1System Control and Power Interface (SCPI) Message Protocol 2---------------------------------------------------------- 3 4Firmware implementing the SCPI described in ARM document number ARM DUI 0922B 5("ARM Compute Subsystem SCP: Message Interface Protocols")[0] can be used 6by Linux to initiate various system control and power operations. 7 8Required properties: 9 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. 18 19See Documentation/devicetree/bindings/mailbox/mailbox.txt 20for more details about the generic mailbox controller and 21client driver bindings. 22 23Clock bindings for the clocks based on SCPI Message Protocol 24------------------------------------------------------------ 25 26This binding uses the common clock binding[1]. 27 28Container Node 29============== 30Required properties: 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. 34 35Sub-nodes 36========= 37Required properties: 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. 48 49Other 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. 55 56SRAM and Shared Memory for SCPI 57------------------------------- 58 59A small area of SRAM is reserved for SCPI communication between application 60processors and SCP. 61 62Required properties: 63- compatible : should be "arm,juno-sram-ns" for Non-secure SRAM on Juno 64 65The rest of the properties should follow the generic mmio-sram description 66found in ../../misc/sysram.txt 67 68Each sub-node represents the reserved area for SCPI. 69 70Required 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 74 75Sensor bindings for the sensors based on SCPI Message Protocol 76-------------------------------------------------------------- 77SCPI provides an API to access the various sensors on the SoC. 78 79Required properties: 80- compatible : should be "arm,scpi-sensors". 81- #thermal-sensor-cells: should be set to 1. This property follows the 82 thermal device tree bindings[2]. 83 84 Valid cell values are raw identifiers (Sensor 85 ID) as used by the firmware. Refer to 86 platform documentation for your 87 implementation for the IDs to use. For Juno 88 R0 and Juno R1 refer to [3]. 89 90[0] http://infocenter.arm.com/help/topic/com.arm.doc.dui0922b/index.html 91[1] Documentation/devicetree/bindings/clock/clock-bindings.txt 92[2] Documentation/devicetree/bindings/thermal/thermal.txt 93[3] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0922b/apas03s22.html 94 95Example: 96 97sram: sram@50000000 { 98 compatible = "arm,juno-sram-ns", "mmio-sram"; 99 reg = <0x0 0x50000000 0x0 0x10000>; 100 101 #address-cells = <1>; 102 #size-cells = <1>; 103 ranges = <0 0x0 0x50000000 0x10000>; 104 105 cpu_scp_lpri: scp-shmem@0 { 106 compatible = "arm,juno-scp-shmem"; 107 reg = <0x0 0x200>; 108 }; 109 110 cpu_scp_hpri: scp-shmem@200 { 111 compatible = "arm,juno-scp-shmem"; 112 reg = <0x200 0x200>; 113 }; 114}; 115 116mailbox: mailbox0@40000000 { 117 .... 118 #mbox-cells = <1>; 119}; 120 121scpi_protocol: scpi@2e000000 { 122 compatible = "arm,scpi"; 123 mboxes = <&mailbox 0 &mailbox 1>; 124 shmem = <&cpu_scp_lpri &cpu_scp_hpri>; 125 126 clocks { 127 compatible = "arm,scpi-clocks"; 128 129 scpi_dvfs: scpi_clocks@0 { 130 compatible = "arm,scpi-dvfs-clocks"; 131 #clock-cells = <1>; 132 clock-indices = <0>, <1>, <2>; 133 clock-output-names = "atlclk", "aplclk","gpuclk"; 134 }; 135 scpi_clk: scpi_clocks@3 { 136 compatible = "arm,scpi-variable-clocks"; 137 #clock-cells = <1>; 138 clock-indices = <3>, <4>; 139 clock-output-names = "pxlclk0", "pxlclk1"; 140 }; 141 }; 142 143 scpi_sensors0: sensors { 144 compatible = "arm,scpi-sensors"; 145 #thermal-sensor-cells = <1>; 146 }; 147}; 148 149cpu@0 { 150 ... 151 reg = <0 0>; 152 clocks = <&scpi_dvfs 0>; 153}; 154 155hdlcd@7ff60000 { 156 ... 157 reg = <0 0x7ff60000 0 0x1000>; 158 clocks = <&scpi_clk 4>; 159}; 160 161thermal-zones { 162 soc_thermal { 163 polling-delay-passive = <100>; 164 polling-delay = <1000>; 165 166 /* sensor ID */ 167 thermal-sensors = <&scpi_sensors0 3>; 168 ... 169 }; 170}; 171 172In the above example, the #clock-cells is set to 1 as required. 173scpi_dvfs has 3 output clocks namely: atlclk, aplclk, and gpuclk with 0, 1741 and 2 as clock-indices. scpi_clk has 2 output clocks namely: pxlclk0 175and pxlclk1 with 3 and 4 as clock-indices. 176 177The first consumer in the example is cpu@0 and it has '0' as the clock 178specifier which points to the first entry in the output clocks of 179scpi_dvfs i.e. "atlclk". 180 181Similarly the second example is hdlcd@7ff60000 and it has pxlclk1 as input 182clock. '4' in the clock specifier here points to the second entry 183in the output clocks of scpi_clocks i.e. "pxlclk1" 184 185The thermal-sensors property in the soc_thermal node uses the 186temperature sensor provided by SCP firmware to setup a thermal 187zone. The ID "3" is the sensor identifier for the temperature sensor 188as used by the firmware. 189