linux-kernel - Re: [PATCH 1/3] dt-bindings: iio: imu: mpu6050: Add level shifter

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Date:   Mon, 25 Sep 2023 14:21:57 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
CC:     Andreas Kemnade <andreas@...nade.info>, <jic23@...nel.org>,
        <lars@...afoo.de>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <conor+dt@...nel.org>,
        <bcousson@...libre.com>, <tony@...mide.com>,
        <jean-baptiste.maneyrol@....com>, <chenhuiz@...s.com>,
        <andy.shevchenko@...il.com>, <linux-iio@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-omap@...r.kernel.org>
Subject: Re: [PATCH 1/3] dt-bindings: iio: imu: mpu6050: Add level shifter

On Mon, 25 Sep 2023 14:24:32 +0200
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:

> On 25/09/2023 13:02, Andreas Kemnade wrote:
> > On Mon, 25 Sep 2023 11:28:52 +0100
> > Jonathan Cameron <Jonathan.Cameron@...wei.com> wrote:
> >   
> >> On Mon, 25 Sep 2023 08:54:08 +0200
> >> Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:
> >>  
> >>> On 25/09/2023 00:25, Andreas Kemnade wrote:    
> >>>> Found in ancient platform data struct:
> >>>> level_shifter: 0: VLogic, 1: VDD
> >>>>
> >>>> Signed-off-by: Andreas Kemnade <andreas@...nade.info>
> >>>> ---
> >>>>  .../devicetree/bindings/iio/imu/invensense,mpu6050.yaml         | 2 ++
> >>>>  1 file changed, 2 insertions(+)
> >>>>
> >>>> diff --git a/Documentation/devicetree/bindings/iio/imu/invensense,mpu6050.yaml b/Documentation/devicetree/bindings/iio/imu/invensense,mpu6050.yaml
> >>>> index 1db6952ddca5e..6aae2272fa15c 100644
> >>>> --- a/Documentation/devicetree/bindings/iio/imu/invensense,mpu6050.yaml
> >>>> +++ b/Documentation/devicetree/bindings/iio/imu/invensense,mpu6050.yaml
> >>>> @@ -48,6 +48,8 @@ properties:
> >>>>  
> >>>>    mount-matrix: true
> >>>>  
> >>>> +  invensense,level-shifter: true      
> >>>
> >>> It does not look like you tested the bindings, at least after quick
> >>> look. Please run `make dt_binding_check` (see
> >>> Documentation/devicetree/bindings/writing-schema.rst for instructions).
> >>> Maybe you need to update your dtschema and yamllint.
> >>>
> >>> Best regards,
> >>> Krzysztof
> >>>
> >>>     
> >>
> >> Also this one isn't obvious - give it a description in the binding doc.
> >>
> >> I'm not sure of the arguement for calling it level shift in general.
> >>  
> > I have no more descrption than the old source (see the citation from there)
> > https://invensense.tdk.com/wp-content/uploads/2015/02/MPU-9150-Register-Map.pdf  
> 
> I could not find any reference to level shift in this manual. To which
> page and part do you refer?
> 
> > 
> > does not list it. But that bit is needed to get things to work what also does the
> > vendor kernel do.
> > 
> > What could be a better descrption?  
> 
> I don't know, but something reasonable to you should be put there.

The text you have in the commit log seems better than nothing.
I suspect it's internally wiring VDD to VDDIO. Normally people just
connect both power supplies to same supply if they want to do that,
but maybe there was a chip variant that didn't have enough pins?

If you have the device, can you see it actually matches the packaging
types in the manual?

Jonathan

> 
> Best regards,
> Krzysztof
> 
>