Re: [PATCH v2 6/8] dt-bindings: firmware: arm,scpi: Convert to json schema

[Sudeep Holla <sudeep.holla@arm.com>]

On Wed, Jun 02, 2021 at 10:58:00AM -0500, Rob Herring wrote:
> On Tue, Jun 01, 2021 at 11:49:02PM +0100, Sudeep Holla wrote:
> > Convert the old text format binding for System Control and Power Interface
> > (SCPI) Message Protocol into the new and shiny YAML format.
> > 
> > Cc: Rob Herring <robh+dt@kernel.org>
> > Cc: Kevin Hilman <khilman@baylibre.com>
> > Cc: Neil Armstrong <narmstrong@baylibre.com>
> > Cc: Jerome Brunet <jbrunet@baylibre.com>
> > Cc: Viresh Kumar <viresh.kumar@linaro.org
> > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> > ---
> >  .../devicetree/bindings/arm/arm,scpi.txt      | 204 -------------
> >  .../bindings/firmware/arm,scpi.yaml           | 285 ++++++++++++++++++
> >  MAINTAINERS                                   |   2 +-
> >  3 files changed, 286 insertions(+), 205 deletions(-)
> >  delete mode 100644 Documentation/devicetree/bindings/arm/arm,scpi.txt
> >  create mode 100644 Documentation/devicetree/bindings/firmware/arm,scpi.yaml
> 
> [...]
> 
> > diff --git a/Documentation/devicetree/bindings/firmware/arm,scpi.yaml b/Documentation/devicetree/bindings/firmware/arm,scpi.yaml
> > new file mode 100644
> > index 000000000000..b44a5a7040fc
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/firmware/arm,scpi.yaml
> > @@ -0,0 +1,285 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +# Copyright 2021 ARM Ltd.
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/firmware/arm,scpi.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: System Control and Power Interface (SCPI) Message Protocol bindings
> > +
> > +maintainers:
> > +  - Sudeep Holla <sudeep.holla@arm.com>
> > +
> > +description: |
> > +  Firmware implementing the SCPI described in ARM document number ARM DUI
> > +  0922B ("ARM Compute Subsystem SCP: Message Interface Protocols")[0] can be
> > +  used by Linux to initiate various system control and power operations.
> > +
> > +  This binding is intended to define the interface the firmware implementing
> > +  the SCPI provide for OSPM in the device tree.
> > +
> > +  [0] http://infocenter.arm.com/help/topic/com.arm.doc.dui0922b/index.html
> > +
> > +properties:
> > +  $nodename:
> > +    const: scpi
> > +
> > +  compatible:
> > +    description: |
> > +      SCPI compliant firmware complying to SCPI v1.0 and above OR
> > +      SCPI compliant firmware complying to all unversioned releases
> > +      prior to SCPI v1.0
> > +    oneOf:
> > +      - const: arm,scpi               # SCPI v1.0 and above
> > +      - const: arm,scpi-pre-1.0       # Unversioned SCPI before v1.0
> > +
> > +  mboxes:
> > +    description: |
> > +      List of phandle and mailbox channel specifiers. All the channels reserved
> > +      by remote SCP firmware for use by SCPI message protocol should be
> > +      specified in any order.
> > +    minItems: 1
> > +
> > +  shmem:
> > +    description: |
> > +      List of phandle pointing to the shared memory(SHM) area between the
> > +      processors using these mailboxes for IPC, one for each mailbox SHM can
> > +      be any memory reserved for the purpose of this communication between the
> > +      processors.
> > +    minItems: 1
> > +
> > +additionalProperties:
> > +  type: object
> > +
> > +patternProperties:
> > +  "^(sensors|power-domains)(-[0-9a-f]+)?$":
> 
> AFAICT, we only ever have 1 sensor and 1 power-domains node, so we don't 
> need the numbering.
>

Right, I initially had clock too there and didn't notice the above 2 doesn't
need the numbering, will drop it.

> Also, these should each be their own entry rather that having the 
> if/then schema mess below. You need an 'additionalProperties: false' in 
> here too.
>

OK that sounds cleaner.

> > +    type: object
> > +    description: |
> > +      Each sub-node represents one of the controller - power domains or sensors.
> > +
> > +    properties:
> > +      compatible:
> > +        oneOf:
> > +          - const: arm,scpi-sensors
> > +          - const: arm,scpi-power-domains
> > +
> > +  "^clocks(-[0-9a-f]+)?$":
> > +    type: object
> > +    description: |
> > +      "arm,scpi-clocks" - This is the container node. Each sub-node
> > +      represents one of the types of clock controller - indexed or full range.
> > +
> > +      "arm,scpi-dvfs-clocks" - all the clocks that are variable and index
> > +      based. These clocks don't provide an entire range of values
> > +      between the limits but only discrete points within the range. The
> > +      firmware provides the mapping for each such operating frequency
> > +      and the index associated with it. The firmware also manages the
> > +      voltage scaling appropriately with the clock scaling.
> > +
> > +      "arm,scpi-variable-clocks" - all the clocks that are variable and
> > +      provide full range within the specified range. The firmware
> > +      provides the range of values within a specified range.
> > +
> > +    properties:
> > +      compatible:
> > +        oneOf:
> > +          - const: arm,scpi-clocks
> > +          - const: arm,scpi-dvfs-clocks
> > +          - const: arm,scpi-variable-clocks
> 
> This doesn't make sense. The first one is the parent node and the last 2 
> are child nodes under it. The child nodes need to be defined in yet 
> another level.
>

Agreed, I did that for SCMI regulators, will follow that here too.

> > +
> > +required:
> > +  - compatible
> > +  - mboxes
> > +  - shmem
> > +
> > +allOf:
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          contains:
> > +            const: arm,scpi-sensors
> > +    then:
> > +      properties:
> > +        '#thermal-sensor-cells':
> > +          const: 1
> > +
> > +      required:
> > +        - '#thermal-sensor-cells'
> > +
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          contains:
> > +            const: arm,scpi-power-domains
> > +    then:
> > +      properties:
> > +        '#power-domain-cells':
> > +          const: 1
> > +
> > +        num-domains:
> > +          $ref: /schemas/types.yaml#/definitions/uint32
> > +          description: |
> > +            Total number of power domains provided by SCPI. This is needed as
> > +            the SCPI message protocol lacks a mechanism to query this
> > +            information at runtime.
> > +
> > +      required:
> > +        - '#power-domain-cells'
> > +        - num-domains
> > +
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          contains:
> > +            enum:
> > +              - arm,scpi-dvfs-clocks
> > +              - arm,scpi-variable-clocks
> 
> This would never be true unless you removed the container 'clocks' node.
>

Understood. I should have tested removing properties in the example like
I did for SCMI. I must have show less interest for SCPI as it is old and
almost deprecated 😁. I will fix it.

-- 
Regards,
Sudeep

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