linux-kernel - Re: [RESEND PATCH v7 1/2] dt-bindings: PCI: xilinx-cpm: Add `cpm_crx` and `cpm5nc_fw

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Message-ID: <4b741da1-6540-4e5c-aa32-098420cab3c2@kernel.org>
Date: Tue, 15 Apr 2025 07:34:22 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: "Musham, Sai Krishna" <sai.krishna.musham@....com>
Cc: "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
 "lpieralisi@...nel.org" <lpieralisi@...nel.org>, "kw@...ux.com"
 <kw@...ux.com>,
 "manivannan.sadhasivam@...aro.org" <manivannan.sadhasivam@...aro.org>,
 "robh@...nel.org" <robh@...nel.org>, "krzk+dt@...nel.org"
 <krzk+dt@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>,
 "cassel@...nel.org" <cassel@...nel.org>,
 "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "Simek, Michal" <michal.simek@....com>,
 "Gogada, Bharat Kumar" <bharat.kumar.gogada@....com>,
 "Havalige, Thippeswamy" <thippeswamy.havalige@....com>
Subject: Re: [RESEND PATCH v7 1/2] dt-bindings: PCI: xilinx-cpm: Add `cpm_crx`
 and `cpm5nc_fw_attr` properties

On 14/04/2025 14:23, Musham, Sai Krishna wrote:
> [AMD Official Use Only - AMD Internal Distribution Only]
> 
> Hi Krzysztof,
> 
> Thanks for the review.
> 
>> -----Original Message-----
>> From: Krzysztof Kozlowski <krzk@...nel.org>
>> Sent: Monday, April 14, 2025 12:32 PM
>> To: Musham, Sai Krishna <sai.krishna.musham@....com>
>> Cc: bhelgaas@...gle.com; lpieralisi@...nel.org; kw@...ux.com;
>> manivannan.sadhasivam@...aro.org; robh@...nel.org; krzk+dt@...nel.org;
>> conor+dt@...nel.org; cassel@...nel.org; linux-pci@...r.kernel.org;
>> devicetree@...r.kernel.org; linux-kernel@...r.kernel.org; Simek, Michal
>> <michal.simek@....com>; Gogada, Bharat Kumar
>> <bharat.kumar.gogada@....com>; Havalige, Thippeswamy
>> <thippeswamy.havalige@....com>
>> Subject: Re: [RESEND PATCH v7 1/2] dt-bindings: PCI: xilinx-cpm: Add `cpm_crx`
>> and `cpm5nc_fw_attr` properties
>>
>> Caution: This message originated from an External Source. Use proper caution
>> when opening attachments, clicking links, or responding.
>>
>>
>> On Mon, Apr 14, 2025 at 08:53:03AM GMT, Sai Krishna Musham wrote:
>>> Add the `cpm_crx` property to manage the PCIe IP reset, and
>>> `cpm5nc_fw_attr` property to clear firewall after link reset, while
>>> maintaining backward compatibility with existing device trees.
>>>
>>> Also, incorporate `reset-gpios` in example for GPIO-based handling of
>>> the PCIe Root Port (RP) PERST# signal for enabling assert and deassert
>>> control.
>>>
>>> The `reset-gpios` and `cpm_crx` properties must be provided for CPM,
>>> CPM5 and CPM5_HOST1. For CPM5NC, all three properties - `reset-gpios`,
>>> `cpm_crx` and `cpm5nc_fw_attr` must be explicitly defined to ensure
>>
>> This we see from the diff, but why they must be defined?
>>
>>> proper functionality.
>>
>> What functionality?
>>
> 
> For our controller, if cpm_crx is not provided lane errors will be observed.
> Specifically for CPM5NC, if cpm5nc_fw_attr property is not provided, the firewall
> is not cleared after reset and further PCIe transactions will not be allowed.
> Therefore, these properties must be defined.

This must be in the commit msg.

> 
>>>
>>> Include an example DTS node and complete the binding documentation for
>>> CPM5NC. Also, fix the bridge register address size in the example for
>>> CPM5.
>>>
>>> Signed-off-by: Sai Krishna Musham <sai.krishna.musham@....com>
>>> ---
>>> Changes for v7:
>>> - Update CPM5NC device tree binding.
>>> - Add CPM5NC device tree example node.
>>> - Update commit message.
>>>
>>> Changes for v6:
>>> - Resolve ABI break.
>>> - Update commit message.
>>>
>>
>> ...
>>
>>> +  - if:
>>> +      properties:
>>> +        compatible:
>>> +          contains:
>>> +            enum:
>>> +              - xlnx,versal-cpm5nc-host
>>> +    then:
>>> +      properties:
>>> +        reg:
>>> +          items:
>>> +            - description: CPM system level control and status registers.
>>> +            - description: Configuration space region and bridge registers.
>>> +            - description: CPM clock and reset control registers.
>>> +            - description: CPM5NC Firewall attribute register.
>>> +          minItems: 2
>>> +        reg-names:
>>> +          items:
>>> +            - const: cpm_slcr
>>> +            - const: cfg
>>> +            - const: cpm_crx
>>> +            - const: cpm5nc_fw_attr
>>> +          minItems: 2
>>
>> Why interrupts are not required for this variant? Why isn't this an
>> interrupt controller?
>>
> 
> MSI and MSI-X interrupts are handled via GIC, so msi-map property is
> required for interrupt handling.
> Legacy interrupt support is not available, and Error interrupt support will be
> added in future, once it is added corresponding DT changes will be added.

I don't think commit msg explained this.

> 



Best regards,
Krzysztof