linux-kernel - Re: [PATCH 1/2] dt-bindings: counter: Add new ti,omap-dmtimer-cap compatible

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Message-ID: <20fd5c31-eb37-4f48-9774-62a05f416bab@ti.com>
Date: Tue, 7 Oct 2025 15:19:33 +0530
From: Gokul Praveen <g-praveen@...com>
To: Krzysztof Kozlowski <krzk@...nel.org>, <j-keerthy@...com>,
        <vigneshr@...com>, <wbg@...nel.org>, <linux-kernel@...r.kernel.org>,
        <robh@...nel.org>, <krzk+dt@...nel.org>, <conor+dt@...nel.org>,
        <devicetree@...r.kernel.org>
CC: <u-kumar1@...com>, <n-francis@...com>, Gokul Praveen <g-praveen@...com>
Subject: Re: [PATCH 1/2] dt-bindings: counter: Add new ti,omap-dmtimer-cap
 compatible

Hi Krzysztof,

On 07/10/25 15:09, Krzysztof Kozlowski wrote:
> On 07/10/2025 18:23, Gokul Praveen wrote:
>> Hi Krzysztof,
>>
>>
>> On 07/10/25 12:05, Krzysztof Kozlowski wrote:
>>> On 26/09/2025 18:06, Gokul Praveen wrote:
>>>>>
>>>>>> +
>>>>>> +  ti,timers:
>>>>>> +    description: Timer instance phandle for the Capture
>>>>>
>>>>> So the only resource is phandle? That's completely fake device then. NAK.
>>>>>
>>>>
>>>>
>>>> The OMAP Timer IP can operate in 3 modes: Timer, PWM mode or capture
>>>> (mutually exclusive).
>>>> The timer/ti,timer-dm.yaml file describes the timer mode of operation.
>>>> It encapsulates base IP block and reg property is also part the same
>>>> binding.
>>>>
>>>> This node represents the capture mode with phandle reference to the
>>>> timer DT node. This is modeled all the same lines as how PWM
>>>> functionality is implemented in pwm/ti,omap-dmtimer-pwm.yaml
>>>
>>> Different modes do not have their own device nodes. It is still one
>>> device, so one device node.
>>>
>>>>
>>>> Now, if this needs to change, please suggest alternate.
>>>>
>>>> One solution is perhaps to add a new property to ti,timer-dm.yaml itself
>>>> to indicate the mode of IP?
>>>
>>> Not sure, depends what this really is and how it is used. I can also
>>> imagine that consumer defines the mod of operation.
>>>
>>
>> For a timer operating in capture mode, there are no consumers actually
>> and the only way we use it is through sysfs.
>>
>> Would it be good enough if I have a separate "mode" property for the
>> dmtimer device node just like how it is done for USB as follows where
>> the usb device node has a "dr_mode" property to decide on whether the
>> usb should act in host, device or otg mode.
> 
> 
> No, because of all my other comments in previous email.
> 
> 
Will having a separate sysfs property for enabling capture mode in 
dmtimer be a viable solution, which will then eliminate the need for a 
device tree property?

It would be great to hear your feedback on this, krzysztof.

Best regards
Gokul

> Best regards,
> Krzysztof