linux-kernel - Re: [PATCH v3 1/3] dt-bindings: i2c: Add RTL9300 I2C controller

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Message-ID: <775c8de3-a66d-43ee-8941-cc55741f54f7@kernel.org>
Date: Wed, 25 Sep 2024 09:19:02 +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 v3 1/3] dt-bindings: i2c: Add RTL9300 I2C controller

On 24/09/2024 23:11, Chris Packham wrote:
> 
> On 24/09/24 20:55, Krzysztof Kozlowski wrote:
>> On Tue, Sep 24, 2024 at 11:02:28AM +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 v3:
>>>      - Remove parent node in example
>>>      - put unevaluatedProperties after required
>>>      - Add #address-cells and #size-cells
>>>      
>>>      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     | 80 +++++++++++++++++++
>>>   MAINTAINERS                                   |  6 ++
>>>   2 files changed, 86 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..979ec22e81f1
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/i2c/realtek,rtl9300-i2c.yaml
>>> @@ -0,0 +1,80 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://scanmail.trustwave.com/?c=20988&d=gf7y5rgy9ER44HZptkkovLbVGtkYd7ByAz3K6PNPAw&u=http%3a%2f%2fdevicetree%2eorg%2fschemas%2fi2c%2frealtek%2crtl9300-i2c%2eyaml%23
>>> +$schema: http://scanmail.trustwave.com/?c=20988&d=gf7y5rgy9ER44HZptkkovLbVGtkYd7ByA2-a7KJKBg&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
>> This is confusing. It took me some minutes to understand that two I2Cs
>> in the example do not match what you wrote here. I got there only because
>> of your DTS. Your patchsets - sent separately and describing problem
>> incompletely - do not help.
>>
>> This is the binding for I2C, not for RTL9300 SoC.
>>
>>> +  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.
>> Nope, your reboot mode does not have reg. Either fix reboot mode driver
>> or this. Preferably reboot mode.
> 
> I'm not sure what you mean by this. The syscon-reboot binding doesn't 
> require a reg property and I can only find one in-tree dts 
> (turris1x.dts) that actually gives it a reg property.

But it could. It uses offset instead of reg for historical reasons, when
it was outside of syscon node. I propose to add there reg and oneOf
requiring either reg or offset. This way you will have only MMIO children.

Best regards,
Krzysztof