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-rw-r--r--Documentation/arm64/acpi_object_usage.txt343
1 files changed, 186 insertions, 157 deletions
diff --git a/Documentation/arm64/acpi_object_usage.txt b/Documentation/arm64/acpi_object_usage.txt
index a6e1a1805e51..c77010c5c1f0 100644
--- a/Documentation/arm64/acpi_object_usage.txt
+++ b/Documentation/arm64/acpi_object_usage.txt
@@ -13,14 +13,14 @@ For ACPI on arm64, tables also fall into the following categories:
-- Required: DSDT, FADT, GTDT, MADT, MCFG, RSDP, SPCR, XSDT
- -- Recommended: BERT, EINJ, ERST, HEST, SSDT
+ -- Recommended: BERT, EINJ, ERST, HEST, PCCT, SSDT
- -- Optional: BGRT, CPEP, CSRT, DRTM, ECDT, FACS, FPDT, MCHI, MPST,
- MSCT, RASF, SBST, SLIT, SPMI, SRAT, TCPA, TPM2, UEFI
-
- -- Not supported: BOOT, DBG2, DBGP, DMAR, ETDT, HPET, IBFT, IVRS,
- LPIT, MSDM, RSDT, SLIC, WAET, WDAT, WDRT, WPBT
+ -- Optional: BGRT, CPEP, CSRT, DBG2, DRTM, ECDT, FACS, FPDT, IORT,
+ MCHI, MPST, MSCT, NFIT, PMTT, RASF, SBST, SLIT, SPMI, SRAT, STAO,
+ TCPA, TPM2, UEFI, XENV
+ -- Not supported: BOOT, DBGP, DMAR, ETDT, HPET, IBFT, IVRS, LPIT,
+ MSDM, OEMx, PSDT, RSDT, SLIC, WAET, WDAT, WDRT, WPBT
Table Usage for ARMv8 Linux
----- ----------------------------------------------------------------
@@ -50,7 +50,8 @@ CSRT Signature Reserved (signature == "CSRT")
DBG2 Signature Reserved (signature == "DBG2")
== DeBuG port table 2 ==
- Microsoft only table, will not be supported.
+ License has changed and should be usable. Optional if used instead
+ of earlycon=<device> on the command line.
DBGP Signature Reserved (signature == "DBGP")
== DeBuG Port table ==
@@ -133,10 +134,11 @@ GTDT Section 5.2.24 (signature == "GTDT")
HEST Section 18.3.2 (signature == "HEST")
== Hardware Error Source Table ==
- Until further error source types are defined, use only types 6 (AER
- Root Port), 7 (AER Endpoint), 8 (AER Bridge), or 9 (Generic Hardware
- Error Source). Firmware first error handling is possible if and only
- if Trusted Firmware is being used on arm64.
+ ARM-specific error sources have been defined; please use those or the
+ PCI types such as type 6 (AER Root Port), 7 (AER Endpoint), or 8 (AER
+ Bridge), or use type 9 (Generic Hardware Error Source). Firmware first
+ error handling is possible if and only if Trusted Firmware is being
+ used on arm64.
Must be supplied if RAS support is provided by the platform. It
is recommended this table be supplied.
@@ -149,20 +151,30 @@ IBFT Signature Reserved (signature == "IBFT")
== iSCSI Boot Firmware Table ==
Microsoft defined table, support TBD.
+IORT Signature Reserved (signature == "IORT")
+ == Input Output Remapping Table ==
+ arm64 only table, required in order to describe IO topology, SMMUs,
+ and GIC ITSs, and how those various components are connected together,
+ such as identifying which components are behind which SMMUs/ITSs.
+ This table will only be required on certain SBSA platforms (e.g.,
+ when using GICv3-ITS and an SMMU); on SBSA Level 0 platforms, it
+ remains optional.
+
IVRS Signature Reserved (signature == "IVRS")
== I/O Virtualization Reporting Structure ==
x86_64 (AMD) only table, will not be supported.
