linux-kernel - Re: [PATCH] arm: dts: gta04: add gps support

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Message-ID: <20190130090232.GL3691@localhost>
Date:   Wed, 30 Jan 2019 10:02:32 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Andreas Kemnade <andreas@...nade.info>
Cc:     Johan Hovold <johan@...nel.org>, bcousson@...libre.com,
        tony@...mide.com, robh+dt@...nel.org, mark.rutland@....com,
        linux-omap@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, letux-kernel@...nphoenux.org
Subject: Re: [PATCH] arm: dts: gta04: add gps support

On Mon, Jan 28, 2019 at 05:44:29PM +0100, Andreas Kemnade wrote:
> On Mon, 28 Jan 2019 08:53:56 +0100
> Johan Hovold <johan@...nel.org> wrote:
> 
> > On Fri, Jan 25, 2019 at 08:43:10PM +0100, Andreas Kemnade wrote:
> > > The GTA04 has a w2sg0004 or w2sg0084 gps chip. Not detectable
> > > which one is mounted so use the compatibility entry for w2sg0004
> > > for all which will work for both.
> > > 
> > > Signed-off-by: Andreas Kemnade <andreas@...nade.info>
> > > ---
> > > w2sg0004 bindings (together with the corresponding support is in
> > > https://git.kernel.org/pub/scm/linux/kernel/git/johan/gnss gnss-next)
> > >  arch/arm/boot/dts/omap3-gta04.dtsi | 13 +++++++++++++
> > >  1 file changed, 13 insertions(+)

> > > +	gps: gps {  
> > 
> > The node should be named "gnss" as per the binding.
> > 
> > > +		compatible = "wi2wi,w2sg0004";
> > > +		pinctrl-names = "default";
> > > +		pinctrl-0 = <&gps_pins>;
> > > +		sirf,onoff-gpios = <&gpio5 17 GPIO_ACTIVE_HIGH>;
> > > +		lna-supply = <&vsim>;  
> > 
> > Also, the vcc-supply is a required property.
> > 
> well, it is not require in the driver and it has different behavior
> (on even when not opened if on-off is there) than the lna-supply used
> here. So maybe fix the binding documentation?

The device-tree describes hardware, and how a particular driver happens
to implement a binding is not relevant.

That said, there is a bit of an on-going, shall we say philosophical,
debate about this. The regulator maintainer takes a firm position that
all mandatory physical supplies should be represented in firmware
	
	https://lore.kernel.org/lkml/20181123133126.GF2089@sirena.org.uk/T/#u
	https://lore.kernel.org/lkml/20180409102244.GB11532@sirena.org.uk/T/#u

while Rob appears to take a slightly different stance on fixed
regulators while admitting that this an issue which has not yet been
fully resolved:

	https://lore.kernel.org/lkml/20180425171123.xhyoay3nu463btoq@rob-hp-laptop/T/#u

Since this is a new binding, and the hardware requires the vcc supply
and this is reflected in the binding, I think you should add a fixed
regulator. At least until you hear otherwise. ;)

Johan