linux-kernel - Re: [PATCH v2 2/4] dt-bindings: gnss: add mediatek binding

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Date:   Mon, 11 Feb 2019 09:33:49 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Loys Ollivier <lollivier@...libre.com>
Cc:     Johan Hovold <johan@...nel.org>, devicetree@...r.kernel.org,
        Rob Herring <robh+dt@...nel.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 v2 2/4] dt-bindings: gnss: add mediatek binding

On Mon, Jan 28, 2019 at 04:46:53PM +0100, Loys Ollivier wrote:
> 
> On Fri 25 Jan 2019 at 09:07, Johan Hovold wrote:
> 
> > On Thu, Jan 17, 2019 at 05:54:32PM +0100, Loys Ollivier wrote:
> >> Add binding for Mediatek-based GNSS receivers.
> >> 
> >> Signed-off-by: Loys Ollivier <lollivier@...libre.com>
> >> ---
> >> 
> >> 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.

> >> +++ b/Documentation/devicetree/bindings/gnss/mediatek.txt
> >> @@ -0,0 +1,39 @@
> >> +Mediatek-based GNSS Receiver DT binding
> >> +
> >> +Mediatek chipsets are used in GNSS-receiver modules produced by several
> >> +vendors and can use UART, SPI or I2C interfaces.
> >> +
> >> +Please see Documentation/devicetree/bindings/gnss/gnss.txt for generic
> >> +properties.
> >> +
> >> +Required properties:
> >> +
> >> +- compatible	: Must be one of
> >> +
> >> +			"globaltop,pa6h"
> >> +			"mediatek,mt3339"
> >
> > I'm not sure it makes sense to add the GPS chip itself as it cannot be
> > used stand-alone AFAIU, and either not way would require a lot more
> > resources to be defined than what you add to this binding.
> 
> OK, I find it a bit confusing to have Mediatek bindings but no
> compatible Mediatek SoCs.
> But it is true that it can't be used stand-alone. I will remove this
> reference and also remove it from the mtk.c driver code from this patch
> serie.

> >> +Required properties (I2C):
> >> +- reg		: I2C slave address
> >> +
> >> +Required properties (SPI):
> >> +- reg		: SPI chip select address
> >
> > While the mt3339 appears to support these interfaces, the globaltop one
> > does not.
> >
> > Have you looked around for a small sample of mt3339-based receivers, to
> > see whether anyone actually provides these?
> 
> Again I'm confused by the fact that it is the Mediatek bindings.
> Hence why I have added it and why it was not present in the v1 that was
> only for Globaltop.

This is no different from the sirfstar driver for receivers based on
those chipsets but manufactured by various other vendors.

> I find it odd mentionning the chipset but not all its interfaces.
> I will remove these sections and only list supported interfaces (i.e.
> UART). Other interfaces can be added afterward if one finds a board that
> provides them.

Right, but please do look around for other receivers using this chipset
so that we can make the binding generic enough to cover those as well
(e.g. by choosing representative resource names).

Johan