Re: [PATCH RFC 1/2] Documentation: add Device tree bindings for QCA7000

[Mark Rutland <mark.rutland@arm.com>]

On Mon, Apr 28, 2014 at 06:54:56PM +0100, Stefan Wahren wrote:
> This patch adds the Device tree bindings for the Ethernet over SPI
> protocol driver of the Qualcomm QCA7000 HomePlug GreenPHY.
> 
> Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
> ---
>  .../devicetree/bindings/net/qca-qca7000-spi.txt    |   51 ++++++++++++++++++++
>  1 file changed, 51 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/net/qca-qca7000-spi.txt
> 
> diff --git a/Documentation/devicetree/bindings/net/qca-qca7000-spi.txt b/Documentation/devicetree/bindings/net/qca-qca7000-spi.txt
> new file mode 100644
> index 0000000..132c10f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/net/qca-qca7000-spi.txt
> @@ -0,0 +1,51 @@
> +* Qualcomm QCA7000 (Ethernet over SPI protocol)
> +
> +Note: The QCA7000 is useable as a SPI device. In this case it must be defined
> +as a child of a spi master in the device tree.
> +
> +Required properties:
> +- compatible : Should be "qca,qca7000"
> +- reg : Should specify the SPI chip select
> +- intr-gpios : Should specify the GPIO for SPI interrupt

As Arnd mentioned, this should be described as an interrupt if it's an
interrupt from the point of view of the QCA7000.

> +- spi-cpha : Must be set
> +- spi-cpol: Must be set
> +
> +Optional properties:
> +- spi-max-frequency : Maximum frequency of the SPI bus the chip can operate at.
> +  Numbers smaller than 1000000 or greater than 16000000 are invalid. Missing
> +  the property will set the SPI frequency to 8000000 Hertz.
> +- local-mac-address: 6 bytes, mac address
> +- qca,legacy-mode : Should specify the data transfer mode of the QCA7000
> +  (0 = burst mode, 1 = legacy mode). Missing the property will use the
> +  burst mode.

This sounds like it could be a boolean property (one with no value, like
cpi-cpha). When is this necessary?

> +- linux,burst-length : Number of data bytes per burst. Numbers smaller than 1
> +  or greater than 5000 are invalid. Missing the property will set the
> +  burst length to 5000 bytes. This property has only an effect in burst mode.

When is this needed?

> +- linux,pluggable-connection : Should be set to skip signature check while
> +  probing. This property is useful if the SPI master and QCA7000 are not on the
> +  same board.

This does not sounds like it belongs in the DT, as it's strongly tied to the
implementation of the driver. Why is this necessary?

Cheers,
Mark.