linux-kernel - Re: [PATCH v3 2/4] dt-bindings: gnss: add mediatek binding

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Date:   Mon, 11 Feb 2019 15:06:50 +0100
From:   Loys Ollivier <lollivier@...libre.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     Rob Herring <robh@...nel.org>,
        Loys Ollivier <lollivier@...libre.com>,
        devicetree@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
        linux-kernel@...r.kernel.org, Kevin Hilman <khilman@...libre.com>,
        linux-amlogic@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: Re: [PATCH v3 2/4] dt-bindings: gnss: add mediatek binding


On Mon 11 Feb 2019 at 09:22, Johan Hovold <johan@...nel.org> wrote:

> On Wed, Jan 30, 2019 at 09:50:16AM -0600, Rob Herring wrote:
>> On Mon, Jan 28, 2019 at 05:37:59PM +0100, Loys Ollivier wrote:
>> > Add binding for Mediatek-based GNSS receivers.
>> > 
>> > Signed-off-by: Loys Ollivier <lollivier@...libre.com>
>> > ---
>> > 
>> > v3:
>> > Removed the I2C and SPI interfaces references.
>> > Removed the "mediatek,mt3339" compatible line.
>> > Added the optional propertied (reset, fix)
>> > Added the pin names for the optional properties.
>> > 
>> > v2:
>> > Renamed bindings from Globaltop/gtop to Mediatek/mtk.
>> > Moved current-speed as an optional propertie.
>> > Removed the status line in the example.
>> > Added "mediatek,mt3339" compatible.
>> > 
>> >  .../devicetree/bindings/gnss/mediatek.txt          | 37 ++++++++++++++++++++++
>> >  1 file changed, 37 insertions(+)
>> >  create mode 100644 Documentation/devicetree/bindings/gnss/mediatek.txt
>> > 
>> > diff --git a/Documentation/devicetree/bindings/gnss/mediatek.txt b/Documentation/devicetree/bindings/gnss/mediatek.txt
>> > new file mode 100644
>> > index 000000000000..00650d81c5c8
>> > --- /dev/null
>> > +++ b/Documentation/devicetree/bindings/gnss/mediatek.txt
>> > @@ -0,0 +1,37 @@
>> > +Mediatek-based GNSS Receiver DT binding
>> > +
>> > +Mediatek chipsets are used in GNSS-receiver modules produced by several
>> > +vendors and can use an UART interface.
>
> s/an/a/
>
ok

>> > +
>> > +Please see Documentation/devicetree/bindings/gnss/gnss.txt for generic
>> > +properties.
>> > +
>> > +Required properties:
>> > +
>> > +- compatible	: Must be
>> > +
>> > +			"globaltop,pa6h"
>> > +
>> > +- vcc-supply	: Main voltage regulator (pin name: VCC)
>> > +
>> > +Optional properties:
>> > +
>> > +- gtop,reset-gpios	: GPIO used to reset the device
>> > +  			  (pin name: RESET, NRESET)
>> 
>> reset-gpios is the standard name.
>> 
>> > +- gtop,fix-gpios	: GPIO used to determine device position fix state
>> > +			  (pin name: FIX, 3D_FIX)
>
> I'm thinking we might need a standard name for fix-gpios as well. This
> isn't a feature that is globaltop (or mediatek) specific, and other
> manufacturers provide similar functionality through pins named UI_FIX,
> or even LCKIND (lock indicator).
>
> The pin is typically used to drive an indicator LED AFAIU, but the
> characteristics of the signal varies from device to device (fw to fw),
> for example, pulse when no lock and low otherwise, or pulse when a 2d or
> 3d-fix is acquired, etc.
>

Yes most GNSS recevivers provide a similar feature even if behavior of
the line differs.

> I'm not sure how useful the pulsing would be for software, but someone
> might find a use for it in some form.
>

Well it is useful to know when you start acquiring "valid" positionning
data. I'm using this as a trigger to start recording position.

> Rob, is this something we want to keep in the binding, and if so, how
> about using a generic name such as "gnss-fix-gpios"?
>

Name "gnss-fix-gpios" sounds good to me.

Loys

> Johan


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