[PATCH 3/4] bus: Add DT bindings for 96Boards low speed connector
From: robh+dt@kernel.org (Rob Herring)
Date: 2018-08-23 13:45:52
Also in:
linux-devicetree
On Thu, Aug 23, 2018 at 5:33 AM Linus Walleij [off-list ref] wrote:
We need to be able to grab resources on a 96Boards low speed connector to populate and use a daughterboard, so define some very rudimentary properties simply passing phandles for the resources used on the low speed connector.
This only works for describing what's on the connector, but does nothing for describing downstream devices on the connector. We already have a way to do the former with label properties at least for uart, i2c and spi. And gpio has it's own method of labeling lines.
quoted hunk ↗ jump to hunk
Signed-off-by: Linus Walleij <redacted> --- .../bus/96boards,low-speed-connector.txt | 50 +++++++++++++++++++ 1 file changed, 50 insertions(+) create mode 100644 Documentation/devicetree/bindings/bus/96boards,low-speed-connector.txtdiff --git a/Documentation/devicetree/bindings/bus/96boards,low-speed-connector.txt b/Documentation/devicetree/bindings/bus/96boards,low-speed-connector.txt new file mode 100644 index 000000000000..6631b3edd01f --- /dev/null +++ b/Documentation/devicetree/bindings/bus/96boards,low-speed-connector.txt@@ -0,0 +1,50 @@ +96Boards Low Speed Connectors + +The 96Boards connectors represent a non-dicoverable Low Speed (LS) +and High Speed (HS) external bus on the 96Board development +boards. Each 96Board presents both of these connectors. + +The Low Speed (LS) connector is a 40 pin 2x20 female pin header: +- Power +- Two buttons: power and reset +- 2 x UART one optional with just RX/TX, one required with modem + CTS/RTS +- 2 x I2C +- 1 x SPI +- 1 x I2S (audio) +- 12 x GPIO lines named GPIO-A thru GPIO-L + +Further details on the electronics and signals are available in +"96Boards Consumer Edition, Low Cost Hardware Platform Specification" +As of writing version 1.0, January 2015. + +Required properties: + +- compatible: shall be "96boards,low-speed-connector" +- i2c0: phandle to the I2C0 bus +- i2c1: phandle to the I2C1 bus +- spi: phandle to the SPI bus +- gpios: a list of phandles to the GPIOs connected to the + connector. The handles need to be uniformly specified with the + 0 flag as the connector is not the end consumer. + +Example: + +lscon: connector { + compatible = "96boards,low-speed-connector"; + i2c0 = <&i2csw_0>; + i2c1 = <&i2csw_1>; + spi = <&spi0>;
David G has suggested using aliases (in this node, not top-level) for this purpose of mapping things like spi and i2c, and I think that's a good use of aliases (versus spi and i2c aliases at the top level which I don't). The hard part is still how to structure the child devices.
+ gpios = <&gpio 36 0>, /* GPIO-A */
We defined 'gpio-map' specifically for handling GPIOs thru connectors.
It's in the DT spec (though not a released version yet). Use it here.
Sorry, but the only halfway solution I'm going to accept is one which
can evolve into a full solution. Define the basic structure and add
each interface one by one. Maybe that starts with just:
lscon: connector {
compatible = "96boards,low-speed-connector";
};
That's not really my recommendation as that's really just kicking the
can down the road.
Rob