Qualcomm Shared Memory Point 2 Point binding
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The Shared Memory Point to Point (SMP2P) protocol facilitates communication of
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a single 32-bit value between two processors. Each value has a single writer
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(the local side) and a single reader (the remote side). Values are uniquely
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identified in the system by the directed edge (local processor ID to remote
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processor ID) and a string identifier.
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- compatible:
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Usage: required
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Value type: <string>
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Definition: must be one of:
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"qcom,smp2p"
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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: one entry specifying the smp2p notification interrupt
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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 end of the smp2p edge:
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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,smem:
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Usage: required
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Value type: <u32 array>
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Definition: two identifiers of the inbound and outbound smem items used
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for this edge
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- qcom,local-pid:
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Usage: required
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Value type: <u32>
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Definition: specifies the identfier of the local endpoint of this edge
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- qcom,remote-pid:
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Usage: required
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Value type: <u32>
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Definition: specifies the identfier of the remote endpoint of this edge
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= SUBNODES
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Each SMP2P pair contain a set of inbound and outbound entries, these are
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described in subnodes of the smp2p device node. The node names are not
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important.
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- qcom,entry-name:
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Usage: required
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Value type: <string>
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Definition: specifies the name of this entry, for inbound entries this
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will be used to match against the remotely allocated entry
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and for outbound entries this name is used for allocating
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entries
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- interrupt-controller:
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Usage: required for incoming entries
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Value type: <empty>
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Definition: marks the entry as inbound; the node should be specified
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as a two cell interrupt-controller as defined in
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"../interrupt-controller/interrupts.txt"
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If not specified this node will denote the outgoing entry
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- #interrupt-cells:
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Usage: required for incoming entries
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Value type: <u32>
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Definition: must be 2 - denoting the bit in the entry and IRQ flags
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- #qcom,smem-state-cells:
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Usage: required for outgoing entries
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Value type: <u32>
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Definition: must be 1 - denoting the bit in the entry
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= EXAMPLE
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The following example shows the SMP2P setup with the wireless processor,
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defined from the 8974 apps processor's point-of-view. It encompasses one
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inbound and one outbound entry:
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wcnss-smp2p {
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compatible = "qcom,smp2p";
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qcom,smem = <431>, <451>;
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interrupts = <0 143 1>;
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qcom,ipc = <&apcs 8 18>;
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qcom,local-pid = <0>;
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qcom,remote-pid = <4>;
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wcnss_smp2p_out: master-kernel {
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qcom,entry-name = "master-kernel";
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#qcom,smem-state-cells = <1>;
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};
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wcnss_smp2p_in: slave-kernel {
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qcom,entry-name = "slave-kernel";
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interrupt-controller;
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#interrupt-cells = <2>;
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};
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};
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