From: Chris Bostic <cbostic@xxxxxxxxxx> Define the device tree bindings for the GPIO master type. Signed-off-by: Chris Bostic <cbostic@xxxxxxxxxx> --- V2 - Break out this documentation update from the code implementing The GPIO master function. - Move the documentation to an earlier patch than the code implementing the function. - Document all 'compatible' strings used in the series. - Write binding document in terms of hardware, not software. - Elaborate on what a GPIO based FSI master is versus a non GPIO based master. - Give a more detailed description of what each pin in the GPIO FSI master is to be used for. - Re-order compatible strings in example so that most specific comes first. - Indicate the proper order each pin should be initialized. - Fix an unmatched '>' bracket in the example for binding. - Bracket each element of the example list items individually. --- .../devicetree/bindings/fsi/fsi-master-gpio.txt | 71 ++++++++++++++++++++++ 1 file changed, 71 insertions(+) create mode 100644 Documentation/devicetree/bindings/fsi/fsi-master-gpio.txt diff --git a/Documentation/devicetree/bindings/fsi/fsi-master-gpio.txt b/Documentation/devicetree/bindings/fsi/fsi-master-gpio.txt new file mode 100644 index 0000000..5d589bf --- /dev/null +++ b/Documentation/devicetree/bindings/fsi/fsi-master-gpio.txt @@ -0,0 +1,71 @@ +Device-tree bindings for FSI master implemented with GPIO +--------------------------------------------------------- + +Typically a FSI master is defined in hardware with output control +lines designated for Enable, Data, Clock, etc.. In the case of +a 'GPIO FSI master', however, it may be the case that there is no +such master defined in hardware and must be implemented in standard +GPIO to interact with its slaves. In this 'virtual' FSI master +case the GPIO pins representing clk and data are directly +connected to the slaves. + +The GPIO FSI master node +------------------------- +This node describes a FSI master implmented with GPIO. +Required property: + compatible = "ibm,fsi-master-gpio" + +The standard FSI master node +---------------------------- +This node describes a FSI master implmemented fully in hardware +with dedicated input/output pins required for its function (i.e. +not using generic GPIO pins). +Required property: + compatible = "ibm,fsi-master" + + +GPIO FSI master property/pin descriptions +------------------------------------------ +clk - The master controlled clock line that indicates to the + slave when to read in or send out new data - required. +data - The serial data line containing information to be sent or + received by the master. This line is bi-directional. During + command phase the master controls the line and when a response + is required the slave takes control - required. +enable - Controls power state of data line - optional. +trans - Voltage translator control. In some applications the data line + must have its signal levels altered by a translator. If this is + necessary then control of signal direction is managed via this + line - optional. +mux - Multiplexor control. This activates/deactivates the data line + in cases where it is one of many possible selections via mux - + optional. + +Required properties: + - compatible = "ibm,fsi-master-gpio"; + - clk-gpios; + - data-gpios; + +Optional properties: + - enable-gpios; + - trans-gpios; + - mux-gpios; + +Order of property activation: +1. clk +2. data +3. trans +4. enable +5. mux + + +Example: + +fsi-master { + compatible = "ibm,fsi-master-gpio", "ibm,fsi-master"; + clk-gpios = <&gpio 0>, <&gpio 6>; + data-gpios = <&gpio 1>, <&gpio 7>; + enable-gpios = <&gpio 2>, <&gpio 8>; + trans-gpios = <&gpio 3>, <&gpio 9>; + mux-gpios = <&gpio 4>, <&gpio 10>; +} -- 1.8.2.2 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html