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Subject: Re: [Letux-kernel] [PATCH] arm: dts: gta04: add gps support
From:   "H. Nikolaus Schaller" <hns@goldelico.com>
In-Reply-To: <20190130090232.GL3691@localhost>
Date:   Wed, 30 Jan 2019 15:06:12 +0100
Cc:     Mark Rutland <mark.rutland@arm.com>,
        devicetree <devicetree@vger.kernel.org>,
        Tony Lindgren <tony@atomide.com>,
        Johan Hovold <johan@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Benoit Cousson <bcousson@baylibre.com>,
        linux-omap <linux-omap@vger.kernel.org>,
        Discussions about the Letux Kernel 
        <letux-kernel@openphoenux.org>
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References: <20190125194310.11170-1-andreas@kemnade.info> <20190128075356.GJ3691@localhost> <20190128163025.7daa385b@kemnade.info> <20190130090232.GL3691@localhost>
To:     Andreas Kemnade <andreas@kemnade.info>
Sender: linux-kernel-owner@vger.kernel.org
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Hi Andreas,

> Am 30.01.2019 um 10:02 schrieb Johan Hovold <johan@kernel.org>:
>=20
> 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@kernel.org> wrote:
>>=20
>>> 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.
>>>>=20
>>>> Signed-off-by: Andreas Kemnade <andreas@kemnade.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(+)
>=20
>>>> +	gps: gps { =20
>>>=20
>>> The node should be named "gnss" as per the binding.
>>>=20
>>>> +		compatible =3D "wi2wi,w2sg0004";
>>>> +		pinctrl-names =3D "default";
>>>> +		pinctrl-0 =3D <&gps_pins>;
>>>> +		sirf,onoff-gpios =3D <&gpio5 17 GPIO_ACTIVE_HIGH>;
>>>> +		lna-supply =3D <&vsim>; =20
>>>=20
>>> Also, the vcc-supply is a required property.
>>>=20
>> 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?
>=20
> The device-tree describes hardware, and how a particular driver =
happens
> to implement a binding is not relevant.
>=20
> 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
> =09
> 	=
https://lore.kernel.org/lkml/20181123133126.GF2089@sirena.org.uk/T/#u
> 	=
https://lore.kernel.org/lkml/20180409102244.GB11532@sirena.org.uk/T/#u
>=20
> 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:
>=20
> 	=
https://lore.kernel.org/lkml/20180425171123.xhyoay3nu463btoq@rob-hp-laptop=
/T/#u
>=20
> 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. ;)

Assuming that there is no REGEN signal from the twl4030 unless 1V8 is =
also
stable, I'd suggest as a simple solution:

	 vcc-supply =3D <&vio>;

Alternatively, we could define a dedicated fixed-regulator in =
omap3-gta04.dtsi
for the 3V3 rail. Which is always-on. This would allow to describe that =
e.g. the
itg3200, panel and other chips and sensors are also supplied by this. =
But since
no driver can really make use of it (turn on/off on demand) this is IMHO =
quite
needless.

BR,
Nikolaus