LPIT Signature Reserved (signature == "LPIT")
== Low Power Idle Table ==
- x86 only table as of ACPI 5.1; future versions have been adapted for
- use with ARM and will be recommended in order to support ACPI power
- management.
+ x86 only table as of ACPI 5.1; starting with ACPI 6.0, processor
+ descriptions and power states on ARM platforms should use the DSDT
+ and define processor container devices (_HID ACPI0010, Section 8.4,
+ and more specifically 8.4.3 and and 8.4.4).
MADT Section 5.2.12 (signature == "APIC")
== Multiple APIC Description Table ==
Required for arm64. Only the GIC interrupt controller structures
- should be used (types 0xA - 0xE).
+ should be used (types 0xA - 0xF).
MCFG Signature Reserved (signature == "MCFG")
== Memory-mapped ConFiGuration space ==
@@ -176,14 +188,38 @@ MPST Section 5.2.21 (signature == "MPST")
== Memory Power State Table ==
Optional, not currently supported.
+MSCT Section 5.2.19 (signature == "MSCT")
+ == Maximum System Characteristic Table ==
+ Optional, not currently supported.
+
MSDM Signature Reserved (signature == "MSDM")
== Microsoft Data Management table ==
Microsoft only table, will not be supported.
-MSCT Section 5.2.19 (signature == "MSCT")
- == Maximum System Characteristic Table ==
+NFIT Section 5.2.25 (signature == "NFIT")
+ == NVDIMM Firmware Interface Table ==
+ Optional, not currently supported.
+
+OEMx Signature of "OEMx" only
+ == OEM Specific Tables ==
+ All tables starting with a signature of "OEM" are reserved for OEM
+ use. Since these are not meant to be of general use but are limited
+ to very specific end users, they are not recommended for use and are
+ not supported by the kernel for arm64.
+
+PCCT Section 14.1 (signature == "PCCT)
+ == Platform Communications Channel Table ==
+ Recommend for use on arm64; use of PCC is recommended when using CPPC
+ to control performance and power for platform processors.
+
+PMTT Section 5.2.21.12 (signature == "PMTT")
+ == Platform Memory Topology Table ==
Optional, not currently supported.
+PSDT Section 5.2.11.3 (signature == "PSDT")
+ == Persistent System Description Table ==
+ Obsolete table, will not be supported.
+
RASF Section 5.2.20 (signature == "RASF")
== RAS Feature table ==
Optional, not currently supported.
@@ -195,7 +231,7 @@ RSDP Section 5.2.5 (signature == "RSD PTR")
RSDT Section 5.2.7 (signature == "RSDT")
== Root System Description Table ==
Since this table can only provide 32-bit addresses, it is deprecated
- on arm64, and will not be used.
+ on arm64, and will not be used. If provided, it will be ignored.
SBST Section 5.2.14 (signature == "SBST")
== Smart Battery Subsystem Table ==
@@ -220,7 +256,7 @@ SPMI Signature Reserved (signature == "SPMI")
SRAT Section 5.2.16 (signature == "SRAT")
== System Resource Affinity Table ==
Optional, but if used, only the GICC Affinity structures are read.
- To support NUMA, this table is required.
+ To support arm64 NUMA, this table is required.
SSDT Section 5.2.11.2 (signature == "SSDT")
== Secondary System Description Table ==
@@ -235,6 +271,11 @@ SSDT Section 5.2.11.2 (signature == "SSDT")
These tables are optional, however. ACPI tables should contain only
one DSDT but can contain many SSDTs.
+STAO Signature Reserved (signature == "STAO")
+ == _STA Override table ==
+ Optional, but only necessary in virtualized environments in order to
+ hide devices from guest OSs.
+
TCPA Signature Reserved (signature == "TCPA")
== Trusted Computing Platform Alliance table ==
Optional, not currently supported, and may need changes to fully
@@ -266,6 +307,10 @@ WPBT Signature Reserved (signature == "WPBT")
== Windows Platform Binary Table ==
Microsoft only table, will not be supported.
