Re: [PATCH v3] ARM64: ACPI: Update documentation for latest specification version

From: Lorenzo Pieralisi
Date: Fri Apr 15 2016 - 10:34:42 EST

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Hi Al,

On Mon, Mar 28, 2016 at 06:06:42PM -0600, Al Stone wrote:
> The ACPI 6.1 specification was recently released at the end of January
> 2016, but the arm64 kernel documentation for the use of ACPI was written
> for the 5.1 version of the spec. There were significant additions to the
> spec that had not yet been mentioned -- for example, the 6.0 mechanisms
> added to make it easier to define processors and low power idle states,
> as well as the 6.1 addition allowing regular interrupts (not just from
> GPIO) be used to signal ACPI general purpose events.
>
> This patch reflects going back through and examining the specs in detail
> and updating content appropriately. Whilst there, a few odds and ends of
> typos were caught as well. This brings the documentation up to date with
> ACPI 6.1 for arm64.
>
> Changes for v3:
> -- Clarify use of _LPI/_RDI (Vikas Sajjan)
> -- Whitespace cleanup as pointed out by checkpatch
>
> Changes for v2:
> -- Clean up white space (Harb Abdulhahmid)
> -- Clarification on _CCA usage (Harb Abdulhamid)
> -- IORT moved to required from recommended (Hanjun Guo)
> -- Clarify IORT description (Hanjun Guo)
>
> Signed-off-by: Al Stone <al.stone@xxxxxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Will Deacon <will.deacon@xxxxxxx>
> Cc: Jonathan Corbet <corbet@xxxxxxx>
> ---
> Documentation/arm64/acpi_object_usage.txt | 446 ++++++++++++++++++++++--------
> Documentation/arm64/arm-acpi.txt | 28 +-
> 2 files changed, 357 insertions(+), 117 deletions(-)

I went through this patch twice and before posting my review comments
I have some questions to _ASK ;-):

- Do we really need acpi_object_usage.txt to list all possible ACPI
methods in the ACPI specs ("Use as needed") and update them as the
specs evolve ?
IMO that's what the ACPI specs are for and that's what AML developers
will refer to, I do not see the point in listing all methods in that
file (can't it become an ARM addendum to the ACPI specs at least to
deprecate methods/tables that are obsolete in ARM's world) ?

- How do we keep acpi_object_usage.txt in sync with ACPI specs from now
onwards ? Is that what we really want/need ?

- How do we keep arm-acpi.txt in sync with kernel supported ARM64 ACPI
features (if - given that this document is part of the Linux kernel docs -
its aim is to describe what bits of ACPI are supported on arm64 (?)) ?

So, agreed with fixing the typos, agreed with arm-acpi.txt (and with
updating it) which describes how the ARM64 kernel is using ACPI
methods/tables, but acpi_object_usage.txt and in particular describing
in there what methods are _useful_ and what are not, honestly I think we
should ask ourselves what that file is really meant to be.

Happy to send my review comments as a follow-up since overall the patch
is OK, I wanted to ask the basic questions above first.

