[3/6] dt-bindings: riscv: convert cpu binding to json-schema

At Rob's request, we're starting to migrate our DT binding
documentation to json-schema YAML format.  Start by converting our cpu
binding documentation.  While doing so, document more properties and
nodes.  This includes adding binding documentation support for the E51
and U54 CPU cores ("harts") that are present on this SoC.  These cores
are described in:

    https://static.dev.sifive.com/FU540-C000-v1.0.pdf

This cpus.yaml file is intended to be a starting point and to
evolve over time.  It passes dt-doc-validate as of the yaml-bindings
commit 4c79d42e9216.

This patch was originally based on the ARM json-schema binding
documentation as added by commit 672951cbd1b7 ("dt-bindings: arm: Convert
cpu binding to json-schema").

Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-riscv@lists.infradead.org
---
 .../devicetree/bindings/riscv/cpus.yaml       | 274 ++++++++++++++++++
 1 file changed, 274 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/riscv/cpus.yaml

On Thu, Apr 11, 2019 at 3:43 AM Paul Walmsley <paul.walmsley@sifive.com> wrote:
>
> At Rob's request, we're starting to migrate our DT binding
> documentation to json-schema YAML format.  Start by converting our cpu
> binding documentation.  While doing so, document more properties and
> nodes.  This includes adding binding documentation support for the E51
> and U54 CPU cores ("harts") that are present on this SoC.  These cores
> are described in:
>
>     https://static.dev.sifive.com/FU540-C000-v1.0.pdf
>
> This cpus.yaml file is intended to be a starting point and to
> evolve over time.  It passes dt-doc-validate as of the yaml-bindings
> commit 4c79d42e9216.
>
> This patch was originally based on the ARM json-schema binding
> documentation as added by commit 672951cbd1b7 ("dt-bindings: arm: Convert
> cpu binding to json-schema").
>
> Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
> Signed-off-by: Paul Walmsley <paul@pwsan.com>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Cc: devicetree@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-riscv@lists.infradead.org
> ---
>  .../devicetree/bindings/riscv/cpus.yaml       | 274 ++++++++++++++++++
>  1 file changed, 274 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/riscv/cpus.yaml
>
> diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
> new file mode 100644
> index 000000000000..11ade807fd49
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
> @@ -0,0 +1,274 @@
> +# SPDX-License-Identifier: GPL-2.0
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/riscv/cpus.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: RISC-V bindings for 'cpus' DT nodes
> +
> +maintainers:
> +  - Paul Walmsley <paul.walmsley@sifive.com>
> +  - Palmer Dabbelt <palmer@sifive.com>
> +
> +description: |+
> +  In SoC device tree data files, the layout of CPUs is described in
> +  the "cpus" node.   This node in turn contains a number of subnodes
> +  representing CPUs, which define properties for every cpu.
> +
> +  Bindings for CPU nodes follow the Devicetree Specification, available from:
> +
> +  https://www.devicetree.org/specifications/
> +
> +  with updates for RISC-V cores provided in this document.
> +
> +  ================================
> +  Convention used in this document
> +  ================================
> +
> +  This document follows the conventions described in the Devicetree
> +  Specification, with the addition:
> +
> +  - square brackets define bitfields, e.g. reg[7:0] represents the
> +    value of the bitfield in the reg property contained in bits 7 down
> +    to 0
> +
> +  =====================================
> +  cpus and cpu node bindings definition
> +  =====================================
> +
> +  If a Devicetree file is used to provide hardware data to the kernel,
> +  the RISC-V architecture requires the cpus and cpu nodes to be
> +  present and contain the properties described below.
> +
> +properties:
> +  $nodename:
> +    const: cpus
> +    description: Container of cpu nodes
> +
> +  '#address-cells':
> +    const: 1
> +    description: |
> +      A single unsigned 32-bit integer uniquely identifies
> +      each RISC-V hart in a system.  (See the "reg" node under
> +      the "cpu" node, below).
> +
> +  '#size-cells':
> +    const: 0
> +
> +patternProperties:
> +  '^cpu@[0-9a-f]+$':
> +    properties:
> +      device_type:
> +        const: cpu
> +
> +      reg:
> +        maxItems: 1
> +        description: |
> +          Set the "reg" property to the hart ID of this CPU node.
> +          Each value in this property must be unique in the scope
> +          of the Devicetree file that contains it.
> +
> +      compatible:
> +        items:
> +          - const: riscv

Wrong order here. This should be last.

> +          - enum:
> +              - sifive,rocket0
> +              - sifive,e5
> +              - sifive,e51
> +              - sifive,u54-mc
> +              - sifive,u54
> +              - sifive,u5
> +        description: |
> +          Identifies that the hart uses the RISC-V instruction set
> +          and identifies the type of the hart.
> +
> +      mmu-type:
> +        items:
> +          - enum:

If a single value, then you can drop 'items'.

> +              - riscv,sv32
> +              - riscv,sv39
> +              - riscv,sv48
> +        description: |
> +          Identifies the MMU address translation mode used on this
> +          hart.  These values originate from the RISC-V Privileged
> +          Specification document, available from
> +          https://riscv.org/specifications/
> +
> +      riscv,isa:

This needs to have a $ref to a type schema. (Under an 'allOf' list
with this enum)

> +        items:
> +          - enum:

Also don't need items here if a single value.

> +              - rv64imac
> +              - rv64imafdc
> +        description: |
> +          Identifies the specific RISC-V instruction set architecture
> +          supported by the hart.  These are documented in the RISC-V
> +          User-Level ISA document, available from
> +          https://riscv.org/specifications/
> +
> +          The RISC-V Linux port only will execute on a subset of these

What Linux does isn't relevant to the binding.