+XENV Signature Reserved (signature == "XENV")
+ == Xen project table ==
+ Optional, used only by Xen at present.
+
XSDT Section 5.2.8 (signature == "XSDT")
== eXtended System Description Table ==
Required for arm64.
@@ -273,44 +318,46 @@ XSDT Section 5.2.8 (signature == "XSDT")
ACPI Objects
------------
-The expectations on individual ACPI objects are discussed in the list that
-follows:
+The expectations on individual ACPI objects that are likely to be used are
+shown in the list that follows; any object not explicitly mentioned below
+should be used as needed for a particular platform or particular subsystem,
+such as power management or PCI.
Name Section Usage for ARMv8 Linux
---- ------------ -------------------------------------------------
-_ADR 6.1.1 Use as needed.
-
-_BBN 6.5.5 Use as needed; PCI-specific.
+_CCA 6.2.17 This method must be defined for all bus masters
+ on arm64 -- there are no assumptions made about
+ whether such devices are cache coherent or not.
+ The _CCA value is inherited by all descendants of
+ these devices so it does not need to be repeated.
+ Without _CCA on arm64, the kernel does not know what
+ to do about setting up DMA for the device.
-_BDN 6.5.3 Optional; not likely to be used on arm64.
+ NB: this method provides default cache coherency
+ attributes; the presence of an SMMU can be used to
+ modify that, however. For example, a master could
+ default to non-coherent, but be made coherent with
+ the appropriate SMMU configuration (see Table 17 of
+ the IORT specification, ARM Document DEN 0049B).
-_CCA 6.2.17 This method should be defined for all bus masters
- on arm64. While cache coherency is assumed, making
- it explicit ensures the kernel will set up DMA as
- it should.
+_CID 6.1.2 Use as needed, see also _HID.
-_CDM 6.2.1 Optional, to be used only for processor devices.
+_CLS 6.1.3 Use as needed, see also _HID.
-_CID 6.1.2 Use as needed.
-
-_CLS 6.1.3 Use as needed.
+_CPC 8.4.7.1 Use as needed, power management specific. CPPC is
+ recommended on arm64.
_CRS 6.2.2 Required on arm64.
-_DCK 6.5.2 Optional; not likely to be used on arm64.
+_CSD 8.4.2.2 Use as needed, used only in conjunction with _CST.
+
+_CST 8.4.2.1 Low power idle states (8.4.4) are recommended instead
+ of C-states.
_DDN 6.1.4 This field can be used for a device name. However,
it is meant for DOS device names (e.g., COM1), so be
careful of its use across OSes.
-_DEP 6.5.8 Use as needed.
-
-_DIS 6.2.3 Optional, for power management use.
-
-_DLM 5.7.5 Optional.
-
-_DMA 6.2.4 Optional.
-
_DSD 6.2.5 To be used with caution. If this object is used, try
to use it within the constraints already defined by the
Device Properties UUID. Only in rare circumstances
@@ -325,20 +372,10 @@ _DSD 6.2.5 To be used with caution. If this object is used, try
with the UEFI Forum; this may cause some iteration as
more than one OS will be registering entries.
-_DSM Do not use this method. It is not standardized, the
+_DSM 9.1.1 Do not use this method. It is not standardized, the
return values are not well documented, and it is
currently a frequent source of error.
-_DSW 7.2.1 Use as needed; power management specific.
-
-_EDL 6.3.1 Optional.
-
-_EJD 6.3.2 Optional.
-
-_EJx 6.3.3 Optional.
-
-_FIX 6.2.7 x86 specific, not used on arm64.
-
\_GL 5.7.1 This object is not to be used in hardware reduced
mode, and therefore should not be used on arm64.
@@ -349,35 +386,22 @@ _GLK 6.5.7 This object requires a global lock be defined; there
\_GPE 5.3.1 This namespace is for x86 use only. Do not use it
on arm64.
