On Thu, Jan 12, 2017 at 04:35:43PM -0600, christopher.lee.bostic@xxxxxxxxx wrote:
> 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"
Generally, we don't have a vendor prefix for GPIO based implementations.
> +
> +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"
This and GPIO binding should be in 2 docs.
> +
> +
> +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.
Combine these descriptions and the property names, grouped as below.
> +
> +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";
>From the description, these should be mutually exclusive.
> + 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
>
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