linux-kernel - Re: [PATCH v6 1/7] dt-bindings: i2c: xiic: make clocks optional

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Message-ID: <5dc423be-c1f4-4a59-abcc-807f63b25f3f@amd.com>
Date: Wed, 28 Jan 2026 16:00:30 +0100
From: Michal Simek <michal.simek@....com>
To: Andy Shevchenko <andriy.shevchenko@...el.com>,
 Andrew Lunn <andrew@...n.ch>
Cc: Krzysztof Kozlowski <krzk@...nel.org>,
 Abdurrahman Hussain <abdurrahman@...thop.ai>,
 Andi Shyti <andi.shyti@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, info@...ean-labs.com,
 linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org,
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v6 1/7] dt-bindings: i2c: xiic: make clocks optional



On 1/28/26 15:45, Andy Shevchenko wrote:
> On Wed, Jan 28, 2026 at 03:34:02PM +0100, Andrew Lunn wrote:
>> On Wed, Jan 28, 2026 at 12:21:41PM +0100, Michal Simek wrote:
>>> On 1/28/26 11:37, Krzysztof Kozlowski wrote:
>>>> On Tue, Jan 27, 2026 at 09:03:55PM +0000, Abdurrahman Hussain wrote:
>>>>> The xiic driver is designed to operate without explicit clock configuration
>>>>
>>>> And if you change this in the driver, then you change bindings?
>>>>
>>>> You miss here explanation based on hardware - how does the hardware work
>>>> if nothing ticks it clocks?
>>>
>>> Hardware obviously have clock input which needs to be connected. Without it
>>> it won't work.
>>
>> Should ACPI potential limitations be making the DT description less
>> accurate?
>>
>> Would it not be better that the driver has an DT binding and an ACPI
>> binding? Where there are common properties, common functions can be
>> used to retrieve them. However, if ACPI lacks usable clocks, use the
>> of_ method to get the clock from DT, and skip it for ACPI.
> 
> Why should we use of_ methods? If this is required we can check the type of
> fwnode and act accordingly, but I think this should go deeper into some
> treewide available helpers, because now some drivers repeat the mantra.
> 
> But how do the driver get the clock frequency (if needed for some register
> settings and/or calculations)? DT seems to have well established property
> 'clock-frequency' for that. Can we consider it as "ACPI binding" as well?

"clock-frequency" property in i2c is used for selecting i2c speed 100/400kHz.

Clock frequency in this driver is about describing clock coming to IP itself.
Documentation/devicetree/bindings/i2c/xlnx,xps-iic-2.00.a.yaml

Thanks,
Michal