dt-binding: gpio: Introduce qcom,smp2p binding documentation

Introduce binding documentation for the Qualcomm Shared Memory Point 2 Point
protocol implemented as gpio and interrupt controllers.

Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>

diff --git a/Documentation/devicetree/bindings/gpio/qcom,smp2p.txt b/Documentation/devicetree/bindings/gpio/qcom,smp2p.txt
new file mode 100644 (file)
index 0000000..e758c8b
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/qcom,smp2p.txt
@@ -0,0 +1,105 @@
+Qualcomm Shared Memory Point 2 Point binding
+
+The Shared Memory Point to Point (SMP2P) protocol facilitates communication of
+a single 32-bit value between two processors.  Each value has a single writer
+(the local side) and a single reader (the remote side).  Values are uniquely
+identified in the system by the directed edge (local processor ID to remote
+processor ID) and a string identifier. This documents defines the binding for a
+driver that implements and exposes this protocol as a set of GPIO and interrupt
+controllers.
+
+- compatible:
+       Usage: required
+       Value type: <string>
+       Definition: must be one of:
+                   "qcom,smp2p"
+
+- interrupts:
+       Usage: required
+       Value type: <prop-encoded-array>
+       Definition: one entry specifying the smp2p notification interrupt
+
+- qcom,ipc:
+       Usage: required
+       Value type: <prop-encoded-array>
+       Definition: three entries specifying the outgoing ipc bit used for
+                   signaling the remote end of the smp2p edge:
+                   - phandle to a syscon node representing the apcs registers
+                   - u32 representing offset to the register within the syscon
+                   - u32 representing the ipc bit within the register
+
+- qcom,smem:
+       Usage: required
+       Value type: <u32 array>
+       Definition: two identifiers of the inbound and outbound smem items used
+                   for this edge
+
+- qcom,local-pid:
+       Usage: required
+       Value type: <u32>
+       Definition: specifies the identfier of the local endpoint of this edge
+
+- qcom,remote-pid:
+       Usage: required
+       Value type: <u32>
+       Definition: specifies the identfier of the remote endpoint of this edge
+
+= SUBNODES
+Each SMP2P pair contain a set of inbound and outbound entries, these are
+described in subnodes of the smp2p device node. The node names are not
+important.
+
+- qcom,entry-name:
+       Usage: required
+       Value type: <string>
+       Definition: specifies the name of this entry, for inbound entries this
+                   will be used to match against the remotely allocated entry
+                   and for outbound entries this name is used for allocating
+                   entries
+
+- qcom,inbound:
+       Usage: optional
+       Value type: <empty>
+       Definition: marks the entry as inbound; the node should be specified
+                   as a two cell interrupt-controller as defined in 
+                   "../interrupt-controller/interrupts.txt"
+
+- qcom,outbound:
+       Usage: optional
+       Value type: <empty>
+       Definition: marks the entry as outbound; the node should be specified
+                   as a two cell gpio-controller as defined in "gpio.txt"
+
+
+= EXAMPLE
+The following example shows the SMP2P setup with the wireless processor,
+defined from the 8974 apps processor's point-of-view. It encompasses one
+inbound and one outbound entry:
+
+wcnss-smp2p {
+       compatible = "qcom,smp2p";
+       qcom,smem = <431>, <451>;
+
+       interrupts = <0 143 1>;
+
+       qcom,ipc = <&apcs 8 18>;
+
+       qcom,local-pid = <0>;
+       qcom,remote-pid = <4>;
+
+       wcnss_smp2p_out: master-kernel {
+               qcom,entry-name = "master-kernel";
+               qcom,outbound;
+
+               gpio-controller;
+               #gpio-cells = <2>;
+       };
+
+       wcnss_smp2p_in: slave-kernel {
+               qcom,entry-name = "slave-kernel";
+               qcom,inbound;
+
+               interrupt-controller;
+               #interrupt-cells = <2>;
+       };
+};