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 "arm,scpi"
11 - mboxes: List of phandle and mailbox channel specifiers
12 All the channels reserved by remote SCP firmware for use by
13 SCPI message protocol should be specified in any order
14 - shmem : List of phandle pointing to the shared memory(SHM) area between the
15 processors using these mailboxes for IPC, one for each mailbox
16 SHM can be any memory reserved for the purpose of this communication
17 between the processors.
19 See Documentation/devicetree/bindings/mailbox/mailbox.txt
20 for more details about the generic mailbox controller and
21 client driver bindings.
23 Clock bindings for the clocks based on SCPI Message Protocol
24 ------------------------------------------------------------
26 This binding uses the common clock binding[1].
31 - compatible : should be "arm,scpi-clocks"
32 All the clocks provided by SCP firmware via SCPI message
33 protocol much be listed as sub-nodes under this node.
38 - compatible : shall include one of the following
39 "arm,scpi-dvfs-clocks" - all the clocks that are variable and index based.
40 These clocks don't provide an entire range of values between the
41 limits but only discrete points within the range. The firmware
42 provides the mapping for each such operating frequency and the
43 index associated with it. The firmware also manages the
44 voltage scaling appropriately with the clock scaling.
45 "arm,scpi-variable-clocks" - all the clocks that are variable and provide full
46 range within the specified range. The firmware provides the
47 range of values within a specified range.
49 Other required properties for all clocks(all from common clock binding):
50 - #clock-cells : Should be 1. Contains the Clock ID value used by SCPI commands.
51 - clock-output-names : shall be the corresponding names of the outputs.
52 - clock-indices: The identifying number for the clocks(i.e.clock_id) in the
53 node. It can be non linear and hence provide the mapping of identifiers
54 into the clock-output-names array.
56 SRAM and Shared Memory for SCPI
57 -------------------------------
59 A small area of SRAM is reserved for SCPI communication between application
63 - compatible : should be "arm,juno-sram-ns" for Non-secure SRAM on Juno
65 The rest of the properties should follow the generic mmio-sram description
66 found in ../../misc/sysram.txt
68 Each sub-node represents the reserved area for SCPI.
70 Required sub-node properties:
71 - reg : The base offset and size of the reserved area with the SRAM
72 - compatible : should be "arm,juno-scp-shmem" for Non-secure SRAM based
73 shared memory on Juno platforms
75 [0] http://infocenter.arm.com/help/topic/com.arm.doc.dui0922b/index.html
76 [1] Documentation/devicetree/bindings/clock/clock-bindings.txt
81 compatible = "arm,juno-sram-ns", "mmio-sram";
82 reg = <0x0 0x50000000 0x0 0x10000>;
86 ranges = <0 0x0 0x50000000 0x10000>;
88 cpu_scp_lpri: scp-shmem@0 {
89 compatible = "arm,juno-scp-shmem";
93 cpu_scp_hpri: scp-shmem@200 {
94 compatible = "arm,juno-scp-shmem";
99 mailbox: mailbox0@40000000 {
104 scpi_protocol: scpi@2e000000 {
105 compatible = "arm,scpi";
106 mboxes = <&mailbox 0 &mailbox 1>;
107 shmem = <&cpu_scp_lpri &cpu_scp_hpri>;
110 compatible = "arm,scpi-clocks";
112 scpi_dvfs: scpi_clocks@0 {
113 compatible = "arm,scpi-dvfs-clocks";
115 clock-indices = <0>, <1>, <2>;
116 clock-output-names = "atlclk", "aplclk","gpuclk";
118 scpi_clk: scpi_clocks@3 {
119 compatible = "arm,scpi-variable-clocks";
121 clock-indices = <3>, <4>;
122 clock-output-names = "pxlclk0", "pxlclk1";
130 clocks = <&scpi_dvfs 0>;
135 reg = <0 0x7ff60000 0 0x1000>;
136 clocks = <&scpi_clk 4>;
139 In the above example, the #clock-cells is set to 1 as required.
140 scpi_dvfs has 3 output clocks namely: atlclk, aplclk, and gpuclk with 0,
141 1 and 2 as clock-indices. scpi_clk has 2 output clocks namely: pxlclk0
142 and pxlclk1 with 3 and 4 as clock-indices.
144 The first consumer in the example is cpu@0 and it has '0' as the clock
145 specifier which points to the first entry in the output clocks of
146 scpi_dvfs i.e. "atlclk".
148 Similarly the second example is hdlcd@7ff60000 and it has pxlclk1 as input
149 clock. '4' in the clock specifier here points to the second entry
150 in the output clocks of scpi_clocks i.e. "pxlclk1"