Re: [PATCH 1/4] dt-bindings: input: Add binding for Qualcomm SPMI PMIC haptics

[Krzysztof Kozlowski <krzk@kernel.org>]

On 17/06/2026 13:02, Fenglin Wu wrote:
> 
> On 6/17/2026 6:35 PM, Krzysztof Kozlowski wrote:
>> On Tue, Jun 16, 2026 at 03:08:24AM -0700, Fenglin Wu wrote:
>>> ....
>>> +
>>> +  qcom,lra-period-us:
>>> +    description:
>>> +      LRA actuator initial resonance period in microseconds
>>> +      (1,000,000 / resonant_freq_hz).  Used to configure T_LRA-based play
>>> +      rates and the auto-resonance zero-crossing window.
>> This does not feel like static characteristic. Isn't period depending on
>> intensity of vibration you want to have? Why would that be fixed per
>> board?
> 
> This period is specifically used for playbacks that require 
> auto-resonance to be enabled, which I referred to as "T_LRA-based" and 
> "auto-resonance zero-crossing window." It plays a key role in the 
> "DIRECT_PLAY" mode, which produces a constant vibration effect. To 
> adjust the vibration intensity during this constant effect, the hardware 
> does it by scaling the peak voltage of the driver signals, rather than 
> changing the frequency.

But maybe changing frequency runtime still would be useful?

What does the frequency depend on? IOW, how do you choose the value here
- based on some motor-part characteristics?

Best regards,
Krzysztof