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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"
= EDGES
Each subnode of the SMD node represents a remote subsystem or a remote
processor of some sort - or in SMD language an "edge". The name of the edges
are not important.
The edge is described by the following properties:
- 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
- mboxes:
Usage: required
Value type: <prop-encoded-array>
Definition: reference to the associated doorbell in APCS, as described
in mailbox/mailbox.txt
- qcom,ipc:
Usage: required, unless mboxes is specified
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: the identifier of the remote processor in the smd channel
allocation table
- qcom,remote-pid:
Usage: optional
Value type: <u32>
Definition: the identifier for the remote processor as known by the rest
of the system.
- label:
Usage: optional
Value type: <string>
Definition: name of the edge, used for debugging and identification
purposes. The node name will be used if this is not
present.
= 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.
apcs: syscon@f9011000 {
compatible = "syscon";
reg = <0xf9011000 0x1000>;
};
smd {
compatible = "qcom,smd";
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";
...
};
};
};
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