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@linaro.org Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will.deacon@arm.com Cc: Jonathan Corbet corbet@lwn.net --- Documentation/arm64/acpi_object_usage.txt | 446 ++++++++++++++++++++++-------- Documentation/arm64/arm-acpi.txt | 28 +- 2 files changed, 357 insertions(+), 117 deletions(-)
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.
On 03/28/2016 06:06 PM, 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@linaro.org Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will.deacon@arm.com Cc: Jonathan Corbet corbet@lwn.net
Documentation/arm64/acpi_object_usage.txt | 446 ++++++++++++++++++++++-------- Documentation/arm64/arm-acpi.txt | 28 +- 2 files changed, 357 insertions(+), 117 deletions(-) [snip...]
Ping? Any further comments or is this good to go?
Thanks.
On Thu, Apr 07, 2016 at 03:50:55PM -0600, Al Stone wrote:
On 03/28/2016 06:06 PM, 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@linaro.org Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will.deacon@arm.com Cc: Jonathan Corbet corbet@lwn.net
Documentation/arm64/acpi_object_usage.txt | 446 ++++++++++++++++++++++-------- Documentation/arm64/arm-acpi.txt | 28 +- 2 files changed, 357 insertions(+), 117 deletions(-) [snip...]
Ping? Any further comments or is this good to go?
It would be nice to see an ack from some other ACPI people, if that's possible. Which tree were you planning to merge this through?
Will
On 04/08/2016 07:12 AM, Will Deacon wrote:
On Thu, Apr 07, 2016 at 03:50:55PM -0600, Al Stone wrote:
On 03/28/2016 06:06 PM, 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@linaro.org Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will.deacon@arm.com Cc: Jonathan Corbet corbet@lwn.net
Documentation/arm64/acpi_object_usage.txt | 446 ++++++++++++++++++++++-------- Documentation/arm64/arm-acpi.txt | 28 +- 2 files changed, 357 insertions(+), 117 deletions(-) [snip...]
Ping? Any further comments or is this good to go?
It would be nice to see an ack from some other ACPI people, if that's possible. Which tree were you planning to merge this through?
Will
Agreed. I was hoping the ping would elicit some of that.
I assumed this would go through the arm64 tree since it's pretty specific to the architecture.
On 2016/3/29 8:06, 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@linaro.org
Acked-by: Hanjun Guo hanjun.guo@linaro.org
Thanks for the doc updating! Hanjun
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@linaro.org Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will.deacon@arm.com Cc: Jonathan Corbet corbet@lwn.net
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, WPBTTable 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 insteadof 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 (AERRoot Port), 7 (AER Endpoint), 8 (AER Bridge), or 9 (Generic HardwareError Source). Firmware first error handling is possible if and onlyif Trusted Firmware is being used on arm64.
ARM-specific error sources have been defined; please use those or thePCI types such as type 6 (AER Root Port), 7 (AER Endpoint), or 8 (AERBridge), or use type 9 (Generic Hardware Error Source). Firmware firsterror handling is possible if and only if Trusted Firmware is beingused 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 foruse with ARM and will be recommended in order to support ACPI powermanagement.
x86 only table as of ACPI 5.1; starting with ACPI 6.0, processordescriptions and power states on ARM platforms should use the DSDTand 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 OEMuse. Since these are not meant to be of general use but are limitedto very specific end users, they are not recommended for use and arenot 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 controlpower 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 tohide 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 aboutwhether such devices are cache coherent or not.The _CCA value is inherited by all descendants ofthese devices so it does not need to be repeated.Without _CCA on arm64, the kernel does not know whatto 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, makingit explicit ensures the kernel will set up DMA asit should.
NB: this method provides default cache coherencyattributes; the presence of an SMMU can be used tomodify that, however. For example, a master coulddefault to non-coherent, but be made coherent withthe appropriate SMMU configuration (see Table 17 ofthe 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 usethan _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 onlybe 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 tablethat provides overrides to hide devices in virtualizedenvironments.-_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 forreview)
+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), sections5.2.16 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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On 04/15/2016 08:37 AM, Lorenzo Pieralisi wrote:
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@linaro.org Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will.deacon@arm.com Cc: Jonathan Corbet corbet@lwn.net
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) ?
The original intent was to provide guidance to those unfamiliar with ACPI, and in particular provide some details on what usage makes sense on ARM. In writing it, the objective was that arm-acpi.txt be primarily an overall view, but that acpi_object_usage.txt answered specific questions about specific objects, which we got asked about frequently since APCI was very new on ARM at the time. That being said, however, it is possible that acpi_object_usage.txt has outlived its usefulness, as those that need to have become familiar with ACPI.
It doesn't help in the ACPI specs since the idea was to try to document recommended Linux-specific usage, which may or may not be OS-agnostic, but would at least be in the open to encourage common usage.
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 (?)) ?
Well, maintenance will be necessary as new spec revisions come out, just like any other part of the kernel code. I don't see anything unique about these documents versus any other; is there something else in the question that I'm not seeing?
I guess I just assumed that since I wrote these, I'd be responsible for keeping them up to date. If you're volunteering to do so, I would not object :-).
