[RFC 2/7] soc: qcom: Add device tree binding for SMD

[Bjorn Andersson]

Add device tree binding documentation for the Qualcomm Shared Memory
Device.

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

I was looking at having one smd node per remote processor - e.g flatten the
first and second level. As all the channels, for all the remote processors are
allocated from the same pool this does however not feel very natural.

 .../devicetree/bindings/soc/qcom/qcom,smd.txt      |   82 ++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/soc/qcom/qcom,smd.txt

diff --git a/Documentation/devicetree/bindings/soc/qcom/qcom,smd.txt b/Documentation/devicetree/bindings/soc/qcom/qcom,smd.txt
new file mode 100644
index 0000000..c56e4fc
--- /dev/null
+++ b/Documentation/devicetree/bindings/soc/qcom/qcom,smd.txt
@@ -0,0 +1,82 @@
+Qualcomm Shared Memory Driver (SMD) binding
+
+This binding describes the Qualcomm Shared Memory Driver, a fifo based
+communication channel for sending data between the various subsystems in
+Qualcomm platforms.
+
+- compatible:
+	Usage: required
+	Value type: <stringlist>
+	Definition: must be "qcom,smd"
+
+- qcom,smem:
+	Usage: required
+	Value type: <prop-encoded-array>
+	Definition: reference to a smem node managing the shared memory items
+		    used for smd
+
+= EDGES
+
+Each subnode of the SMD node represents a remote subsystem, i.e. a remote
+processor of some sort - in SMD language called an "edge". The name of the
+edges are not important.
+
+- interrupts:
+	Usage: required
+	Value type: <prop-encoded-array>
+	Definition: should specify the IRQ used by the remote processor to
+		    signal this processor about communication related updates
+
+- qcom,ipc:
+	Usage: required
+	Value type: <prop-encoded-array>
+	Definition: three entries specifying the outgoing ipc bit used for
+		    signaling the remote processor:
+		    - 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,smd-edge:
+	Usage: required
+	Value type: <u32>
+	Definition: an identifier representing the remote processor
+
+= SMD DEVICES
+
+In turn, subnodes of the "edges" represent devices tied to SMD channels on that
+"edge". The names of the devices are not important. The properties of these
+nodes are defined by the individual bindings for the SMD devices - but must
+contain the following property:
+
+- qcom,smd-channels:
+	Usage: required
+	Value type: <stringlist>
+	Definition: a list of channels tied to this device, used for matching
+		    the device to channels
+
+= EXAMPLE
+
+The following example represents a smd node, with one edge representing the
+"rpm" subsystem. For the "rpm" subsystem we have a device tied to the
+"rpm_request" channel.
+
+        smd {
+                compatible = "qcom,smd";
+                qcom,smem = <&smem>;
+
+                rpm {
+                        interrupts = <0 168 1>;
+                        qcom,ipc = <&apcs 8 0>;
+                        qcom,smd-edge = <15>;
+
+                        rpm_requests {
+                                compatible = "qcom,rpm-msm8974";
+                                qcom,smd-channels = "rpm_requests";
+
+                                #address-cells = <1>;
+                                #size-cells = <0>;
+
+				...
+			};
+		};
+	};
-- 
1.7.9.5

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