Re: [RFC PATCH v2 1/6] Documentation: DT: Add entry for CDX controller

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 17/08/2022 18:05, Nipun Gupta wrote:
> This patch adds a devicetree binding documentation for CDX
> controller.
> 
Does not look like you tested the bindings. Please run `make
dt_binding_check` (see
Documentation/devicetree/bindings/writing-schema.rst for instructions).

> CDX bus controller dynamically detects CDX bus and the
> devices on these bus using CDX firmware.
> 
> Signed-off-by: Nipun Gupta <nipun.gupta@amd.com>

Use subject perfixes matching the subsystem (git log --oneline -- ...).

> ---
>  .../devicetree/bindings/bus/xlnx,cdx.yaml     | 108 ++++++++++++++++++
>  MAINTAINERS                                   |   6 +
>  2 files changed, 114 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/bus/xlnx,cdx.yaml
> 
> diff --git a/Documentation/devicetree/bindings/bus/xlnx,cdx.yaml b/Documentation/devicetree/bindings/bus/xlnx,cdx.yaml
> new file mode 100644
> index 000000000000..4247a1cff3c1
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/bus/xlnx,cdx.yaml
> @@ -0,0 +1,108 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/misc/xlnx,cdx.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Xilinx CDX bus controller
> +
> +description: |
> +  CDX bus controller for Xilinx devices is implemented to

You need to describe what is this CDX bus. Google says nothing...

> +  dynamically detect CDX bus and devices on these bus using the
> +  firmware. The CDX bus manages multiple FPGA based hardware
> +  devices, which can support network, crypto or any other specialized
> +  type of device. These FPGA based devices can be added/modified
> +  dynamically on run-time.
> +
> +  All devices on the CDX bus will have a unique streamid (for IOMMU)
> +  and a unique device ID (for MSI) corresponding to a requestor ID
> +  (one to one associated with the device). The streamid and deviceid
> +  are used to configure SMMU and GIC-ITS respectively.
> +
> +  iommu-map property is used to define the set of stream ids
> +  corresponding to each device and the associated IOMMU.
> +
> +  For generic IOMMU bindings, see:
> +  Documentation/devicetree/bindings/iommu/iommu.txt.

Drop sentence.

> +
> +  For arm-smmu binding, see:
> +  Documentation/devicetree/bindings/iommu/arm,smmu.yaml.

Drop sentence.

> +
> +  The MSI writes are accompanied by sideband data (Device ID).
> +  The msi-map property is used to associate the devices with the
> +  device ID as well as the associated ITS controller.
> +
> +  For generic MSI bindings, see:
> +  Documentation/devicetree/bindings/interrupt-controller/msi.txt.

Drop sentence.

> +
> +  For GICv3 and GIC ITS bindings, see:
> +  Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.yaml.

Drop sentence.

> +
> +maintainers:
> +  - Nipun Gupta <nipun.gupta@amd.com>
> +  - Nikhil Agarwal <nikhil.agarwal@amd.com>
> +
> +properties:
> +  compatible:
> +    const: "xlnx,cdxbus-controller-1.0"

No quotes.

> +
> +  reg:
> +    description: |
> +      specifies the CDX firmware region shared memory accessible by the
> +      ARM cores.

You need to describe the items instead (e.g. maxItems:1).

> +
> +  iommu-map:
> +    description: |
> +      Maps device Requestor ID to a stream ID and associated IOMMU. The
> +      property is an arbitrary number of tuples of
> +      (rid-base,iommu,streamid-base,length).
> +
> +      Any Requestor ID i in the interval [rid-base, rid-base + length) is
> +      associated with the listed IOMMU, with the iommu-specifier
> +      (i - streamid-base + streamid-base).

You need type and constraints.

> +
> +  msi-map:
> +    description:
> +      Maps an Requestor ID to a GIC ITS and associated msi-specifier
> +      data (device ID). The property is an arbitrary number of tuples of
> +      (rid-base,gic-its,deviceid-base,length).
> +
> +      Any Requestor ID in the interval [rid-base, rid-base + length) is
> +      associated with the listed GIC ITS, with the msi-specifier
> +      (i - rid-base + deviceid-base).

You need type and constraints.


> +
> +required:
> +  - compatible
> +  - reg
> +  - iommu-map
> +  - msi-map
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    smmu@ec000000 {
> +        compatible = "arm,smmu-v3";
> +        #iommu-cells = <1>;
> +        ...

???

> +
> +    gic@e2000000 {
> +        compatible = "arm,gic-v3";
> +        interrupt-controller;
> +        ...
> +        its: gic-its@e2040000 {
> +            compatible = "arm,gic-v3-its";
> +            msi-controller;
> +            ...
> +        }
> +    };
> +
> +    cdxbus: cdxbus@@4000000 {

Node names should be generic, so "cdx"

https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation

Drop the label.


> +        compatible = "xlnx,cdxbus-controller-1.0";
> +        reg = <0x00000000 0x04000000 0 0x1000>;
> +        /* define map for RIDs 250-259 */
> +        iommu-map = <250 &smmu 250 10>;
> +        /* define msi map for RIDs 250-259 */
> +        msi-map = <250 &its 250 10>;
> +    };
Best regards,
Krzysztof