Documentation/devicetree/bindings/arm/arm,scmi.txt

   1 System Control and Management Interface (SCMI) Message Protocol
   2 ----------------------------------------------------------
   3
   4 The SCMI is intended to allow agents such as OSPM to manage various functions
   5 that are provided by the hardware platform it is running on, including power
   6 and performance functions.
   7
   8 This binding is intended to define the interface the firmware implementing
   9 the SCMI as described in ARM document number ARM DEN 0056A ("ARM System Control
  10 and Management Interface Platform Design Document")[0] provide for OSPM in
  11 the device tree.
  12
  13 Required properties:
  14
  15 The scmi node with the following properties shall be under the /firmware/ node.
  16
  17 - compatible : shall be "arm,scmi" or "arm,scmi-smc" for smc/hvc transports
  18 - mboxes: List of phandle and mailbox channel specifiers. It should contain
  19           exactly one or two mailboxes, one for transmitting messages("tx")
  20           and another optional for receiving the notifications("rx") if
  21           supported.
  22 - shmem : List of phandle pointing to the shared memory(SHM) area as per
  23           generic mailbox client binding.
  24 - #address-cells : should be '1' if the device has sub-nodes, maps to
  25           protocol identifier for a given sub-node.
  26 - #size-cells : should be '0' as 'reg' property doesn't have any size
  27           associated with it.
  28 - arm,smc-id : SMC id required when using smc or hvc transports
  29
  30 Optional properties:
  31
  32 - mbox-names: shall be "tx" or "rx" depending on mboxes entries.
  33
  34 - interrupts : when using smc or hvc transports, this optional
  35          property indicates that msg completion by the platform is indicated
  36          by an interrupt rather than by the return of the smc call. This
  37          should not be used except when the platform requires such behavior.
  38
  39 - interrupt-names : if "interrupts" is present, interrupt-names must also
  40          be present and have the value "a2p".
  41
  42 See Documentation/devicetree/bindings/mailbox/mailbox.txt for more details
  43 about the generic mailbox controller and client driver bindings.
  44
  45 The mailbox is the only permitted method of calling the SCMI firmware.
  46 Mailbox doorbell is used as a mechanism to alert the presence of a
  47 messages and/or notification.
  48
  49 Each protocol supported shall have a sub-node with corresponding compatible
  50 as described in the following sections. If the platform supports dedicated
  51 communication channel for a particular protocol, the 3 properties namely:
  52 mboxes, mbox-names and shmem shall be present in the sub-node corresponding
  53 to that protocol.
  54
  55 Clock/Performance bindings for the clocks/OPPs based on SCMI Message Protocol
  56 ------------------------------------------------------------
  57
  58 This binding uses the common clock binding[1].
  59
  60 Required properties:
  61 - #clock-cells : Should be 1. Contains the Clock ID value used by SCMI commands.
  62
  63 Power domain bindings for the power domains based on SCMI Message Protocol
  64 ------------------------------------------------------------
  65
  66 This binding for the SCMI power domain providers uses the generic power
  67 domain binding[2].
  68
  69 Required properties:
  70  - #power-domain-cells : Should be 1. Contains the device or the power
  71                          domain ID value used by SCMI commands.
  72
  73 Regulator bindings for the SCMI Regulator based on SCMI Message Protocol
  74 ------------------------------------------------------------
  75 An SCMI Regulator is permanently bound to a well defined SCMI Voltage Domain,
  76 and should be always positioned as a root regulator.
  77 It does not support any current operation.
  78
  79 SCMI Regulators are grouped under a 'regulators' node which in turn is a child
  80 of the SCMI Voltage protocol node inside the desired SCMI instance node.
  81
  82 This binding uses the common regulator binding[6].
  83
  84 Required properties:
  85  - reg : shall identify an existent SCMI Voltage Domain.
  86
  87 Sensor bindings for the sensors based on SCMI Message Protocol
  88 --------------------------------------------------------------
  89 SCMI provides an API to access the various sensors on the SoC.
  90
  91 Required properties:
  92 - #thermal-sensor-cells: should be set to 1. This property follows the
  93                          thermal device tree bindings[3].
  94
  95                          Valid cell values are raw identifiers (Sensor ID)
  96                          as used by the firmware. Refer to  platform details
  97                          for your implementation for the IDs to use.
  98
  99 Reset signal bindings for the reset domains based on SCMI Message Protocol
 100 ------------------------------------------------------------
 101
 102 This binding for the SCMI reset domain providers uses the generic reset
 103 signal binding[5].