-_GSB 6.2.7 Optional.
-
-_HID 6.1.5 Use as needed. This is the primary object to use in
- device probing, though _CID and _CLS may also be used.
-
-_HPP 6.2.8 Optional, PCI specific.
-
-_HPX 6.2.9 Optional, PCI specific.
-
-_HRV 6.1.6 Optional, use as needed to clarify device behavior; in
- some cases, this may be easier to use than _DSD.
+_HID 6.1.5 This is the primary object to use in device probing,
+ though _CID and _CLS may also be used.
_INI 6.5.1 Not required, but can be useful in setting up devices
when UEFI leaves them in a state that may not be what
the driver expects before it starts probing.
-_IRC 7.2.15 Use as needed; power management specific.
-
-_LCK 6.3.4 Optional.
-
-_MAT 6.2.10 Optional; see also the MADT.
+_LPI 8.4.4.3 Recommended for use with processor definitions (_HID
+ ACPI0010) on arm64. See also _RDI.
-_MLS 6.1.7 Optional, but highly recommended for use in
- internationalization.
+_MLS 6.1.7 Highly recommended for use in internationalization.
-_OFF 7.1.2 It is recommended to define this method for any device
+_OFF 7.2.2 It is recommended to define this method for any device
that can be turned on or off.
-_ON 7.1.3 It is recommended to define this method for any device
+_ON 7.2.3 It is recommended to define this method for any device
that can be turned on or off.
\_OS 5.7.3 This method will return "Linux" by default (this is
@@ -398,122 +422,107 @@ _OSC 6.2.11 This method can be a global method in ACPI (i.e.,
by the kernel community, then register it with the
UEFI Forum.
-\_OSI 5.7.2 Deprecated on ARM64. Any invocation of this method
- will print a warning on the console and return false.
- That is, as far as ACPI firmware is concerned, _OSI
- cannot be used to determine what sort of system is
- being used or what functionality is provided. The
- _OSC method is to be used instead.
-
-_OST 6.3.5 Optional.
+\_OSI 5.7.2 Deprecated on ARM64. As far as ACPI firmware is
+ concerned, _OSI is not to be used to determine what
+ sort of system is being used or what functionality
+ is provided. The _OSC method is to be used instead.
_PDC 8.4.1 Deprecated, do not use on arm64.
\_PIC 5.8.1 The method should not be used. On arm64, the only
interrupt model available is GIC.
-_PLD 6.1.8 Optional.
-
\_PR 5.3.1 This namespace is for x86 use only on legacy systems.
Do not use it on arm64.
-_PRS 6.2.12 Optional.
-
_PRT 6.2.13 Required as part of the definition of all PCI root
devices.
-_PRW 7.2.13 Use as needed; power management specific.
-
-_PRx 7.2.8-11 Use as needed; power management specific. If _PR0 is
+_PRx 7.3.8-11 Use as needed; power management specific. If _PR0 is
defined, _PR3 must also be defined.
-_PSC 7.2.6 Use as needed; power management specific.
-
-_PSE 7.2.7 Use as needed; power management specific.
-
-_PSW 7.2.14 Use as needed; power management specific.
-
-_PSx 7.2.2-5 Use as needed; power management specific. If _PS0 is
+_PSx 7.3.2-5 Use as needed; power management specific. If _PS0 is
defined, _PS3 must also be defined. If clocks or
regulators need adjusting to be consistent with power
usage, change them in these methods.
-\_PTS 7.3.1 Use as needed; power management specific.
-
-_PXM 6.2.14 Optional.
-
-_REG 6.5.4 Use as needed.
+_RDI 8.4.4.4 Recommended for use with processor definitions (_HID
+ ACPI0010) on arm64. This should only be used in
+ conjunction with _LPI.
\_REV 5.7.4 Always returns the latest version of ACPI supported.
-_RMV 6.3.6 Optional.
-
\_SB 5.3.1 Required on arm64; all devices must be defined in this
namespace.
