Advanced Configuration and Power Interface Specification

Device Configuration
APIC Device”. Any I/O APIC device that either supports hot-plug or is not described in the MADT
must contain a _GSB object.
If the I/O APIC device also contains a _MAT object, OSPM evaluates the _GSB object first before
evaluating the _MAT object. By providing the Global System Interrupt Base of the I/O APIC, this
object enables OSPM to process only the _MAT entries that correspond to the I/O APIC device. See
Section 6.2.10, “_MAT (Multiple APIC Table Entry)”. Since _MAT is allowed to potentially return
all the MADT entries for the entire platform, _GSB is needed in the I/O APIC device scope to enable
OSPM to identify the entries that correspond to that device.
If an I/O APIC device is activated by a device-specific driver, the physical address used to access the
I/O APIC will be exposed by the driver and cannot be determined from the _MAT object. In this
case, OSPM cannot use the _MAT object to determine the Global System Interrupt Base
corresponding to the I/O APIC device and hence requires the _GSB object.
The Global System Interrupt Base is a 64-bit value representing the corresponding I/OAPIC device
as defined in Section 5.2.13, “Global System Interrupts”.
Arguments:
None
Return Value:
An Integer containing the interrupt base
Example ASL for _GSB usage for a non-PCI based I/O APIC Device:
Scope(\_SB) {
…
Device(APIC) {
// I/O APIC Device
Name(_HID, “ACPI0009”)
// ACPI ID for I/O APIC
Name(_CRS, ResourceTemplate()
{ …}) // only one resource pointing to I/O APIC register base
Method(_GSB){
Return (0x10) // Global System Interrupt Base for I/O APIC starts at 16
}
} // end APIC
} // end scope SB
Example ASL for _GSB usage for a PCI-based I/O APIC Device:
Scope(\_SB) {
Device(PCI0)
// Host bridge
Name(_HID, EISAID("PNP0A03")) // Need _HID for root device
Device(PCI1) {
// I/O APIC PCI Device
Name(_ADR,0x00070000)
Method(_GSB){
Return (0x18) // Global System Interrupt Base for I/O APIC starts at 24
}
} // end PCI1
} // end PCI0
} // end scope SB
6.2.8 _HPP (Hot Plug Parameters)
This optional object evaluates to a package containing the cache-line size, latency timer, SERR
enable, and PERR enable values to be used when configuring a PCI device inserted into a hot-plug
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