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Date: Thu, 12 Jan 2017 16:35:43 -0600
From: christopher.lee.bostic@...il.com
To: robh+dt@...nel.org, mark.rutland@....com, linux@...linux.org.uk,
gregkh@...uxfoundation.org, mturquette@...libre.com,
geert+renesas@...der.be, devicetree@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, joel@....id.au,
jk@...abs.org, linux-kernel@...r.kernel.org, andrew@...id.au,
alistair@...ple.id.au, benh@...nel.crashing.org
Cc: Chris Bostic <cbostic@...ibm.com>
Subject: [PATCH v2 15/18] drivers/fsi: Add documentation for GPIO based FSI master
From: Chris Bostic <cbostic@...ibm.com>
Define the device tree bindings for the GPIO master type.
Signed-off-by: Chris Bostic <cbostic@...ibm.com>
---
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
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