> +          values.  However, other hart cores may be present in the
> +          Devicetree hardware description file that do not run Linux.
> +
> +      timebase-frequency:
> +        maxItems: 1

Not an array.

> +        description: |
> +          Specifies the clock frequency of the system timer in Hz.
> +          This value is common to all harts in this Linux system image.
> +
> +      i-cache-block-size:
> +        maxItems: 1

Not an array. Surely you can define either the set of possible values
or min/max values. Same comment on the rest of the cache props.

Are the cache attributes really not discoverable?

> +        description: |
> +          Specifies the size, in bytes, of an instruction cache line.
> +
> +      i-cache-sets:
> +        maxItems: 1
> +        description: |
> +          Specifies the number of sets in the hart's instruction cache.
> +
> +      i-cache-size:
> +        maxItems: 1
> +        description: |
> +          Specifies the size, in bytes, of the hart's instruction cache.
> +
> +      i-tlb-sets:
> +        maxItems: 1
> +        description: |
> +          Specifies the number of sets in the hart's instruction TLB.
> +          If present, the "tlb-split" property must be set.

'dependencies' can express this for you. We do need a core schema for
all these to define the type and maybe dependencies can be there.

> +
> +      i-tlb-size:
> +        maxItems: 1
> +        description: |
> +          Specifies the number of entries in the hart's instruction TLB.
> +          If present, the "tlb-split" property must be set.
> +
> +      d-cache-block-size:
> +        maxItems: 1
> +        description: |
> +          Specifies the size, in bytes, of a data cache line.
> +
> +      d-cache-sets:
> +        maxItems: 1
> +        description: |
> +          Specifies the number of sets in the hart's data cache.
> +
> +      d-cache-size:
> +        maxItems: 1
> +        description: |
> +          Specifies the size, in bytes, of the hart's data cache.
> +
> +      d-tlb-sets:
> +        maxItems: 1
> +        description: |
> +          Specifies the number of sets in the hart's data TLB.
> +          If present, the "tlb-split" property must be set.
> +
> +      d-tlb-size:
> +        maxItems: 1
> +        description: |
> +          Specifies the number of entries in the hart's data TLB.
> +          If present, the "tlb-split" property must be set.
> +
> +      tlb-split: true
> +
> +    patternProperties:
> +      '^interrupt-controller@[0-9a-f]+$':

No 'reg', so should not have a unit-address.

> +        properties:
> +          $nodename:

You don't need this as we just defined it above.

> +            const: interrupt-controller
> +            description: Describes the CPU's local interrupt controller
> +
> +          '#interrupt-cells':
> +            const: 1
> +
> +          compatible:
> +            const: riscv,cpu-intc
> +
> +          interrupt-controller: true
> +
> +        required:
> +          - '#interrupt-cells'
> +          - compatible
> +          - interrupt-controller
> +
> +    required:
> +      - device_type
> +      - reg
> +      - compatible
> +      - riscv,isa
> +      - timebase-frequency
> +
> +required:
> +  - '#address-cells'
> +  - '#size-cells'
> +
> +examples:
> +  - |
> +    // Example 1: SiFive Freedom U540G Development Kit
> +    cpus {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +        timebase-frequency = <1000000>;
> +        cpu@0 {
> +                clock-frequency = <0>;
> +                compatible = "sifive,rocket0", "riscv";
> +                device_type = "cpu";
> +                i-cache-block-size = <64>;
> +                i-cache-sets = <128>;
> +                i-cache-size = <16384>;
> +                reg = <0>;
> +                riscv,isa = "rv64imac";

> +                sifive,dtim = <&L8>;
> +                sifive,itim = <&L7>;

Not documented.

> +                status = "okay";

Don't show status in examples.

> +                L10: interrupt-controller {
> +                        #interrupt-cells = <1>;
> +                        compatible = "riscv,cpu-intc";
> +                        interrupt-controller;
> +                };
> +        };
> +        cpu@1 {
> +                clock-frequency = <0>;
> +                compatible = "sifive,rocket0", "riscv";
> +                d-cache-block-size = <64>;
> +                d-cache-sets = <64>;
> +                d-cache-size = <32768>;
> +                d-tlb-sets = <1>;
> +                d-tlb-size = <32>;
> +                device_type = "cpu";
> +                i-cache-block-size = <64>;
> +                i-cache-sets = <64>;
> +                i-cache-size = <32768>;
> +                i-tlb-sets = <1>;
> +                i-tlb-size = <32>;
> +                mmu-type = "riscv,sv39";
> +                reg = <1>;
> +                riscv,isa = "rv64imafdc";
> +                status = "okay";
> +                tlb-split;
> +                L13: interrupt-controller {
> +                        #interrupt-cells = <1>;
> +                        compatible = "riscv,cpu-intc";
> +                        interrupt-controller;
> +                };
> +        };
> +    };
> +
> +  - |
> +    // Example 2: Spike ISA Simulator with 1 Hart
> +    cpus {
> +            cpu@0 {
> +                    device_type = "cpu";
> +                    reg = <0>;
> +                    status = "okay";
> +                    compatible = "riscv";
> +                    riscv,isa = "rv64imafdc";
> +                    mmu-type = "riscv,sv48";
> +                    interrupt-controller {
> +                            #interrupt-cells = <1>;
> +                            interrupt-controller;
> +                            compatible = "riscv,cpu-intc";
> +                    };
> +            };
> +    };
> +...
> --
> 2.20.1
>