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

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Date:   Mon, 11 Apr 2022 17:11:04 +0200
From:   "Luca Weiss" <luca.weiss@...rphone.com>
To:     "Krzysztof Kozlowski" <krzysztof.kozlowski@...aro.org>,
        <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

Hi Krzysztof,

On Mon Apr 11, 2022 at 2:52 PM CEST, Krzysztof Kozlowski wrote:
> 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?

As these parameters are part of the dts downstream, I assume they differ
per board or actual LRA used.

But I also found other downstream dts examples on github (e.g.
awinic,aw8697_haptic) and they also seemed to use the same values for
these couple of registers (r_spare, tset and bstdbg). Maybe I can gather
more info but it's unlikely I'll be able to get a concrete answer..

Regards
Luca

>
> Best regards,
> Krzysztof