ACPI Thermal Management

This page captures an investigation into ACPI thermal management support with active and passive cooling.

Status

Implemented thermal zones and properties required for active (FAN) and passive (CPUFreq) cooling in RD-N2 platform.
- https://gitlab.com/LinaroLtd/clientpc/edk2-platforms/-/commit/c6c79ce526a3104702e132e8a04010fdd054b55d
Investigated Linux kernel support and proposed a patch to fix issues with passive cooling
- https://gitlab.com/LinaroLtd/clientpc/linux/-/commits/thermal_acpi

Example Thermal Zone implementation in RD-N2

//FAN0
Name(FNS0,0)
PowerResource(FN00, 0, 0)
{
    Method(_STA, 0, Serialized)
    {
        Return(FNS0)
    }

    Method(_ON, 0, Serialized)
    {
        printf ("Debug: Fan 0 on")
        Store(1,FNS0)
    }

    Method(_OFF, 0, Serialized)
    {
        printf ("Debug: Fan 0 off")
        Store(0,FNS0)
    }
}

Device(FAN0)
{
    Name(_HID, EISAID("PNP0C0B"))
    Name(_UID,0)
    Name(_PR0, Package(1){FN00})
}
//FAN1
Name(FNS1,0)
PowerResource(FN01, 0, 0)
{
    Method(_STA, 0, Serialized)
    {
        Return(FNS1)
    }
    Method(_ON, 0, Serialized)
    {
        printf ("Debug: Fan 1 on")
        Store(1,FNS1)
    }
    Method(_OFF, 0, Serialized)
    {
        printf ("Debug: Fan 1 off")
        Store(0,FNS1)
    }
}

Device(FAN1)
{
    Name(_HID, EISAID("PNP0C0B"))
    Name(_UID,1)
    Name(_PR0, Package(1){FN01})
}
//ThermalZone0
Name(TMP1,3000)
ThermalZone(TZ00){
    Method(_CRT) { Return(3880) }//114.85
    Name(_TZP, 300)
    //
    Method(_AC0) { Return (3350)}//51.85
    Name(_AL0, Package(){FAN0})
    //
    Method(_PSV) { Return(3500) }//76.85
    Method(_TC1) { Return (4) }
    Method(_TC2) { Return (3) }
    Method(_TSP) { Return (10) }
    Method(_PSL, 0, Serialized){ Return( Package(){\_SB.CL00.CP00, \_SB.CL01.CP01, \_SB.CL02.CP02, \_SB.CL03.CP03,  \_SB.CL04.CP04,  \_SB.CL05.CP05,  \_SB.CL06.CP06} )}
    Method(_SCP, 1, Serialized)
    {
        If(LEqual(Arg0,0)){
            printf ("Debug: Active cooling")
        }ElseIf(LEqual(Arg0,1)){
            printf ("Debug: Passive cooling")
        }
    }

    Method(_TMP, 0, Serialized)
    {
        If(TMP1 < 3600){
            Add(TMP1,20,TMP1)
        }Else{
            TMP1 = 3000
        }
        Return(TMP1)
    }
}

//ThermalZone1
Name(TMP2,3000)
ThermalZone(TZ01){
    Method(_CRT) { Return(3880) }//114.85
    Name(_TZP, 300)
    //
    Method(_AC0) { Return (3350)}//51.85
    Name(_AL0, Package(){FAN1})
    //
    Method(_PSV) { Return(3500) }//76.85
    Method(_TC1) { Return (4) }
    Method(_TC2) { Return (3) }
    Method(_TSP) { Return (10) }
    Method(_PSL, 0, Serialized){ Return( Package(){\_SB.CL07.CP07, \_SB.CL08.CP08} )}
    Method(_SCP, 1, Serialized)
    {
        If(LEqual(Arg0,0)){
            printf ("Debug: Active cooling")
        }ElseIf(LEqual(Arg0,1)){
            printf ("Debug: Passive cooling")
        }
    }

    Method(_TMP, 0, Serialized)
    {
        If(TMP2 < 3600){
            Add(TMP2,20,TMP2)
        }Else{
            TMP2 = 3000
        }
        Return(TMP2)
    }
}

Required properties for passive cooling

ThermalZones need to be defined
_CRT, _HOT, _PSV, _TZP, _PSL needs to be defined
_TC1, _TC2, and _TSP needs to be defined
_PTC, _TSS and _TPC are not required

ACPI Thermal Management Demo with active and passive cooling

https://linaro.atlassian.net/wiki/spaces/CLIENTPC/pages/28821979154

ACPI Processor Clock Throttling

https://linaro.atlassian.net/wiki/spaces/CLIENTPC/pages/28855173127