[PATCH v3 16/18] drivers/fsi: Add documentation for GPIO based FSI master
From: robh@kernel.org (Rob Herring)
Date: 2017-02-07 17:27:52
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linux-devicetree, lkml
On Wed, Feb 01, 2017 at 10:53:56AM -0600, Christopher Bostic wrote:
quoted hunk ↗ jump to hunk
From: Chris Bostic <redacted> Define the device tree bindings for the GPIO master type. Signed-off-by: Chris Bostic <redacted> --- .../devicetree/bindings/fsi/fsi-master-gpio.txt | 71 ++++++++++++++++++++++ 1 file changed, 71 insertions(+) create mode 100644 Documentation/devicetree/bindings/fsi/fsi-master-gpio.txtdiff --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"
This section still needs to be a separate doc. And ibm,fsi-master is too generic.
+ + +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.
Just put the definitions with the properties (i.e. clk-gpios).
+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";Aren't these 2 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