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

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Date:   Wed, 13 Feb 2019 10:34:25 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Loys Ollivier <lollivier@...libre.com>
Cc:     Johan Hovold <johan@...nel.org>, Rob Herring <robh@...nel.org>,
        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, Feb 11, 2019 at 03:06:50PM +0100, Loys Ollivier wrote:
> 
> 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>

> >> 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.

Sure, but a non-pulsing signal might have been easier to deal with if it
was meant to be used by software.

> > 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.

Let's go with that then.

Johan