linux-kernel - Re: [PATCH v2 1/3] dt-bindings: i2c: Add RTL9300 I2C controller

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Message-ID: <e5954cb6-7889-40c4-82b0-6df95d09d54a@kernel.org>
Date: Tue, 24 Sep 2024 09:58:28 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Chris Packham <Chris.Packham@...iedtelesis.co.nz>
Cc: "andi.shyti@...nel.org" <andi.shyti@...nel.org>,
 "robh@...nel.org" <robh@...nel.org>, "krzk+dt@...nel.org"
 <krzk+dt@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>,
 "tsbogend@...ha.franken.de" <tsbogend@...ha.franken.de>,
 "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] dt-bindings: i2c: Add RTL9300 I2C controller

On 23/09/2024 23:09, Chris Packham wrote:
> Hi Krzyzstof,
> 
> On 23/09/24 08:25, Krzysztof Kozlowski wrote:
>> On Fri, Sep 20, 2024 at 12:09:28PM +1200, Chris Packham wrote:
>>> Add dtschema for the I2C controller on the RTL9300 SoC. The I2C
>>> controllers on this SoC are part of the "switch" block which is
>>> represented here as a syscon node. The SCL pins are dependent on the I2C
>>> controller (GPIO8 for the first controller, GPIO 17 for the second). The
>>> SDA pins can be assigned to either one of the I2C controllers (but not
>>> both).
>>>
>>> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
>>> ---
>>>
>>> Notes:
>>>      Changes in v2:
>>>      - Use reg property for controller registers
>>>      - Remove global-control-offset (will be hard coded in driver)
>>>      - Integrated the multiplexing function. Child nodes now represent the
>>>        available SDA lines
>>>
>>>   .../bindings/i2c/realtek,rtl9300-i2c.yaml     | 82 +++++++++++++++++++
>>>   MAINTAINERS                                   |  6 ++
>>>   2 files changed, 88 insertions(+)
>>>   create mode 100644 Documentation/devicetree/bindings/i2c/realtek,rtl9300-i2c.yaml
>>>
>>> diff --git a/Documentation/devicetree/bindings/i2c/realtek,rtl9300-i2c.yaml b/Documentation/devicetree/bindings/i2c/realtek,rtl9300-i2c.yaml
>>> new file mode 100644
>>> index 000000000000..e8c37239b299
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/i2c/realtek,rtl9300-i2c.yaml
>>> @@ -0,0 +1,82 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://scanmail.trustwave.com/?c=20988&d=2_3w5qdKawcvw7Bv6K3mA_v4JF1rlxddN3AhCekStg&u=http%3a%2f%2fdevicetree%2eorg%2fschemas%2fi2c%2frealtek%2crtl9300-i2c%2eyaml%23
>>> +$schema: http://scanmail.trustwave.com/?c=20988&d=2_3w5qdKawcvw7Bv6K3mA_v4JF1rlxddNyJxDbgXsw&u=http%3a%2f%2fdevicetree%2eorg%2fmeta-schemas%2fcore%2eyaml%23
>>> +
>>> +title: Realtek RTL I2C Controller
>>> +
>>> +maintainers:
>>> +  - Chris Packham <chris.packham@...iedtelesis.co.nz>
>>> +
>>> +description:
>>> +  The RTL9300 SoC has two I2C controllers. Each of these has an SCL line (which
>>> +  if not-used for SCL can be a GPIO). There are 8 common SDA lines that can be
>>> +  assigned to either I2C controller.
>>> +
>>> +properties:
>>> +  compatible:
>>> +    const: realtek,rtl9300-i2c
>>> +
>>> +  reg:
>>> +    description: Register offset and size this I2C controller.
>>> +
>>> +patternProperties:
>>> +  '^i2c@[0-7]$':
>>> +    $ref: /schemas/i2c/i2c-controller.yaml
>>> +    unevaluatedProperties: false
>>> +
>>> +    properties:
>>> +      reg:
>>> +        description: The SDA pin associated with the I2C bus.
>>> +        maxItems: 1
>>> +
>>> +    required:
>>> +      - reg
>>> +
>>> +unevaluatedProperties: false
>> This goes after "required:" block.
> Ack.
>>> +
>>> +required:
>>> +  - compatible
>>> +  - reg
>>> +
>>> +examples:
>>> +  - |
>>> +    switch@...00000 {
>>> +      compatible = "realtek,rtl9302c-switch", "syscon", "simple-mfd";
>> Drop... or put entire example in the parent device node.
> 
> OK I'll drop it.
> 
>>
>>> +      reg = <0x1b000000 0x10000>;
>>> +      #address-cells = <1>;
>>> +      #size-cells = <1>;
>>> +
>>> +      i2c@36c {
>>> +        compatible = "realtek,rtl9300-i2c";
>> Parent is 9302c, but this is 9300?
> 
> The RTL9302C is one of a series of switch chips with integrated CPUs. 
> There is also the RTL9301, RTL9302B and RTL9303 (there my be others but 
> those are the 4 I know about). The differences are all around the switch 
> port/SERDES. The documentation uses "RTL9300" when referring to things 
> common across the family. There's even an app note titled 
> "RTL9300_I2C_Application_Note_V1.1(83)". So I'd really like to use 
> "rtl9300" when talking about the SoC peripherals but use the specific 
> chip compatible when talking about the Ethernet switch or the overall 
> chip. I'm also tempted to add the other variants to my other in-flight 
> patch series.

Using family variant alone is in general not accepted. You need SoC
specific compatible in the front.

> 
> "realtek,rtl9300-i2c" also happens to be what openwrt is using, but I'm 
> not sure that that helps my argument as the binding is now quite different.

Does not matter. They could be using
"realtek,we-like-to-use-whatever-we-invented-soc", but that does not
mean we should accept it.

Best regards,
Krzysztof