1 System Control and Power Interface (SCPI) Message Protocol
2 ----------------------------------------------------------
4 Firmware implementing the SCPI described in ARM document number ARM DUI 0922B
5 ("ARM Compute Subsystem SCP: Message Interface Protocols")[0] can be used
6 by Linux to initiate various system control and power operations.
10 - compatible : should be
11 * "arm,scpi" : For implementations complying to SCPI v1.0 or above
12 * "arm,scpi-pre-1.0" : For implementations complying to all
13 unversioned releases prior to SCPI v1.0
14 - mboxes: List of phandle and mailbox channel specifiers
15 All the channels reserved by remote SCP firmware for use by
16 SCPI message protocol should be specified in any order
17 - shmem : List of phandle pointing to the shared memory(SHM) area between the
18 processors using these mailboxes for IPC, one for each mailbox
19 SHM can be any memory reserved for the purpose of this communication
20 between the processors.
22 See Documentation/devicetree/bindings/mailbox/mailbox.txt
23 for more details about the generic mailbox controller and
24 client driver bindings.
26 Clock bindings for the clocks based on SCPI Message Protocol
27 ------------------------------------------------------------
29 This binding uses the common clock binding[1].
34 - compatible : should be "arm,scpi-clocks"
35 All the clocks provided by SCP firmware via SCPI message
36 protocol much be listed as sub-nodes under this node.
41 - compatible : shall include one of the following
42 "arm,scpi-dvfs-clocks" - all the clocks that are variable and index based.
43 These clocks don't provide an entire range of values between the
44 limits but only discrete points within the range. The firmware
45 provides the mapping for each such operating frequency and the
46 index associated with it. The firmware also manages the
47 voltage scaling appropriately with the clock scaling.
48 "arm,scpi-variable-clocks" - all the clocks that are variable and provide full
49 range within the specified range. The firmware provides the
50 range of values within a specified range.
52 Other required properties for all clocks(all from common clock binding):
53 - #clock-cells : Should be 1. Contains the Clock ID value used by SCPI commands.
54 - clock-output-names : shall be the corresponding names of the outputs.
55 - clock-indices: The identifying number for the clocks(i.e.clock_id) in the
56 node. It can be non linear and hence provide the mapping of identifiers
57 into the clock-output-names array.
59 Sensor bindings for the sensors based on SCPI Message Protocol
60 --------------------------------------------------------------
61 SCPI provides an API to access the various sensors on the SoC.
64 - compatible : should be "arm,scpi-sensors".
65 - #thermal-sensor-cells: should be set to 1. This property follows the
66 thermal device tree bindings[2].
68 Valid cell values are raw identifiers (Sensor ID)
69 as used by the firmware. Refer to platform details
70 for your implementation for the IDs to use.
72 Power domain bindings for the power domains based on SCPI Message Protocol
73 ------------------------------------------------------------
75 This binding uses the generic power domain binding[4].
81 - #power-domain-cells : Should be 1. Contains the device or the power
82 domain ID value used by SCPI commands.
83 - num-domains: Total number of power domains provided by SCPI. This is
84 needed as the SCPI message protocol lacks a mechanism to
85 query this information at runtime.
91 - power-domains : A phandle and PM domain specifier as defined by bindings of
92 the power controller specified by phandle.
94 [0] http://infocenter.arm.com/help/topic/com.arm.doc.dui0922b/index.html
95 [1] Documentation/devicetree/bindings/clock/clock-bindings.txt
96 [2] Documentation/devicetree/bindings/thermal/thermal*.yaml
97 [3] Documentation/devicetree/bindings/sram/sram.yaml
98 [4] Documentation/devicetree/bindings/power/power-domain.yaml
102 sram: sram@50000000 {
103 compatible = "arm,juno-sram-ns", "mmio-sram";
104 reg = <0x0 0x50000000 0x0 0x10000>;
106 #address-cells = <1>;
108 ranges = <0 0x0 0x50000000 0x10000>;
110 cpu_scp_lpri: scp-shmem@0 {
111 compatible = "arm,juno-scp-shmem";
115 cpu_scp_hpri: scp-shmem@200 {
116 compatible = "arm,juno-scp-shmem";
121 mailbox: mailbox0@40000000 {
126 scpi_protocol: scpi@2e000000 {
127 compatible = "arm,scpi";
128 mboxes = <&mailbox 0 &mailbox 1>;
129 shmem = <&cpu_scp_lpri &cpu_scp_hpri>;
132 compatible = "arm,scpi-clocks";
134 scpi_dvfs: scpi_clocks@0 {
135 compatible = "arm,scpi-dvfs-clocks";
137 clock-indices = <0>, <1>, <2>;
138 clock-output-names = "atlclk", "aplclk","gpuclk";
140 scpi_clk: scpi_clocks@3 {
141 compatible = "arm,scpi-variable-clocks";
143 clock-indices = <3>, <4>;
144 clock-output-names = "pxlclk0", "pxlclk1";
148 scpi_sensors0: sensors {
149 compatible = "arm,scpi-sensors";
150 #thermal-sensor-cells = <1>;
153 scpi_devpd: scpi-power-domains {
154 compatible = "arm,scpi-power-domains";
156 #power-domain-cells = <1>;
163 clocks = <&scpi_dvfs 0>;
168 reg = <0 0x7ff60000 0 0x1000>;
169 clocks = <&scpi_clk 4>;
170 power-domains = <&scpi_devpd 1>;
175 polling-delay-passive = <100>;
176 polling-delay = <1000>;
179 thermal-sensors = <&scpi_sensors0 3>;
184 In the above example, the #clock-cells is set to 1 as required.
185 scpi_dvfs has 3 output clocks namely: atlclk, aplclk, and gpuclk with 0,
186 1 and 2 as clock-indices. scpi_clk has 2 output clocks namely: pxlclk0
187 and pxlclk1 with 3 and 4 as clock-indices.
189 The first consumer in the example is cpu@0 and it has '0' as the clock
190 specifier which points to the first entry in the output clocks of
191 scpi_dvfs i.e. "atlclk".
193 Similarly the second example is hdlcd@7ff60000 and it has pxlclk1 as input
194 clock. '4' in the clock specifier here points to the second entry
195 in the output clocks of scpi_clocks i.e. "pxlclk1"
197 The thermal-sensors property in the soc_thermal node uses the
198 temperature sensor provided by SCP firmware to setup a thermal
199 zone. The ID "3" is the sensor identifier for the temperature sensor
200 as used by the firmware.
202 The num-domains property in scpi-power-domains domain specifies that
203 SCPI provides 2 power domains. The hdlcd node uses the power domain with