Re: [PATCH v3 20/23] dt-bindings: ata: ahci: Add Baikal-T1 AHCI SATA controller DT schema

[Rob Herring <robh@kernel.org>]

On Thu, May 12, 2022 at 02:18:07AM +0300, Serge Semin wrote:
> Baikal-T1 AHCI controller is based on the DWC AHCI SATA IP-core v4.10a
> with the next specific settings: two SATA ports, cascaded CSR access based
> on two clock domains (APB and AXI), selectable source of the reference
> clock (though stable work is currently available from the external source
> only), two reset lanes for the application and SATA ports domains. Other
> than that the device is fully compatible with the generic DWC AHCI SATA
> bindings.
> 
> Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
> 
> ---
> 
> Changelog v2:
> - Rename 'syscon' property to 'baikal,bt1-syscon'.
> - Drop macro usage from the example node.
> ---
>  .../bindings/ata/baikal,bt1-ahci.yaml         | 127 ++++++++++++++++++
>  1 file changed, 127 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/ata/baikal,bt1-ahci.yaml
> 
> diff --git a/Documentation/devicetree/bindings/ata/baikal,bt1-ahci.yaml b/Documentation/devicetree/bindings/ata/baikal,bt1-ahci.yaml
> new file mode 100644
> index 000000000000..7c2eae75434f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/ata/baikal,bt1-ahci.yaml
> @@ -0,0 +1,127 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/ata/baikal,bt1-ahci.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Baikal-T1 SoC AHCI SATA controller
> +
> +maintainers:
> +  - Serge Semin <fancer.lancer@gmail.com>
> +
> +description: |
> +  AHCI SATA controller embedded into the Baikal-T1 SoC is based on the
> +  DWC AHCI SATA v4.10a IP-core.
> +
> +allOf:
> +  - $ref: snps,dwc-ahci.yaml#
> +
> +properties:
> +  compatible:
> +    contains:
> +      const: baikal,bt1-ahci
> +
> +  clocks:
> +    items:
> +      - description: Peripheral APB bus clock source
> +      - description: Application AXI BIU clock
> +      - description: Internal SATA Ports reference clock
> +      - description: External SATA Ports reference clock
> +
> +  clock-names:
> +    items:
> +      - const: pclk
> +      - const: aclk
> +      - const: ref_int
> +      - const: ref_ext
> +
> +  resets:
> +    items:
> +      - description: Application AXI BIU domain reset
> +      - description: SATA Ports clock domain reset
> +
> +  reset-names:
> +    items:
> +      - const: arst
> +      - const: ref
> +
> +  baikal,bt1-syscon:
> +    $ref: /schemas/types.yaml#/definitions/phandle
> +    description:
> +      Phandle reference to the CCU system controller. It is required to
> +      switch between internal and external SATA reference clock sources.

Seems like the CCU system ctrlr should be a clock provider that provides 
'ref' clock and then assigned-clocks can be used to pick internal vs. 
external ref.

> +
> +  ports-implemented:
> +    maximum: 0x3
> +
> +patternProperties:
> +  "^sata-port@[0-9a-e]$":
> +    type: object

       unevaluatedProperties: false

and then a $ref to a sata-port schema.

> +
> +    properties:
> +      reg:
> +        minimum: 0
> +        maximum: 1
> +
> +      snps,tx-ts-max:
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        description:
> +          Due to having AXI3 bus interface utilized the maximum Tx DMA
> +          transaction size can't exceed 16 beats (AxLEN[3:0]).
> +        minimum: 1
> +        maximum: 16
> +
> +      snps,rx-ts-max:
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        description:
> +          Due to having AXI3 bus interface utilized the maximum Rx DMA
> +          transaction size can't exceed 16 beats (AxLEN[3:0]).

That's not a per port limitation (even though it's a per port register)? 
I think this should be implied by the compatible string.

Really, firmware should configure this IMO.

> +        minimum: 1
> +        maximum: 16
> +
> +required:
> +  - compatible
> +  - reg
> +  - interrupts
> +  - clocks
> +  - clock-names
> +  - resets
> +  - baikal,bt1-syscon
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    sata@1f050000 {
> +      compatible = "baikal,bt1-ahci", "snps,dwc-ahci";
> +      reg = <0x1f050000 0x2000>;
> +      #address-cells = <1>;
> +      #size-cells = <0>;
> +
> +      interrupts = <0 64 4>;
> +
> +      clocks = <&ccu_sys 1>, <&ccu_axi 2>, <&ccu_sys 0>, <&clk_sata>;
> +      clock-names = "pclk", "aclk", "ref_int", "ref_ext";
> +
> +      resets = <&ccu_axi 2>, <&ccu_sys 0>;
> +      reset-names = "arst", "ref";
> +
> +      baikal,bt1-syscon = <&syscon>;
> +
> +      ports-implemented = <0x3>;
> +
> +      sata-port@0 {
> +        reg = <0>;
> +
> +        snps,tx-ts-max = <4>;
> +        snps,rx-ts-max = <4>;
> +      };
> +
> +      sata-port@1 {
> +        reg = <1>;
> +
> +        snps,tx-ts-max = <4>;
> +        snps,rx-ts-max = <4>;
> +      };
> +    };
> +...
> -- 
> 2.35.1
> 
>