Thanks,
Lorenzo

>
> diff --git a/Documentation/arm64/acpi_object_usage.txt b/Documentation/arm64/acpi_object_usage.txt
> index a6e1a18..756d2f8 100644
> --- a/Documentation/arm64/acpi_object_usage.txt
> +++ b/Documentation/arm64/acpi_object_usage.txt
> @@ -11,15 +11,16 @@ outside of the UEFI Forum (see Section 5.2.6 of the specification).
>
> For ACPI on arm64, tables also fall into the following categories:
>
> - -- Required: DSDT, FADT, GTDT, MADT, MCFG, RSDP, SPCR, XSDT
> + -- Required: DSDT, FADT, GTDT, IORT, 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
> + -- Optional: BGRT, CPEP, CSRT, DBG2, DRTM, ECDT, FACS, FPDT, MCHI,
> + MPST, MSCT, NFIT, PMTT, RASF, SBST, SLIT, SPMI, SRAT, STAO, TCPA,
> + TPM2, UEFI, XENV
>
> - -- Not supported: BOOT, DBG2, DBGP, DMAR, ETDT, HPET, IBFT, IVRS,
> - LPIT, MSDM, RSDT, SLIC, WAET, WDAT, WDRT, WPBT
> + -- 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 +51,8 @@ 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 +135,11 @@ 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 +152,27 @@ 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.
> +
> 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 +186,38 @@ 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, and required when using CPPC to control
> + power on the platform.
> +
> +PMTT Section 5.2.21.12 (signature == "PMTT")
> + == Platform Memory Topology Table ==
> + Optional, but useful, but 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 +229,7 @@ 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 ==
> @@ -207,7 +241,7 @@ SLIC Signature Reserved (signature == "SLIC")
>
> SLIT Section 5.2.17 (signature == "SLIT")
> == System Locality distance Information Table ==
> - Optional in general, but required for NUMA systems.
> + Optional in general, but required for arm64 NUMA systems.
>
> SPCR Signature Reserved (signature == "SPCR")
> == Serial Port Console Redirection table ==
> @@ -220,7 +254,7 @@ 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 +269,11 @@ 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 +305,10 @@ 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.
> @@ -273,31 +316,57 @@ 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:
>
> Name Section Usage for ARMv8 Linux
> ---- ------------ -------------------------------------------------
> +_ACx 11.4.1 Use as needed.
> +
> _ADR 6.1.1 Use as needed.
>
> +_ALx 11.4.2 Use as needed.
> +
> +_ART 11.4.3 Use as needed.
> +
> _BBN 6.5.5 Use as needed; PCI-specific.
>
> -_BDN 6.5.3 Optional; not likely to be used on arm64.
> +_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.
>
> -_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.
> + 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).
>
> -_CDM 6.2.1 Optional, to be used only for processor devices.
> +_CDM 6.2.1 Use as needed, to be used only for processor devices.
>
> -_CID 6.1.2 Use as needed.
> +_CID 6.1.2 Use as needed, see also _HID.
>
> -_CLS 6.1.3 Use as needed.
> +_CLS 6.1.3 Use as needed, see also _HID.
> +
> +_CPC 8.4.7.1 Use as needed; power management specific. CPPC is
> + recommended on arm64.
> +
> +_CR3 11.4.5 Use as needed.
>
> _CRS 6.2.2 Required on arm64.
>
> -_DCK 6.5.2 Optional; not likely to be used on arm64.
> +_CRT 11.4.4 Use as needed.
> +
> +_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.
> +
> +_CWS 9.18.6 Use as needed.
>
> _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
> @@ -305,11 +374,11 @@ _DDN 6.1.4 This field can be used for a device name. However,
>
> _DEP 6.5.8 Use as needed.
>
> -_DIS 6.2.3 Optional, for power management use.
> +_DIS 6.2.3 Use as needed, for power management use.
>
> -_DLM 5.7.5 Optional.
> +_DLM 5.7.5 Use as needed.
>
> -_DMA 6.2.4 Optional.
> +_DMA 6.2.4 Use as needed.
>
> _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
> @@ -325,19 +394,29 @@ _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.
