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 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. 21 22See Documentation/devicetree/bindings/mailbox/mailbox.txt 23for more details about the generic mailbox controller and 24client driver bindings. 25 26Clock bindings for the clocks based on SCPI Message Protocol 27------------------------------------------------------------ 28 29This binding uses the common clock binding[1]. 30 31Container Node 32============== 33Required properties: 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. 37 38Sub-nodes 39========= 40Required properties: 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. 51 52Other 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. 58 59SRAM and Shared Memory for SCPI 60------------------------------- 61 62A small area of SRAM is reserved for SCPI communication between application 63processors and SCP. 64 65The properties should follow the generic mmio-sram description found in [3] 66 67Each sub-node represents the reserved area for SCPI. 68 69Required sub-node properties: 70- reg : The base offset and size of the reserved area with the SRAM 71- compatible : should be "arm,scp-shmem" for Non-secure SRAM based 72 shared memory 73 74Sensor bindings for the sensors based on SCPI Message Protocol 75-------------------------------------------------------------- 76SCPI provides an API to access the various sensors on the SoC. 77 78Required properties: 79- compatible : should be "arm,scpi-sensors". 80- #thermal-sensor-cells: should be set to 1. This property follows the 81 thermal device tree bindings[2]. 82 83 Valid cell values are raw identifiers (Sensor ID) 84 as used by the firmware. Refer to platform details 85 for your implementation for the IDs to use. 86 87Power domain bindings for the power domains based on SCPI Message Protocol 88------------------------------------------------------------ 89 90This binding uses the generic power domain binding[4]. 91 92PM domain providers 93=================== 94 95Required properties: 96 - #power-domain-cells : Should be 1. Contains the device or the power 97 domain ID value used by SCPI commands. 98 - num-domains: Total number of power domains provided by SCPI. This is 99 needed as the SCPI message protocol lacks a mechanism to 100 query this information at runtime. 101 102PM domain consumers 103=================== 104 105Required properties: 106 - power-domains : A phandle and PM domain specifier as defined by bindings of 107 the power controller specified by phandle. 108 109[0] http://infocenter.arm.com/help/topic/com.arm.doc.dui0922b/index.html 110[1] Documentation/devicetree/bindings/clock/clock-bindings.txt 111[2] Documentation/devicetree/bindings/thermal/thermal*.yaml 112[3] Documentation/devicetree/bindings/sram/sram.yaml 113[4] Documentation/devicetree/bindings/power/power-domain.yaml 114 115Example: 116 117sram: sram@50000000 { 118 compatible = "arm,juno-sram-ns", "mmio-sram"; 119 reg = <0x0 0x50000000 0x0 0x10000>; 120 121 #address-cells = <1>; 122 #size-cells = <1>; 123 ranges = <0 0x0 0x50000000 0x10000>; 124 125 cpu_scp_lpri: scp-shmem@0 { 126 compatible = "arm,juno-scp-shmem"; 127 reg = <0x0 0x200>; 128 }; 129 130 cpu_scp_hpri: scp-shmem@200 { 131 compatible = "arm,juno-scp-shmem"; 132 reg = <0x200 0x200>; 133 }; 134}; 135 136mailbox: mailbox0@40000000 { 137 .... 138 #mbox-cells = <1>; 139}; 140 141scpi_protocol: scpi@2e000000 { 142 compatible = "arm,scpi"; 143 mboxes = <&mailbox 0 &mailbox 1>; 144 shmem = <&cpu_scp_lpri &cpu_scp_hpri>; 145 146 clocks { 147 compatible = "arm,scpi-clocks"; 148 149 scpi_dvfs: scpi_clocks@0 { 150 compatible = "arm,scpi-dvfs-clocks"; 151 #clock-cells = <1>; 152 clock-indices = <0>, <1>, <2>; 153 clock-output-names = "atlclk", "aplclk","gpuclk"; 154 }; 155 scpi_clk: scpi_clocks@3 { 156 compatible = "arm,scpi-variable-clocks"; 157 #clock-cells = <1>; 158 clock-indices = <3>, <4>; 159 clock-output-names = "pxlclk0", "pxlclk1"; 160 }; 161 }; 162 163 scpi_sensors0: sensors { 164 compatible = "arm,scpi-sensors"; 165 #thermal-sensor-cells = <1>; 166 }; 167 168 scpi_devpd: scpi-power-domains { 169 compatible = "arm,scpi-power-domains"; 170 num-domains = <2>; 171 #power-domain-cells = <1>; 172 }; 173}; 174 175cpu@0 { 176 ... 177 reg = <0 0>; 178 clocks = <&scpi_dvfs 0>; 179}; 180 181hdlcd@7ff60000 { 182 ... 183 reg = <0 0x7ff60000 0 0x1000>; 184 clocks = <&scpi_clk 4>; 185 power-domains = <&scpi_devpd 1>; 186}; 187 188thermal-zones { 189 soc_thermal { 190 polling-delay-passive = <100>; 191 polling-delay = <1000>; 192 193 /* sensor ID */ 194 thermal-sensors = <&scpi_sensors0 3>; 195 ... 196 }; 197}; 198 199In the above example, the #clock-cells is set to 1 as required. 200scpi_dvfs has 3 output clocks namely: atlclk, aplclk, and gpuclk with 0, 2011 and 2 as clock-indices. scpi_clk has 2 output clocks namely: pxlclk0 202and pxlclk1 with 3 and 4 as clock-indices. 203 204The first consumer in the example is cpu@0 and it has '0' as the clock 205specifier which points to the first entry in the output clocks of 206scpi_dvfs i.e. "atlclk". 207 208Similarly the second example is hdlcd@7ff60000 and it has pxlclk1 as input 209clock. '4' in the clock specifier here points to the second entry 210in the output clocks of scpi_clocks i.e. "pxlclk1" 211 212The thermal-sensors property in the soc_thermal node uses the 213temperature sensor provided by SCP firmware to setup a thermal 214zone. The ID "3" is the sensor identifier for the temperature sensor 215as used by the firmware. 216 217The num-domains property in scpi-power-domains domain specifies that 218SCPI provides 2 power domains. The hdlcd node uses the power domain with 219domain ID 1. 220