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

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Message-ID: <ab5c995c-b7b6-4435-9f6e-8b0e37add2e9@alliedtelesis.co.nz>
Date: Mon, 23 Sep 2024 21:09:29 +0000
From: Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To: Krzysztof Kozlowski <krzk@...nel.org>
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

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.

"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.

>
>> +        reg = <0x36c 0x14>;
>> +        clock-frequency = <100000>;
>> +        #address-cells = <1>;
>> +        #size-cells = <0>;
>> +
>> +        i2c@0 {
>> +          reg = <0>;
>> +          #address-cells = <1>;
>> +          #size-cells = <0>;
>> +          gpio@20 {
>> +              compatible = "nxp,pca9555";
> Mixed indentation.
Whoops missed that. Will fix.
>
>> +              gpio-controller;
>> +              #gpio-cells = <2>;
>> +              reg = <0x20>;
>> +          };
>> +        };
> Best regards,
> Krzysztof
>