linux-kernel - Re: [PATCH v2 1/3] dt-binding: aspeed: Add LPC PCC controller

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Message-ID: <e17cdf9d-ba96-41d2-9656-9e50d0e0795a@kernel.org>
Date: Mon, 10 Mar 2025 08:15:20 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Kevin Chen <kevin_chen@...eedtech.com>, "lee@...nel.org"
 <lee@...nel.org>, "robh@...nel.org" <robh@...nel.org>,
 "krzk+dt@...nel.org" <krzk+dt@...nel.org>,
 "conor+dt@...nel.org" <conor+dt@...nel.org>, "joel@....id.au"
 <joel@....id.au>, "andrew@...econstruct.com.au"
 <andrew@...econstruct.com.au>, "derek.kiernan@....com"
 <derek.kiernan@....com>, "dragan.cvetic@....com" <dragan.cvetic@....com>,
 "arnd@...db.de" <arnd@...db.de>,
 "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>,
 "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 Mo Elbadry <elbadrym@...gle.com>
Subject: Re: [PATCH v2 1/3] dt-binding: aspeed: Add LPC PCC controller

On 10/03/2025 02:50, Kevin Chen wrote:
>>> +        $ref: /schemas/types.yaml#/definitions/uint32-array
>>> +        description: The LPC I/O ports to pcc
>>
>> Description is too vague. Why would we encode I/O ports as some numbers
>> instead of GPIOs for example? If these are ports, why this is not a graph?
> For the port-mmaped I/O in x80 architecture, BMC need to handle specific port I/O in the relative HW module.
> So, I need to add the pcc-ports property as the snoop-ports property in Documentation/devicetree/bindings/mfd/aspeed-lpc.yaml
> 
>>
>> Missing constraints - min/maxItems, defaults, minimum/maximum etc.
> The port-mmaped I/O is defined from host, BMC as the device would capture the port I/O from the pcc-ports property defined in dts.

Put this information in the description, instead of copying property name.

> 
>>
>>> +
>>> +    required:
>>> +      - compatible
>>> +      - interrupts
>>> +      - pcc-ports
>>> +
>>>    "^uart-routing@[0-9a-f]+$":
>>>      $ref: /schemas/soc/aspeed/uart-routing.yaml#
>>>      description: The UART routing control under LPC register space @@
>>> -176,6 +205,13 @@ examples:
>>>          #size-cells = <1>;
>>>          ranges = <0x0 0x1e789000 0x1000>;
>>>
>>> +        lpc_pcc: lpc-pcc@0 {
>>> +            compatible = "aspeed,ast2600-lpc-pcc";
>>> +            reg = <0x0 0x140>;
>>> +            interrupts = <GIC_SPI 145 IRQ_TYPE_LEVEL_HIGH>;
>>> +            pcc-ports = <0x80>;
>>
>> So what 0x80 stands for?
> Host as x86 architecture would access the 0x80 port, which is mapped to the BMC PCC HW module.
> As a result, x86 can keep the port-mmaped I/O usage and access the BMC device, which is needed to know which port using in the PCC module in BMC.

And on different boards this is not 0x80?

Best regards,
Krzysztof