-_SEG 6.5.6 Use as needed; PCI-specific.
-
-\_SI 5.3.1, Optional.
- 9.1
-
-_SLI 6.2.15 Optional; recommended when SLIT table is in use.
+_SLI 6.2.15 Use is recommended when SLIT table is in use.
_STA 6.3.7, It is recommended to define this method for any device
- 7.1.4 that can be turned on or off.
+ 7.2.4 that can be turned on or off. See also the STAO table
+ that provides overrides to hide devices in virtualized
+ environments.
-_SRS 6.2.16 Optional; see also _PRS.
+_SRS 6.2.16 Use as needed; see also _PRS.
_STR 6.1.10 Recommended for conveying device names to end users;
this is preferred over using _DDN.
_SUB 6.1.9 Use as needed; _HID or _CID are preferred.
-_SUN 6.1.11 Optional.
-
-\_Sx 7.3.2 Use as needed; power management specific.
-
-_SxD 7.2.16-19 Use as needed; power management specific.
-
-_SxW 7.2.20-24 Use as needed; power management specific.
+_SUN 6.1.11 Use as needed, but recommended.
-_SWS 7.3.3 Use as needed; power management specific; this may
+_SWS 7.4.3 Use as needed; power management specific; this may
require specification changes for use on arm64.
-\_TTS 7.3.4 Use as needed; power management specific.
-
-\_TZ 5.3.1 Optional.
-
_UID 6.1.12 Recommended for distinguishing devices of the same
class; define it if at all possible.
-\_WAK 7.3.5 Use as needed; power management specific.
+
ACPI Event Model
----------------
Do not use GPE block devices; these are not supported in the hardware reduced
profile used by arm64. Since there are no GPE blocks defined for use on ARM
-platforms, GPIO-signaled interrupts should be used for creating system events.
+platforms, ACPI events must be signaled differently.
+
+There are two options: GPIO-signaled interrupts (Section 5.6.5), and
+interrupt-signaled events (Section 5.6.9). Interrupt-signaled events are a
+new feature in the ACPI 6.1 specification. Either -- or both -- can be used
+on a given platform, and which to use may be dependent of limitations in any
+given SoC. If possible, interrupt-signaled events are recommended.
ACPI Processor Control
----------------------
-Section 8 of the ACPI specification is currently undergoing change that
-should be completed in the 6.0 version of the specification. Processor
-performance control will be handled differently for arm64 at that point
-in time. Processor aggregator devices (section 8.5) will not be used,
-for example, but another similar mechanism instead.
-
-While UEFI constrains what we can say until the release of 6.0, it is
-recommended that CPPC (8.4.5) be used as the primary model. This will
-still be useful into the future. C-states and P-states will still be
-provided, but most of the current design work appears to favor CPPC.
+Section 8 of the ACPI specification changed significantly in version 6.0.
+Processors should now be defined as Device objects with _HID ACPI0007; do
+not use the deprecated Processor statement in ASL. All multiprocessor systems
+should also define a hierarchy of processors, done with Processor Container
+Devices (see Section 8.4.3.1, _HID ACPI0010); do not use processor aggregator
+devices (Section 8.5) to describe processor topology. Section 8.4 of the
+specification describes the semantics of these object definitions and how
+they interrelate.
+
+Most importantly, the processor hierarchy defined also defines the low power
+idle states that are available to the platform, along with the rules for
+determining which processors can be turned on or off and the circumstances
+that control that. Without this information, the processors will run in
+whatever power state they were left in by UEFI.
+
+Note too, that the processor Device objects defined and the entries in the
+MADT for GICs are expected to be in synchronization. The _UID of the Device
+object must correspond to processor IDs used in the MADT.
+
+It is recommended that CPPC (8.4.5) be used as the primary model for processor
+performance control on arm64. C-states and P-states may become available at
+some point in the future, but most current design work appears to favor CPPC.
Further, it is essential that the ARMv8 SoC provide a fully functional
implementation of PSCI; this will be the only mechanism supported by ACPI
-to control CPU power state (including secondary CPU booting).