 104
 105 Required properties:
 106  - #reset-cells : Should be 1. Contains the reset domain ID value used
 107                   by SCMI commands.
 108
 109 SRAM and Shared Memory for SCMI
 110 -------------------------------
 111
 112 A small area of SRAM is reserved for SCMI communication between application
 113 processors and SCP.
 114
 115 The properties should follow the generic mmio-sram description found in [4]
 116
 117 Each sub-node represents the reserved area for SCMI.
 118
 119 Required sub-node properties:
 120 - reg : The base offset and size of the reserved area with the SRAM
 121 - compatible : should be "arm,scmi-shmem" for Non-secure SRAM based
 122                shared memory
 123
 124 [0] http://infocenter.arm.com/help/topic/com.arm.doc.den0056a/index.html
 125 [1] Documentation/devicetree/bindings/clock/clock-bindings.txt
 126 [2] Documentation/devicetree/bindings/power/power-domain.yaml
 127 [3] Documentation/devicetree/bindings/thermal/thermal*.yaml
 128 [4] Documentation/devicetree/bindings/sram/sram.yaml
 129 [5] Documentation/devicetree/bindings/reset/reset.txt
 130 [6] Documentation/devicetree/bindings/regulator/regulator.yaml
 131
 132 Example:
 133
 134 sram@50000000 {
 135         compatible = "mmio-sram";
 136         reg = <0x0 0x50000000 0x0 0x10000>;
 137
 138         #address-cells = <1>;
 139         #size-cells = <1>;
 140         ranges = <0 0x0 0x50000000 0x10000>;
 141
 142         cpu_scp_lpri: scp-shmem@0 {
 143                 compatible = "arm,scmi-shmem";
 144                 reg = <0x0 0x200>;
 145         };
 146
 147         cpu_scp_hpri: scp-shmem@200 {
 148                 compatible = "arm,scmi-shmem";
 149                 reg = <0x200 0x200>;
 150         };
 151 };
 152
 153 mailbox@40000000 {
 154         ....
 155         #mbox-cells = <1>;
 156         reg = <0x0 0x40000000 0x0 0x10000>;
 157 };
 158
 159 firmware {
 160
 161         ...
 162
 163         scmi {
 164                 compatible = "arm,scmi";
 165                 mboxes = <&mailbox 0 &mailbox 1>;
 166                 mbox-names = "tx", "rx";
 167                 shmem = <&cpu_scp_lpri &cpu_scp_hpri>;
 168                 #address-cells = <1>;
 169                 #size-cells = <0>;
 170
 171                 scmi_devpd: protocol@11 {
 172                         reg = <0x11>;
 173                         #power-domain-cells = <1>;
 174                 };
 175
 176                 scmi_dvfs: protocol@13 {
 177                         reg = <0x13>;
 178                         #clock-cells = <1>;
 179                 };
 180
 181                 scmi_clk: protocol@14 {
 182                         reg = <0x14>;
 183                         #clock-cells = <1>;
 184                 };
 185
 186                 scmi_sensors0: protocol@15 {
 187                         reg = <0x15>;
 188                         #thermal-sensor-cells = <1>;
 189                 };
 190
 191                 scmi_reset: protocol@16 {
 192                         reg = <0x16>;
 193                         #reset-cells = <1>;
 194                 };
 195
 196                 scmi_voltage: protocol@17 {
 197                         reg = <0x17>;
 198
 199                         regulators {
 200                                 regulator_devX: regulator@0 {
 201                                         reg = <0x0>;
 202                                         regulator-max-microvolt = <3300000>;
 203                                 };
 204
 205                                 regulator_devY: regulator@9 {
 206                                         reg = <0x9>;
 207                                         regulator-min-microvolt = <500000>;
 208                                         regulator-max-microvolt = <4200000>;
 209                                 };
 210
 211                                 ...
 212                         };
 213                 };
 214         };
 215 };
 216
 217 cpu@0 {
 218         ...
 219         reg = <0 0>;
 220         clocks = <&scmi_dvfs 0>;
 221 };
 222
 223 hdlcd@7ff60000 {
 224         ...
 225         reg = <0 0x7ff60000 0 0x1000>;
 226         clocks = <&scmi_clk 4>;
 227         power-domains = <&scmi_devpd 1>;
 228         resets = <&scmi_reset 10>;
 229 };
 230
 231 thermal-zones {
 232         soc_thermal {
 233                 polling-delay-passive = <100>;
 234                 polling-delay = <1000>;
 235                                         /* sensor ID */
 236                 thermal-sensors = <&scmi_sensors0 3>;
 237                 ...
 238         };
 239 };