> +_DSW 7.3.1 Use as needed; power management specific.
>
> -_EDL 6.3.1 Optional.
> +_DTI 11.4.6 Use as needed.
>
> -_EJD 6.3.2 Optional.
> +_EDL 6.3.1 Use as needed.
>
> -_EJx 6.3.3 Optional.
> +_EJD 6.3.2 Use as needed.
>
> -_FIX 6.2.7 x86 specific, not used on arm64.
> +_EJx 6.3.3 Use as needed.
> +
> +_FIF 11.3.1.1 Use as needed.
> +
> +_FPS 11.3.1.2 Use as needed.
> +
> +_FSL 11.3.1.3 Use as needed.
> +
> +_FST 11.3.1.4 Use as needed.
> +
> +_GCP 9.18.2 Use as needed.
>
> \_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 +428,57 @@ _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.
> +_GRT 9.18.3 Use as needed.
> +
> +_GSB 6.2.7 Use as needed.
> +
> +_GTF 9.9.1.1 Use as needed.
> +
> +_GWS 9.18.5 Use as needed.
>
> _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.
> +_HOT 11.4.7 Use as needed.
> +
> +_HPP 6.2.8 Use as needed, PCI specific.
>
> -_HPX 6.2.9 Optional, PCI specific.
> +_HPX 6.2.9 Use as needed, 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.
> +_HRV 6.1.6 Use as needed, use as needed to clarify device
> + behavior; in some cases, this may be easier to use
> + than _DSD.
>
> _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.
> +_IRC 7.3.15 Use as needed; power management specific.
> +
> +_LCK 6.3.4 Use as needed.
> +
> +_LPI 8.4.4.3 Use as needed, but recommended for use with processor
> + definitions (_HID ACPI0010) on arm64. See also _RDI.
>
> -_LCK 6.3.4 Optional.
> +_MAT 6.2.10 Use as needed; see also the MADT.
>
> -_MAT 6.2.10 Optional; see also the MADT.
> +_MBM 9.13.2.1 Use as needed.
>
> -_MLS 6.1.7 Optional, but highly recommended for use in
> +_MLS 6.1.7 Use as needed, but highly recommended for use in
> internationalization.
>
> -_OFF 7.1.2 It is recommended to define this method for any device
> +_MSG 9.2.2 Use as needed.
> +
> +_MSM 9.13.2.2 Use as needed.
> +
> +_MTL 11.4.8 Use as needed.
> +
> +_NTT 11.4.9 Use as needed.
> +
> +_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
> @@ -405,115 +506,220 @@ _OSC 6.2.11 This method can be a global method in ACPI (i.e.,
> being used or what functionality is provided. The
> _OSC method is to be used instead.
>
> -_OST 6.3.5 Optional.
> +_OST 6.3.5 Use as needed.
> +
> +_PCT 8.4.6.1 Use as needed; power management specific.
>
> _PDC 8.4.1 Deprecated, do not use on arm64.
>
> +_PDL 8.4.6.2 Use as needed; power management specific.
> +
> \_PIC 5.8.1 The method should not be used. On arm64, the only
> interrupt model available is GIC.
>
> -_PLD 6.1.8 Optional.
> +_PLD 6.1.8 Use as needed.
> +
> +_PPC 8.4.6.3 Use as needed; power management specific.
> +
> +_PPE 8.4.8 Use as needed.
>
> \_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.
> +_PRE 7.3.12 Use as needed; power management specific.
> +
> +_PRR 7.3.26 Use as needed; power management specific.
> +
> +_PRS 6.2.12 Use as needed.
>
> _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.
> +_PRW 7.3.13 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.
> +_PSC 7.3.6 Use as needed; power management specific.
> +
> +_PSD 8.4.6.5 Use as needed; power management specific.
>
> -_PSE 7.2.7 Use as needed; power management specific.
> +_PSE 7.3.7 Use as needed; power management specific.
>
> -_PSW 7.2.14 Use as needed; power management specific.
> +_PSL 11.4.10 Use as needed.
>
> -_PSx 7.2.2-5 Use as needed; power management specific. If _PS0 is
> +_PSS 8.4.6.2 Use as needed; power management specific.
> +
> +_PSV 11.4.11 Use as needed.
> +
> +_PSW 7.3.14 Use as needed; power management specific.
> +
> +_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.
> +_PTC 8.4.5.1 Use as needed; power management specific.
> +
> +\_PTS 7.4.1 Use as needed; power management specific.
> +
> +_PUR 8.5.1.1 Use as needed.
> +
> +_PXM 6.2.14 Use as needed.
>
> -_PXM 6.2.14 Optional.
> +_RDI 8.4.4.4 Use as needed, but recommended for use with processor
