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Diffstat (limited to 'Documentation/devicetree/bindings/powerpc/opal/power-mgt.txt')
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diff --git a/Documentation/devicetree/bindings/powerpc/opal/power-mgt.txt b/Documentation/devicetree/bindings/powerpc/opal/power-mgt.txt new file mode 100644 index 000000000..d6658d3dd --- /dev/null +++ b/Documentation/devicetree/bindings/powerpc/opal/power-mgt.txt @@ -0,0 +1,118 @@ +IBM Power-Management Bindings +============================= + +Linux running on baremetal POWER machines has access to the processor +idle states. The description of these idle states is exposed via the +node @power-mgt in the device-tree by the firmware. + +Definitions: +---------------- +Typically each idle state has the following associated properties: + +- name: The name of the idle state as defined by the firmware. + +- flags: indicating some aspects of this idle states such as the + extent of state-loss, whether timebase is stopped on this + idle states and so on. The flag bits are as follows: + +- exit-latency: The latency involved in transitioning the state of the + CPU from idle to running. + +- target-residency: The minimum time that the CPU needs to reside in + this idle state in order to accrue power-savings + benefit. + +Properties +---------------- +The following properties provide details about the idle states. These +properties are exposed as arrays. Each entry in the property array +provides the value of that property for the idle state associated with +the array index of that entry. + +If idle-states are defined, then the properties +"ibm,cpu-idle-state-names" and "ibm,cpu-idle-state-flags" are +required. The other properties are required unless mentioned +otherwise. The length of all the property arrays must be the same. + +- ibm,cpu-idle-state-names: + Array of strings containing the names of the idle states. + +- ibm,cpu-idle-state-flags: + Array of unsigned 32-bit values containing the values of the + flags associated with the aforementioned idle-states. The + flag bits are as follows: + 0x00000001 /* Decrementer would stop */ + 0x00000002 /* Needs timebase restore */ + 0x00001000 /* Restore GPRs like nap */ + 0x00002000 /* Restore hypervisor resource from PACA pointer */ + 0x00004000 /* Program PORE to restore PACA pointer */ + 0x00010000 /* This is a nap state (POWER7,POWER8) */ + 0x00020000 /* This is a fast-sleep state (POWER8)*/ + 0x00040000 /* This is a winkle state (POWER8) */ + 0x00080000 /* This is a fast-sleep state which requires a */ + /* software workaround for restoring the */ + /* timebase (POWER8) */ + 0x00800000 /* This state uses SPR PMICR instruction */ + /* (POWER8)*/ + 0x00100000 /* This is a fast stop state (POWER9) */ + 0x00200000 /* This is a deep-stop state (POWER9) */ + +- ibm,cpu-idle-state-latencies-ns: + Array of unsigned 32-bit values containing the values of the + exit-latencies (in ns) for the idle states in + ibm,cpu-idle-state-names. + +- ibm,cpu-idle-state-residency-ns: + Array of unsigned 32-bit values containing the values of the + target-residency (in ns) for the idle states in + ibm,cpu-idle-state-names. On POWER8 this is an optional + property. If the property is absent, the target residency for + the "Nap", "FastSleep" are defined to 10000 and 300000000 + respectively by the kernel. On POWER9 this property is required. + +- ibm,cpu-idle-state-psscr: + Array of unsigned 64-bit values containing the values for the + PSSCR for each of the idle states in ibm,cpu-idle-state-names. + This property is required on POWER9 and absent on POWER8. + +- ibm,cpu-idle-state-psscr-mask: + Array of unsigned 64-bit values containing the masks + indicating which psscr fields are set in the corresponding + entries of ibm,cpu-idle-state-psscr. This property is + required on POWER9 and absent on POWER8. + + Whenever the firmware sets an entry in + ibm,cpu-idle-state-psscr-mask value to 0xf, it implies that + only the Requested Level (RL) field of the corresponding entry + in ibm,cpu-idle-state-psscr should be considered by the + kernel. For such idle states, the kernel would set the + remaining fields of the psscr to the following sane-default + values. + + - ESL and EC bits are to 1. So wakeup from any stop + state will be at vector 0x100. + + - MTL and PSLL are set to the maximum allowed value as + per the ISA, i.e. 15. + + - The Transition Rate, TR is set to the Maximum value + 3. + + For all the other values of the entry in + ibm,cpu-idle-state-psscr-mask, the kernel expects all the + psscr fields of the corresponding entry in + ibm,cpu-idle-state-psscr to be correctly set by the firmware. + +- ibm,cpu-idle-state-pmicr: + Array of unsigned 64-bit values containing the pmicr values + for the idle states in ibm,cpu-idle-state-names. This 64-bit + register value is to be set in pmicr for the corresponding + state if the flag indicates that pmicr SPR should be set. This + is an optional property on POWER8 and is absent on + POWER9. + +- ibm,cpu-idle-state-pmicr-mask: + Array of unsigned 64-bit values containing the mask indicating + which of the fields of the PMICR are set in the corresponding + entries in ibm,cpu-idle-state-pmicr. This is an optional + property on POWER8 and is absent on POWER9. |