EC Firmware Management

This service is to provide details about the security state, supported features, debug, firmware version and firmware update functionality.

NIST SP 800-193 compliance requires failsafe update of primary and backup EC FW images. EC should run from primary partition while writing backup partitions and then change flag to indicate backup becomes primary and primary becomes backup.

Get Firmware State

Returns start of the overall EC if DICE and secure boot was enabled, currently running firmware version, EC status like boot failures.

Secure Boot and DICE

DICE is a specification from the Trusted Computing Group that allows the MCU to verify the signature of the code that it is executing, thereby establishing trust in the code. To do this, it has a primary bootloader program that reads the firmware on flash and using a key that is only accessible by the ROM bootloader, can verify the authenticity of the firmware. 

Trusted Platform Architecture - Device Identity Composition Engine (trustedcomputinggroup.org) 

Input Parameters

None

Output Parameters

FFA ACPI Example

Method (TFWS) {
  // Check to make sure FFA is available and not unloaded
  If(LEqual(\\_SB.FFA0.AVAL,One)) {
    CreateQwordField(BUFF,0,STAT) // Out – Status for req/rsp
    CreateField(BUFF,128,128,UUID) // UUID of service
    CreateByteField(BUFF,32, CMDD) // In – First byte of command
    CreateDwordField(BUFF,32,FWSD) // Out – Raw data response (overlaps with CMDD)

    Store(ToUUID("330c1273-fde5-4757-9819-5b6539037502"), UUID) // Management
    Store(0x1, CMDD) // EC_CAP_GET_FW_STATE
    Store(Store(BUFF, \_SB_.FFA0.FFAC), BUFF)

    If(LEqual(STAT,0x0) ) // Check FF-A successful?
    {
      Return (FWSD)
    } 
  }
  Return(Zero)
}

Get Features Supported

Get a list of services/features supported by this EC. Several features like HID devices are optional and may not be present. OEM services may also be added to this list as additional features supported.

Input Parameters

None

Output Parameters

FFA ACPI Example

Method(TFET, 0x0, Serialized) {
  If(LEqual(\\_SB.FFA0.AVAL,One)) {
    CreateQwordField(BUFF,0,STAT) // Out – Status for req/rsp
    CreateField(BUFF,128,128,UUID) // UUID of service
    CreateByteField(BUFF,32, CMDD) // In – First byte of command
    CreateWordField(BUFF,32,FET0) // DebugMask
    CreateByteField(BUFF,34,FET1) // BatteryMask
    CreateByteField(BUFF,35,FET2) // FanMask
    CreateByteField(BUFF,36,FET3) // ThermalMask
    CreateByteField(BUFF,37,FET4) // HIDMask
    CreateWordField(BUFF,38,FET5) // KeyMask

    Store(0x2, CMDD) // EC_CAP_GET_SVC_LIST
    Store(ToUUID("330c1273-fde5-4757-9819-5b6539037502"), UUID)
    Store(Store(BUFF, \\_SB_.FFA0.FFAC), BUFF)

    If(LEqual(STAT,0x0) ) {
      Return (package () {FET0,FET1,FET2,FET3,FET4,FET5})
    }
  }
  Return(package () {0,0,0,0,0,0,0})
}

Get Board ID

EC is often used to read pins or details to determine the HW configuration based on GPIO’s or ADC values. This ID allows SW to change behavior depending on this HW version information.

Input Parameters

None

Output Parameters

FFA ACPI Example

Method(TBID, 0x0, Serialized) {
  If(LEqual(\\_SB.FFA0.AVAL,One)) {
    CreateQwordField(BUFF,0,STAT) // Out – Status for req/rsp
    CreateField(BUFF,128,128,UUID) // UUID of service
    CreateByteField(BUFF,32, CMDD) // In – First byte of command
    CreateDwordField(BUFF,32,BIDD) // Output Data

    Store(0x3, CMDD) // EC_CAP_GET_BID
    Store(ToUUID("330c1273-fde5-4757-9819-5b6539037502"), UUID)
    Store(Store(BUFF, \\_SB_.FFA0.FFAC), BUFF)

    If(LEqual(STAT,0x0) ) {
      Return (BIDD)
    } else {
  }
  Return(Zero)
}

Firmware Update

This should initiate update of a particular firmware in the backup partition to provide NIST SP 800-193 failsafe compliance. EC firmware update is planned to be handled through CFU. Further details are available in CFU specification.