linux-kernel - Re: [PATCH 1/3] dt-bindings: input: Add bindings for Awinic AW8695 haptics

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Date:   Mon, 11 Apr 2022 14:52:26 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Luca Weiss <luca.weiss@...rphone.com>, linux-input@...r.kernel.org
Cc:     ~postmarketos/upstreaming@...ts.sr.ht, phone-devel@...r.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: input: Add bindings for Awinic AW8695
 haptics

On 11/04/2022 10:15, Luca Weiss wrote:

(...)

>>> +  awinic,f0-detection-play-time:
>>> +    $ref: /schemas/types.yaml#/definitions/uint32
>>> +    description: Drive waveform play times in the first period in the f0 detection
>>
>> Use standard unit suffixes for known units (e.g. time).
> 
> While the datasheet doesn't mention any time unit, the value is used to
> calculate the f0_trace_ms variable (which is milliseconds) but the
> result also depends on the awinic,f0-preset value, so it's not a raw
> time value.

I see, ok.

> 
>>
>>> +
>>> +  awinic,f0-detection-wait-time:
>>> +    $ref: /schemas/types.yaml#/definitions/uint32
>>> +    description: Waveform wait times in the f0 detection
>>
>> Ditto.
>>
>>> +
>>> +  awinic,f0-detection-repeat:
>>> +    $ref: /schemas/types.yaml#/definitions/uint32
>>> +    description: Repeat times in the f0 detection
>>> +
>>> +  awinic,f0-detection-trace:
>>> +    $ref: /schemas/types.yaml#/definitions/uint32
>>> +    description: Drive waveform play times in the second period and later in the f0 detection
>>> +
>>> +  awinic,boost-debug:
>>> +    $ref: /schemas/types.yaml#/definitions/uint8-array
>>> +    minItems: 3
>>> +    maxItems: 3
>>> +    description: Values for BSTDBG1-3 registers
>>
>> Do not encode device programming model (registers) into the binding. You
>> need to define it as a property related to hardware itself, not its
>> registers (e.g. boost value in mV).
> 
> Unfortunately I couldn't figure the meaning for this and the two values
> below.
> 
> The datasheet doesn't mention these registers at all and the downstream
> driver doesn't do anything meaningful with them (other than setting them)
> nor has any comment to indicate what they do.
> In the datasheet there's only BSTDBG4 mentioned where bits [5:1] mean
> PVDD output voltage setting so for these registers it could really be
> anthing :(
> 
> Maybe someone with more knowledge about LRAs might be able to decipher
> what tset and r_spare is at least? I unfortunately didn't manage.

Do you have to define them in such case in DT? Maybe it should be part
of driver?

Best regards,
Krzysztof