Advanced Configuration and Power Interface Specification

Advanced Configuration and Power Interface Specification
}// End Device
9.20 NVDIMM Devices
In order to handle NVDIMMs, the OS must first be able to detect and enumerate the NVDIMMs. To
facilitate the plug and play discovery of NVDIMM and driver loading, ACPI Name Space devices
are used.
The ACPI Name Space device uses _HID of ACPI0012 to identify the root NVDIMM interface
device. Platform firmware is required to contain one such device in _SB scope if NVDIMMs support
is exposed by platform to OSPM. This device allows the OS to trigger enumeration of NVDIMMs
through NFIT at boot time and re-enumeration at root level via the _FIT method (refer to
Section 6.5.9) during runtime.
For each NVDIMM present or intended to be supported by platform, platform firmware also exposes
an ACPI Namespace Device under the root device. The NVDIMM ACPI Namespace Device
contains:
• _ADR object that is used to supply OSPM with unique address of the NVDIMM device. This is
done by returning the NFIT Device handle that is used to identify the associated entries in ACPI
table NFIT or _FIT.
An example name space is shown below for a platform containing 1 NVDIMM:
Scope (\_SB){
Device (NVDR) // Root device
{
Name (_HID, “ACPI0012”)
Method (_STA) {…}
Method (_FIT) {…}
Method (_DSM, …) {
…
}
}
}
Device (NVD)
{
Name(_ADR, h) //where h is NFIT Device Handle for this NVDIMM
Method (_DSM, …) {
…
}
}
NFIT Device Handle uniquely identifies a Memory Device in the above example and is constructed
using the DIMM number within the memory channel, memory channel number, memory controller
ID, Socket ID and, if applicable, Node Controller ID. Refer to Section 5.2.25 for details.
While this scheme allows for OS handling of NVDIMMs in a standard manner the format of the
address ranges described by this scheme may still vary depending on the vendor (or even different
NVDIMM version of the vendor). For example, Block NVDIMM Control Region format is vendor
specific and possibly even varies for a given vendor.
The NVDIMM Firmware Interface Table supports a concept of Vendor ID, Device ID, and Revision
ID. Since a NVDIMM could be a combination device consisting of different region types, for
example, Persistent Memory and Block, a Region Format Interface Code to comprehend the region
556 April, 2015 Version 6.0