Qualcomm Shared Memory Driver (SMD) binding
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This binding describes the Qualcomm Shared Memory Driver, a fifo based
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communication channel for sending data between the various subsystems in
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Qualcomm platforms.
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- compatible:
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Usage: required
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Value type: <stringlist>
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Definition: must be "qcom,smd"
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= EDGES
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Each subnode of the SMD node represents a remote subsystem or a remote
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processor of some sort - or in SMD language an "edge". The name of the edges
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are not important.
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The edge is described by the following properties:
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- interrupts:
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Usage: required
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Value type: <prop-encoded-array>
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Definition: should specify the IRQ used by the remote processor to
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signal this processor about communication related updates
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- mboxes:
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Usage: required
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Value type: <prop-encoded-array>
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Definition: reference to the associated doorbell in APCS, as described
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in mailbox/mailbox.txt
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- qcom,ipc:
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Usage: required, unless mboxes is specified
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Value type: <prop-encoded-array>
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Definition: three entries specifying the outgoing ipc bit used for
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signaling the remote processor:
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- phandle to a syscon node representing the apcs registers
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- u32 representing offset to the register within the syscon
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- u32 representing the ipc bit within the register
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- qcom,smd-edge:
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Usage: required
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Value type: <u32>
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Definition: the identifier of the remote processor in the smd channel
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allocation table
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- qcom,remote-pid:
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Usage: optional
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Value type: <u32>
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Definition: the identifier for the remote processor as known by the rest
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of the system.
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- label:
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Usage: optional
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Value type: <string>
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Definition: name of the edge, used for debugging and identification
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purposes. The node name will be used if this is not
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present.
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= SMD DEVICES
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In turn, subnodes of the "edges" represent devices tied to SMD channels on that
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"edge". The names of the devices are not important. The properties of these
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nodes are defined by the individual bindings for the SMD devices - but must
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contain the following property:
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- qcom,smd-channels:
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Usage: required
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Value type: <stringlist>
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Definition: a list of channels tied to this device, used for matching
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the device to channels
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= EXAMPLE
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The following example represents a smd node, with one edge representing the
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"rpm" subsystem. For the "rpm" subsystem we have a device tied to the
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"rpm_request" channel.
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apcs: syscon@f9011000 {
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compatible = "syscon";
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reg = <0xf9011000 0x1000>;
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};
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smd {
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compatible = "qcom,smd";
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rpm {
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interrupts = <0 168 1>;
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qcom,ipc = <&apcs 8 0>;
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qcom,smd-edge = <15>;
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rpm_requests {
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compatible = "qcom,rpm-msm8974";
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qcom,smd-channels = "rpm_requests";
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...
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};
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};
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};
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