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

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Date:   Mon, 28 Jan 2019 16:46:53 +0100
From:   Loys Ollivier <lollivier@...libre.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     Loys Ollivier <lollivier@...libre.com>, 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 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.
>> 
>>  .../devicetree/bindings/gnss/mediatek.txt          | 39 
>>  ++++++++++++++++++++++
>>  1 file changed, 39 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..fd984b4a9a6d
>> --- /dev/null
>> +++ 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.

>> +
>> +- vcc-supply	: Main voltage regulator (pin name: 3V3_IN, VCC, VDD)
>
> The pin names in parenthesis were copied from the sirf-star binding and
> were used to capture the various names given to this supply by different
> vendors. Please drop as it doesn't apply here.
>
>> +
>> +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.
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.

>> +Optional properties:
>> +
>> +- timepulse-gpios	: Time pulse GPIO
>> +- v-bckp-supply		: Backup voltage regulator
>> +- current-speed		: Default UART baud rate
>
> Looks like you forgot the optional NRESET input and 3D-FIX output (even
> if the latter might be of limited use).
>

Thanks I will clean this section.

>> +
>> +Example:
>> +
>> +serial@...4 {
>> +	compatible = "ns16550a";
>> +
>> +	gnss {
>> +		compatible = "globaltop,pa6h";
>> +		vcc-supply = <&vcc_3v3>;
>> +	};
>> +};
>
> Johan


-- 
-L