/msi.txt
-                      for a description of the msi-parent property.
-
-- hisilicon,broken-prefetch-cmd
-                    : Avoid sending CMD_PREFETCH_* commands to the SMMU.
-
-- cavium,cn9900-broken-page1-regspace
-                    : Replaces all page 1 offsets used for EVTQ_PROD/CONS,
-		      PRIQ_PROD/CONS register access with page 0 offsets.
-		      Set for Cavium ThunderX2 silicon that doesn't support
-		      SMMU page1 register space.
-
-** Example
-
-        smmu@2b400000 {
-                compatible = "arm,smmu-v3";
-                reg = <0x0 0x2b400000 0x0 0x20000>;
-                interrupts = <GIC_SPI 74 IRQ_TYPE_EDGE_RISING>,
-                             <GIC_SPI 75 IRQ_TYPE_EDGE_RISING>,
-                             <GIC_SPI 77 IRQ_TYPE_EDGE_RISING>,
-                             <GIC_SPI 79 IRQ_TYPE_EDGE_RISING>;
-                interrupt-names = "eventq", "priq", "cmdq-sync", "gerror";
-                dma-coherent;
-                #iommu-cells = <1>;
-                msi-parent = <&its 0xff0000>;
-        };
diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml
new file mode 100644
index 000000000000..662cbc4592c9
--- /dev/null
+++ b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml
@@ -0,0 +1,100 @@ 
+# SPDX-License-Identifier: GPL-2.0-only
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iommu/arm,smmu-v3.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ARM SMMUv3 Architecture Implementation
+
+maintainers:
+  - Will Deacon <will@kernel.org>
+  - Robin Murphy <Robin.Murphy@arm.com>
+
+description: |+
+  The SMMUv3 architecture is a significant departure from previous
+  revisions, replacing the MMIO register interface with in-memory command
+  and event queues and adding support for the ATS and PRI components of
+  the PCIe specification.
+
+properties:
+  $nodename:
+    pattern: "^iommu@[0-9a-f]*"
+  compatible:
+    const: arm,smmu-v3
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    minItems: 1
+    maxItems: 4
+
+  interrupt-names:
+    oneOf:
+      - const: combined
+        description:
+          The combined interrupt is optional, and should only be provided if the
+          hardware supports just a single, combined interrupt line.
+          If provided, then the combined interrupt will be used in preference to
+          any others.
+      - items:
+          - const: eventq     # Event Queue not empt
+          - const: priq       # PRI Queue not empty
+          - const: cmdq-sync  # CMD_SYNC complete
+          - const: gerror     # Global Error activated
+      - minItems: 2
+        maxItems: 4
+        items:
+          - const: eventq
+          - const: gerror
+          - const: priq
+          - const: cmdq-sync
+
+  '#iommu-cells':
+    const: 1
+
+  dma-coherent:
+    description: |
+      Present if page table walks made by the SMMU are cache coherent with the
+      CPU.
+
+      NOTE: this only applies to the SMMU itself, not masters connected
+      upstream of the SMMU.
+
+  msi-parent: true
+
+  hisilicon,broken-prefetch-cmd:
+    type: boolean
+    description: Avoid sending CMD_PREFETCH_* commands to the SMMU.
+
+  cavium,cn9900-broken-page1-regspace:
+    type: boolean
+    description:
+      Replaces all page 1 offsets used for EVTQ_PROD/CONS, PRIQ_PROD/CONS
+      register access with page 0 offsets. Set for Cavium ThunderX2 silicon that
+      doesn't support SMMU page1 register space.
+
+required:
+  - compatible
+  - reg
+  - '#iommu-cells'
+
+additionalProperties: false
+
+examples:
+  - |+
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    iommu@2b400000 {
+            compatible = "arm,smmu-v3";
+            reg = <0x2b400000 0x20000>;
+            interrupts = <GIC_SPI 74 IRQ_TYPE_EDGE_RISING>,
+                         <GIC_SPI 75 IRQ_TYPE_EDGE_RISING>,
+                         <GIC_SPI 77 IRQ_TYPE_EDGE_RISING>,
+                         <GIC_SPI 79 IRQ_TYPE_EDGE_RISING>;
+            interrupt-names = "eventq", "priq", "cmdq-sync", "gerror";
+            dma-coherent;
+            #iommu-cells = <1>;
+            msi-parent = <&its 0xff0000>;
+    };