> + definitions (_HID ACPI0010) on arm64. This should only
> + be used in conjunction with _LPI.
>
> _REG 6.5.4 Use as needed.
>
> \_REV 5.7.4 Always returns the latest version of ACPI supported.
>
> -_RMV 6.3.6 Optional.
> +_RMV 6.3.6 Use as needed.
> +
> +_RST 7.3.25 Use as needed; power management specific.
> +
> +_RTV 11.4.12 Use as needed.
>
> \_SB 5.3.1 Required on arm64; all devices must be defined in this
> namespace.
>
> +_SCP 11.4.13 Use as needed.
> +
> +_SDD 9.9.3.3.1 Use as needed.
> +
> _SEG 6.5.6 Use as needed; PCI-specific.
>
> -\_SI 5.3.1, Optional.
> - 9.1
> +\_SI 5.3.1, Use as needed.
> + 9.2
> +
> +_SLI 6.2.15 Use as needed; recommended when SLIT table is in use.
>
> -_SLI 6.2.15 Optional; recommended when SLIT table is in use.
> +_SRT 9.18.4 Use as needed.
>
> _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.
> +
> +_SST 9.2.1 Use as needed.
>
> _STR 6.1.10 Recommended for conveying device names to end users;
> this is preferred over using _DDN.
>
> +_SST 9.2.1 Use as needed.
> +
> +_STP 9.18.7 Use as needed.
> +
> +_STV 9.18.8 Use as needed.
> +
> _SUB 6.1.9 Use as needed; _HID or _CID are preferred.
>
> -_SUN 6.1.11 Optional.
> +_SUN 6.1.11 Use as needed, but recommended.
>
> -\_Sx 7.3.2 Use as needed; power management specific.
> +\_Sx 7.4.2 Use as needed; power management specific.
>
> -_SxD 7.2.16-19 Use as needed; power management specific.
> +_SxD 7.3.16-19 Use as needed; power management specific.
>
> -_SxW 7.2.20-24 Use as needed; power management specific.
> +_SxW 7.3.20-24 Use as needed; power management specific.
>
> -_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.
> +_TC1 11.4.14 Use as needed.
> +
> +_TC2 11.4.15 Use as needed.
> +
> +_TDL 8.4.5.5 Use as needed; power management specific.
> +
> +_TFP 11.4.16 Use as needed.
> +
> +_TIP 9.18.9 Use as needed.
> +
> +_TIV 9.18.10 Use as needed.
> +
> +_TMP 11.4.17 Use as needed.
> +
> +_TPC 8.4.5.3 Use as needed; power management specific.
>
> -\_TZ 5.3.1 Optional.
> +_TPT 11.4.18 Use as needed.
> +
> +_TRT 11.4.19 Use as needed.
> +
> +_TSD 8.4.5.4 Use as needed; power management specific.
> +
> +_TSN 11.4.20 Use as needed.
> +
> +_TSP 11.4.21 Use as needed.
> +
> +_TSS 8.4.5.2 Use as needed; power management specific.
> +
> +_TST 11.4.22 Use as needed.
> +
> +\_TTS 7.4.4 Use as needed; power management specific.
> +
> +\_TZ 5.3.1 Use as needed.
> +
> +_TZD 11.4.23 Use as needed.
> +
> +_TZM 11.4.24 Use as needed.
> +
> +_TZP 11.4.25 Use as needed.
>
> _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.
> +_UPC 9.14 Use as needed.
> +
> +\_WAK 7.4.5 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 sychronization. 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 may be possible using
> +parking protocol, but only PSCI is to be used for ARM servers.
>
>
> ACPI System Address Map Interfaces
> @@ -535,21 +741,25 @@ 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 +781,6 @@ 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 +789,31 @@ Not yet implemented are:
>
> -- Section 13: SMBus interfaces
>
> - -- Section 17: NUMA support (prototypes have been submitted for
> - review)
> +
> +This also mean 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
> +
> diff --git a/Documentation/arm64/arm-acpi.txt b/Documentation/arm64/arm-acpi.txt
> index 570a4f8..12381c1 100644
> --- a/Documentation/arm64/arm-acpi.txt
> +++ b/Documentation/arm64/arm-acpi.txt
> @@ -57,11 +57,11 @@ The short form of the rationale for ACPI on ARM is:
>
> -- The new ACPI governance process works well and Linux is now at the same
> table as hardware vendors and other OS vendors. In fact, there is no
> - longer any reason to feel that ACPI is only belongs to Windows or that
> + longer any reason to feel that ACPI only belongs to Windows or that
> Linux is in any way secondary to Microsoft in this arena. The move of
