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

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Message-ID: <2de3151b-eedc-4209-8b20-53473cafacef@ti.com>
Date: Tue, 7 Oct 2025 14:53:46 +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>
Subject: Re: [PATCH 1/2] dt-bindings: counter: Add new ti,omap-dmtimer-cap
 compatible

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.

&usb0 {
	status = "okay";
	dr_mode = "host";
};


> Or mode of operation could be even configured runtime, thus not suitable
> for DT at all.
> 
> Best regards,
> Krzysztof