-
-More details will be provided on the release of the ACPI 6.0 specification.
+to control CPU power state. Booting of secondary CPUs using the ACPI
+parking protocol is possible, but discouraged, since only PSCI is supported
+for ARM servers.
ACPI System Address Map Interfaces
@@ -535,21 +544,25 @@ used to indicate fatal errors that cannot be corrected, and require immediate
attention.
Since there is no direct equivalent of the x86 SCI or NMI, arm64 handles
-these slightly differently. The SCI is handled as a normal GPIO-signaled
-interrupt; given that these are corrected (or correctable) errors being
-reported, this is sufficient. The NMI is emulated as the highest priority
-GPIO-signaled interrupt possible. This implies some caution must be used
-since there could be interrupts at higher privilege levels or even interrupts
-at the same priority as the emulated NMI. In Linux, this should not be the
-case but one should be aware it could happen.
+these slightly differently. The SCI is handled as a high priority interrupt;
+given that these are corrected (or correctable) errors being reported, this
+is sufficient. The NMI is emulated as the highest priority interrupt
+possible. This implies some caution must be used since there could be
+interrupts at higher privilege levels or even interrupts at the same priority
+as the emulated NMI. In Linux, this should not be the case but one should
+be aware it could happen.
ACPI Objects Not Supported on ARM64
-----------------------------------
While this may change in the future, there are several classes of objects
that can be defined, but are not currently of general interest to ARM servers.
+Some of these objects have x86 equivalents, and may actually make sense in ARM
+servers. However, there is either no hardware available at present, or there
+may not even be a non-ARM implementation yet. Hence, they are not currently
+supported.
-These are not supported:
+The following classes of objects are not supported:
-- Section 9.2: ambient light sensor devices
@@ -571,16 +584,6 @@ These are not supported:
-- Section 9.18: time and alarm devices (see 9.15)
-
-ACPI Objects Not Yet Implemented
---------------------------------
-While these objects have x86 equivalents, and they do make some sense in ARM
-servers, there is either no hardware available at present, or in some cases
-there may not yet be a non-ARM implementation. Hence, they are currently not
-implemented though that may change in the future.
-
-Not yet implemented are:
-
-- Section 10: power source and power meter devices
-- Section 11: thermal management
@@ -589,5 +592,31 @@ Not yet implemented are:
-- Section 13: SMBus interfaces
- -- Section 17: NUMA support (prototypes have been submitted for
- review)
+
+This also means that there is no support for the following objects:
+
+Name Section Name Section
+---- ------------ ---- ------------
+_ALC 9.3.4 _FDM 9.10.3
+_ALI 9.3.2 _FIX 6.2.7
+_ALP 9.3.6 _GAI 10.4.5
+_ALR 9.3.5 _GHL 10.4.7
+_ALT 9.3.3 _GTM 9.9.2.1.1
+_BCT 10.2.2.10 _LID 9.5.1
+_BDN 6.5.3 _PAI 10.4.4
+_BIF 10.2.2.1 _PCL 10.3.2
+_BIX 10.2.2.1 _PIF 10.3.3
+_BLT 9.2.3 _PMC 10.4.1
+_BMA 10.2.2.4 _PMD 10.4.8
+_BMC 10.2.2.12 _PMM 10.4.3
+_BMD 10.2.2.11 _PRL 10.3.4
+_BMS 10.2.2.5 _PSR 10.3.1
+_BST 10.2.2.6 _PTP 10.4.2
+_BTH 10.2.2.7 _SBS 10.1.3
+_BTM 10.2.2.9 _SHL 10.4.6
+_BTP 10.2.2.8 _STM 9.9.2.1.1
+_DCK 6.5.2 _UPD 9.16.1
+_EC 12.12 _UPP 9.16.2
+_FDE 9.10.1 _WPC 10.5.2
+_FDI 9.10.2 _WPP 10.5.3
+