> ACPI governance into the UEFI forum has significantly opened up the
> specification development process, and currently, a large portion of the
> - changes being made to ACPI is being driven by Linux.
> + changes being made to ACPI are being driven by Linux.
>
> Key to the use of ACPI is the support model. For servers in general, the
> responsibility for hardware behaviour cannot solely be the domain of the
> @@ -159,7 +159,7 @@ Further, the ACPI core will only use the 64-bit address fields in the FADT
> (Fixed ACPI Description Table). Any 32-bit address fields in the FADT will
> be ignored on arm64.
>
> -Hardware reduced mode (see Section 4.1 of the ACPI 5.1 specification) will
> +Hardware reduced mode (see Section 4.1 of the ACPI 6.1 specification) will
> be enforced by the ACPI core on arm64. Doing so allows the ACPI core to
> run less complex code since it no longer has to provide support for legacy
> hardware from other architectures. Any fields that are not to be used for
> @@ -167,7 +167,7 @@ hardware reduced mode must be set to zero.
>
> For the ACPI core to operate properly, and in turn provide the information
> the kernel needs to configure devices, it expects to find the following
> -tables (all section numbers refer to the ACPI 5.1 specfication):
> +tables (all section numbers refer to the ACPI 6.1 specfication):
>
> -- RSDP (Root System Description Pointer), section 5.2.5
>
> @@ -185,9 +185,22 @@ tables (all section numbers refer to the ACPI 5.1 specfication):
> -- If PCI is supported, the MCFG (Memory mapped ConFiGuration
> Table), section 5.2.6, specifically Table 5-31.
>
> + -- If booting without a console=<device> kernel parameter is
> + supported, the SPCR (Serial Port Console Redirection table),
> + section 5.2.6, specifically Table 5-31.
> +
> + -- If virtualization is supported, the IORT (Input Output Remapping
> + Table, section 5.2.6, specifically Table 5-31.
> +
> + -- If NUMA is supported, the SRAT (System Resource Affinity Table)
> + and SLIT (System Locality distance Information Table), sections
> + 5.2.16 and 5.2.17, respectively.
> +
> If the above tables are not all present, the kernel may or may not be
> able to boot properly since it may not be able to configure all of the
> -devices available.
> +devices available. This list of tables is not meant to be all inclusive;
> +in some environments other tables may be needed (e.g., any of the APEI
> +tables from section 18) to support specific functionality.
>
>
> ACPI Detection
> @@ -233,7 +246,7 @@ that looks like this: Name(KEY0, "value0"). An ACPI device driver would
> then retrieve the value of the property by evaluating the KEY0 object.
> However, using Name() this way has multiple problems: (1) ACPI limits
> names ("KEY0") to four characters unlike DT; (2) there is no industry
> -wide registry that maintains a list of names, minimzing re-use; (3)
> +wide registry that maintains a list of names, minimizing re-use; (3)
> there is also no registry for the definition of property values ("value0"),
> again making re-use difficult; and (4) how does one maintain backward
> compatibility as new hardware comes out? The _DSD method was created
> @@ -434,7 +447,8 @@ The ACPI specification changes regularly. During the year 2014, for instance,
> version 5.1 was released and version 6.0 substantially completed, with most of
> the changes being driven by ARM-specific requirements. Proposed changes are
> presented and discussed in the ASWG (ACPI Specification Working Group) which
> -is a part of the UEFI Forum.
> +is a part of the UEFI Forum. The current version of the ACPI specification
> +is 6.1 release in January 2016.
>
> Participation in this group is open to all UEFI members. Please see
> http://www.uefi.org/workinggroup for details on group membership.
> --
> 2.5.5
>
> --
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