linux-kernel - Re: [PATCH 03/19] dt-bindings: bus: add CDX bus controller device tree bindings

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Message-ID: <5ebee797-aa87-8db4-228c-dfe236ad32f8@linaro.org>
Date:   Tue, 17 Jan 2023 18:54:22 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Nipun Gupta <nipun.gupta@....com>, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, gregkh@...uxfoundation.org,
        rafael@...nel.org, eric.auger@...hat.com,
        alex.williamson@...hat.com, cohuck@...hat.com,
        song.bao.hua@...ilicon.com, mchehab+huawei@...nel.org,
        maz@...nel.org, f.fainelli@...il.com, jeffrey.l.hugo@...il.com,
        saravanak@...gle.com, Michael.Srba@...nam.cz, mani@...nel.org,
        yishaih@...dia.com, jgg@...pe.ca, jgg@...dia.com,
        robin.murphy@....com, will@...nel.org, joro@...tes.org,
        masahiroy@...nel.org, ndesaulniers@...gle.com,
        linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Cc:     okaya@...nel.org, harpreet.anand@....com, nikhil.agarwal@....com,
        michal.simek@....com, git@....com
Subject: Re: [PATCH 03/19] dt-bindings: bus: add CDX bus controller device
 tree bindings

On 17/01/2023 14:41, Nipun Gupta wrote:
> Add device tree bindings for CDX bus controller.

Subject: drop second/last, redundant "device tree bindings". The
"dt-bindings" prefix is already stating that these are bindings.

> 
> Signed-off-by: Nipun Gupta <nipun.gupta@....com>
> ---
>  .../bindings/bus/xlnx,cdxbus-controller.yaml  | 68 +++++++++++++++++++
>  MAINTAINERS                                   |  1 +
>  2 files changed, 69 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/bus/xlnx,cdxbus-controller.yaml
> 
> diff --git a/Documentation/devicetree/bindings/bus/xlnx,cdxbus-controller.yaml b/Documentation/devicetree/bindings/bus/xlnx,cdxbus-controller.yaml
> new file mode 100644
> index 000000000000..b2f186864021
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/bus/xlnx,cdxbus-controller.yaml
> @@ -0,0 +1,68 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/bus/xlnx,cdxbus-controller.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: AMD CDX bus controller
> +
> +description: |
> +  CDX bus controller for AMD devices is implemented to 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
> +  devices. 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.
> +
> +  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.
> +
> +  rproc property (xlnx,rproc) is used to identify the remote processor
> +  with which APU (Application Processor Unit) interacts to find out
> +  the bus and device configuration.
> +
> +maintainers:
> +  - Nipun Gupta <nipun.gupta@....com>
> +  - Nikhil Agarwal <nikhil.agarwal@....com>
> +
> +properties:
> +  compatible:
> +    const: xlnx,cdxbus-controller

This misses SoC specific compatible. Drop "bus" - redundant. I would
also say - drop controller - do you see any other devices with such
compatible naming? Use naming consistent with other devices in the
kernel. Just open some controllers - SPI, I2C etc. and look there.

> +
> +  iommu-map: true

No mask?

> +
> +  msi-map: true
> +
> +  xlnx,rproc:
> +    $ref: /schemas/types.yaml#/definitions/phandle
> +    description:
> +      phandle to the remoteproc_r5 rproc node using which APU interacts
> +      with remote processor.
> +
> +required:
> +  - compatible
> +  - iommu-map
> +  - msi-map
> +  - xlnx,rproc
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    cdxbus-controller {

Node names should be generic, so just cdx.
https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation

> +        compatible = "xlnx,cdxbus-controller";
> +        /* define map for RIDs 250-259 */
> +        iommu-map = <250 &smmu 250 10>;

Best regards,
Krzysztof