linux-kernel - Re: [PATCH 3/3] dt-bindings: PCI: ti,j721e-pci-host: Add support for J722S SoC

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Message-ID: <a3548cfc-ca20-4f55-990c-097cc68e9750@ti.com>
Date: Wed, 17 Jan 2024 17:11:16 +0530
From: Siddharth Vadapalli <s-vadapalli@...com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
CC: <bhelgaas@...gle.com>, <lpieralisi@...nel.org>, <kw@...ux.com>,
        <robh@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <conor+dt@...nel.org>, <linux-pci@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <vigneshr@...com>,
        <afd@...com>, <srk@...com>, <s-vadapalli@...com>
Subject: Re: [PATCH 3/3] dt-bindings: PCI: ti,j721e-pci-host: Add support for
 J722S SoC



On 17/01/24 17:05, Krzysztof Kozlowski wrote:
> On 17/01/2024 12:24, Siddharth Vadapalli wrote:
>>
>>
>> On 17/01/24 16:06, Krzysztof Kozlowski wrote:
>>> On 17/01/2024 11:25, Siddharth Vadapalli wrote:
>>>> TI's J722S SoC has one instance of a Gen3 Single Lane PCIe controller.
>>>> The controller on J722S SoC is similar to the one present on TI's AM64
>>>> SoC, with the difference being that the controller on AM64 SoC supports
>>>> up to Gen2 link speed while the one on J722S SoC supports Gen3 link speed.
>>>>
>>>> Update the bindings with a new compatible for J722S SoC and enforce checks
>>>> for "num-lanes" and "max-link-speed".
>>>>
>>>> Technical Reference Manual of J722S SoC: https://www.ti.com/lit/zip/sprujb3
>>>>
>>>> Signed-off-by: Siddharth Vadapalli <s-vadapalli@...com>
>>>> ---
>>>>  .../devicetree/bindings/pci/ti,j721e-pci-host.yaml  | 13 +++++++++++++
>>>>  1 file changed, 13 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/pci/ti,j721e-pci-host.yaml b/Documentation/devicetree/bindings/pci/ti,j721e-pci-host.yaml
>>>> index 005546dc8bd4..b7648f7e73c9 100644
>>>> --- a/Documentation/devicetree/bindings/pci/ti,j721e-pci-host.yaml
>>>> +++ b/Documentation/devicetree/bindings/pci/ti,j721e-pci-host.yaml
>>>> @@ -14,6 +14,7 @@ properties:
>>>>    compatible:
>>>>      oneOf:
>>>>        - const: ti,j721e-pcie-host
>>>> +      - const: ti,j722s-pcie-host
>>>>        - const: ti,j784s4-pcie-host
>>>>        - description: PCIe controller in AM64
>>>>          items:
>>>> @@ -134,6 +135,18 @@ allOf:
>>>>            minimum: 1
>>>>            maximum: 4
>>>>  
>>>> +  - if:
>>>> +      properties:
>>>> +        compatible:
>>>> +          items:
>>>
>>> enum
>>>
>>>> +            - const: ti,j722s-pcie-host
>>>> +    then:
>>>> +      properties:
>>>> +        max-link-speed:
>>>> +          const: 3
>>>> +        num-lanes:
>>>> +          const: 1
>>>
>>> Similarly to previous patch: What is the point of all this? You have
>>> direct mapping compatible-property, so encode these in the drivers.
>>
>> Ok. I will drop patches 1 and 2 of this series and only post v2 of this patch
>> for adding a new compatible for J722S SoC without any checks for
>> "max-link-speed" or "num-lanes" for the new compatible.
> 
> Without driver change? So how does it solve my comment. I want to move
> all these unnecessary properties to the driver.

Driver support for verifying "num-lanes" is already present. I meant to say that
I will drop the checks in bindings in the v2 patch since "num-lanes" is verified
in driver too. However, "max-link-speed" is not verified either in the driver or
in the bindings prior to this series.

-- 
Regards,
Siddharth.