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SubjectRe: [PATCH 1/3] dt-bindings: PCI: cadence: Deprecate inbound/outbound specific bindings
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Hi Rob,

On 3/30/2020 9:31 PM, Rob Herring wrote:
> 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@ti.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@cadence.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@cadence.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.

For every buffer given by the host, we have to create a new outbound
translation. If there are no outbound regions, we have to report the error to
the endpoint function driver. At-least for reporting the error, we'd need to
have this binding no?
>
> 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.

I'm not sure if we should ever try to write to a non-existent register though
the behavior could be different in different platforms. IMHO maximum number of
outbound regions is a HW property and is best described in device tree.

Thanks
Kishon

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