linux-kernel - Re: [PATCH 1/3] dt-bindings: PCI: cadence: Deprecate inbound/outbound specific bindings

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Date:   Mon, 30 Mar 2020 10:01:42 -0600
From:   Rob Herring <robh@...nel.org>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Tom Joseph <tjoseph@...ence.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Andrew Murray <amurray@...goodpenguin.co.uk>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Mark Rutland <mark.rutland@....com>, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: PCI: cadence: Deprecate
 inbound/outbound specific bindings

On Fri, Mar 27, 2020 at 04:17:25PM +0530, Kishon Vijay Abraham I wrote:
> Deprecate cdns,max-outbound-regions and cdns,no-bar-match-nbits for
> host mode as both these could be derived from "ranges" and "dma-ranges"
> property. "cdns,max-outbound-regions" property would still be required
> for EP mode.
> 
> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> ---
>  .../bindings/pci/cdns,cdns-pcie-ep.yaml       |  2 +-
>  .../bindings/pci/cdns,cdns-pcie-host.yaml     |  3 +--
>  .../devicetree/bindings/pci/cdns-pcie-ep.yaml | 25 +++++++++++++++++++
>  .../bindings/pci/cdns-pcie-host.yaml          | 10 ++++++++
>  .../devicetree/bindings/pci/cdns-pcie.yaml    |  8 ------
>  5 files changed, 37 insertions(+), 11 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/pci/cdns-pcie-ep.yaml
> 
> diff --git a/Documentation/devicetree/bindings/pci/cdns,cdns-pcie-ep.yaml b/Documentation/devicetree/bindings/pci/cdns,cdns-pcie-ep.yaml
> index 2996f8d4777c..50ce5d79d2c7 100644
> --- a/Documentation/devicetree/bindings/pci/cdns,cdns-pcie-ep.yaml
> +++ b/Documentation/devicetree/bindings/pci/cdns,cdns-pcie-ep.yaml
> @@ -10,7 +10,7 @@ maintainers:
>    - Tom Joseph <tjoseph@...ence.com>
>  
>  allOf:
> -  - $ref: "cdns-pcie.yaml#"
> +  - $ref: "cdns-pcie-ep.yaml#"
>    - $ref: "pci-ep.yaml#"
>  
>  properties:
> diff --git a/Documentation/devicetree/bindings/pci/cdns,cdns-pcie-host.yaml b/Documentation/devicetree/bindings/pci/cdns,cdns-pcie-host.yaml
> index cabbe46ff578..84a8f095d031 100644
> --- a/Documentation/devicetree/bindings/pci/cdns,cdns-pcie-host.yaml
> +++ b/Documentation/devicetree/bindings/pci/cdns,cdns-pcie-host.yaml
> @@ -45,8 +45,6 @@ examples:
>              #size-cells = <2>;
>              bus-range = <0x0 0xff>;
>              linux,pci-domain = <0>;
> -            cdns,max-outbound-regions = <16>;
> -            cdns,no-bar-match-nbits = <32>;
>              vendor-id = <0x17cd>;
>              device-id = <0x0200>;
>  
> @@ -57,6 +55,7 @@ examples:
>  
>              ranges = <0x02000000 0x0 0x42000000  0x0 0x42000000  0x0 0x1000000>,
>                       <0x01000000 0x0 0x43000000  0x0 0x43000000  0x0 0x0010000>;
> +            dma-ranges = <0x02000000 0x0 0x0 0x0 0x0 0x1 0x00000000>;
>  
>              #interrupt-cells = <0x1>;
>  
> diff --git a/Documentation/devicetree/bindings/pci/cdns-pcie-ep.yaml b/Documentation/devicetree/bindings/pci/cdns-pcie-ep.yaml
> new file mode 100644
> index 000000000000..6150a7a7bdbf
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pci/cdns-pcie-ep.yaml
> @@ -0,0 +1,25 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: "http://devicetree.org/schemas/pci/cdns-pcie-ep.yaml#"
> +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> +
> +title: Cadence PCIe Device
> +
> +maintainers:
> +  - Tom Joseph <tjoseph@...ence.com>
> +
> +allOf:
> +  - $ref: "cdns-pcie.yaml#"
> +
> +properties:
> +  cdns,max-outbound-regions:
> +    description: maximum number of outbound regions
> +    allOf:
> +      - $ref: /schemas/types.yaml#/definitions/uint32
> +    minimum: 1
> +    maximum: 32
> +    default: 32

I have a feeling that as the PCI endpoint binding evolves this won't be 
necessary. I can see a common need to define the number of BARs for an 
endpoint and then this will again just be error checking.

What's the result if you write to a non-existent region in register 
CDNS_PCIE_AT_OB_REGION_PCI_ADDR0/1? If the register is non-existent and 
doesn't abort, you could detect this instead.

Rob