Documentation/devicetree/bindings/soc/qcom/qcom,smd.txt

   1 Qualcomm Shared Memory Driver (SMD) binding
   2
   3 This binding describes the Qualcomm Shared Memory Driver, a fifo based
   4 communication channel for sending data between the various subsystems in
   5 Qualcomm platforms.
   6
   7 - compatible:
   8         Usage: required
   9         Value type: <stringlist>
  10         Definition: must be "qcom,smd"
  11
  12 = EDGES
  13
  14 Each subnode of the SMD node represents a remote subsystem or a remote
  15 processor of some sort - or in SMD language an "edge". The name of the edges
  16 are not important.
  17 The edge is described by the following properties:
  18
  19 - interrupts:
  20         Usage: required
  21         Value type: <prop-encoded-array>
  22         Definition: should specify the IRQ used by the remote processor to
  23                     signal this processor about communication related updates
  24
  25 - qcom,ipc:
  26         Usage: required
  27         Value type: <prop-encoded-array>
  28         Definition: three entries specifying the outgoing ipc bit used for
  29                     signaling the remote processor:
  30                     - phandle to a syscon node representing the apcs registers
  31                     - u32 representing offset to the register within the syscon
  32                     - u32 representing the ipc bit within the register
  33
  34 - qcom,smd-edge:
  35         Usage: required
  36         Value type: <u32>
  37         Definition: the identifier of the remote processor in the smd channel
  38                     allocation table
  39
  40 - qcom,remote-pid:
  41         Usage: optional
  42         Value type: <u32>
  43         Definition: the identifier for the remote processor as known by the rest
  44                     of the system.
  45
  46 = SMD DEVICES
  47
  48 In turn, subnodes of the "edges" represent devices tied to SMD channels on that
  49 "edge". The names of the devices are not important. The properties of these
  50 nodes are defined by the individual bindings for the SMD devices - but must
  51 contain the following property:
  52
  53 - qcom,smd-channels:
  54         Usage: required
  55         Value type: <stringlist>
  56         Definition: a list of channels tied to this device, used for matching
  57                     the device to channels
  58
  59 = EXAMPLE
  60
  61 The following example represents a smd node, with one edge representing the
  62 "rpm" subsystem. For the "rpm" subsystem we have a device tied to the
  63 "rpm_request" channel.
  64
  65         apcs: syscon@f9011000 {
  66                 compatible = "syscon";
  67                 reg = <0xf9011000 0x1000>;
  68         };
  69
  70         smd {
  71                 compatible = "qcom,smd";
  72
  73                 rpm {
  74                         interrupts = <0 168 1>;
  75                         qcom,ipc = <&apcs 8 0>;
  76                         qcom,smd-edge = <15>;
  77
  78                         rpm_requests {
  79                                 compatible = "qcom,rpm-msm8974";
  80                                 qcom,smd-channels = "rpm_requests";
  81
  82                                 ...
  83                         };
  84                 };
  85         };