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 [snip...]
Does that help clarify?
On Fri, Apr 15, 2016 at 10:41:02AM -0600, Al Stone wrote:
On 04/15/2016 08:37 AM, Lorenzo Pieralisi wrote:
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@linaro.org Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will.deacon@arm.com Cc: Jonathan Corbet corbet@lwn.net
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) ?
The original intent was to provide guidance to those unfamiliar with ACPI, and in particular provide some details on what usage makes sense on ARM. In writing it, the objective was that arm-acpi.txt be primarily an overall view, but that acpi_object_usage.txt answered specific questions about specific objects, which we got asked about frequently since APCI was very new on ARM at the time. That being said, however, it is possible that acpi_object_usage.txt has outlived its usefulness, as those that need to have become familiar with ACPI.
It doesn't help in the ACPI specs since the idea was to try to document recommended Linux-specific usage, which may or may not be OS-agnostic, but would at least be in the open to encourage common usage.
Understood, the point I wanted to make is that adding a list of methods in acpi_object_usage.txt ("Use as needed") is not necessarily additional information, you can add a pointer at ACPI specs (for that specific purpose - as I said there are parts of the patch that add additional information Linux related) for that purpose instead of having to list all of them in acpi_object_usage.txt again.
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 (?)) ?
Well, maintenance will be necessary as new spec revisions come out, just like any other part of the kernel code. I don't see anything unique about these documents versus any other; is there something else in the question that I'm not seeing?
No, see above.
I guess I just assumed that since I wrote these, I'd be responsible for keeping them up to date. If you're volunteering to do so, I would not object :-).
I asked because it is kernel documentation and it has to be reviewed as such, some updates I found them necessary, adding a list of new ACPI methods that came up with ACPI 6.1, maybe, but that's already in the specs, so I question why they should be listed in that file, unless there is something kernel people really have to know, I will comment on the specific methods.
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 [snip...]
Does that help clarify?
Yes, I will send my few minor remarks next week and ACK accordingly, it was just for me to understand, as I mentioned.
Thanks, Lorenzo
On 04/15/2016 11:47 AM, Lorenzo Pieralisi wrote:
On Fri, Apr 15, 2016 at 10:41:02AM -0600, Al Stone wrote:
On 04/15/2016 08:37 AM, Lorenzo Pieralisi wrote:
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@linaro.org Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will.deacon@arm.com Cc: Jonathan Corbet corbet@lwn.net
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) ?
The original intent was to provide guidance to those unfamiliar with ACPI, and in particular provide some details on what usage makes sense on ARM. In writing it, the objective was that arm-acpi.txt be primarily an overall view, but that acpi_object_usage.txt answered specific questions about specific objects, which we got asked about frequently since APCI was very new on ARM at the time. That being said, however, it is possible that acpi_object_usage.txt has outlived its usefulness, as those that need to have become familiar with ACPI.
It doesn't help in the ACPI specs since the idea was to try to document recommended Linux-specific usage, which may or may not be OS-agnostic, but would at least be in the open to encourage common usage.
Understood, the point I wanted to make is that adding a list of methods in acpi_object_usage.txt ("Use as needed") is not necessarily additional information, you can add a pointer at ACPI specs (for that specific purpose - as I said there are parts of the patch that add additional information Linux related) for that purpose instead of having to list all of them in acpi_object_usage.txt again.
I see. That makes sense. How about I collapse those down with something on the order of "unless otherwise noted, use as needed" and just remove the ones that have no specific info?
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 (?)) ?
Well, maintenance will be necessary as new spec revisions come out, just like any other part of the kernel code. I don't see anything unique about these documents versus any other; is there something else in the question that I'm not seeing?
No, see above.
I guess I just assumed that since I wrote these, I'd be responsible for keeping them up to date. If you're volunteering to do so, I would not object :-).
I asked because it is kernel documentation and it has to be reviewed as such, some updates I found them necessary, adding a list of new ACPI methods that came up with ACPI 6.1, maybe, but that's already in the specs, so I question why they should be listed in that file, unless there is something kernel people really have to know, I will comment on the specific methods.
Yup, good point; I can remove the fluff.
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 [snip...]
Does that help clarify?
Yes, I will send my few minor remarks next week and ACK accordingly, it was just for me to understand, as I mentioned.
Thanks. I'll make the changes above, and incorporate your remarks, then send out a new version and you can ACK that if you wish. I really appreciate all the feedback -- thanks for taking the time.
On Fri, Apr 15, 2016 at 11:54:08AM -0600, Al Stone wrote:
[...]
Understood, the point I wanted to make is that adding a list of methods in acpi_object_usage.txt ("Use as needed") is not necessarily additional information, you can add a pointer at ACPI specs (for that specific purpose - as I said there are parts of the patch that add additional information Linux related) for that purpose instead of having to list all of them in acpi_object_usage.txt again.
I see. That makes sense. How about I collapse those down with something on the order of "unless otherwise noted, use as needed" and just remove the ones that have no specific info?
Agreed, that would also help you avoid keeping track of new specs updates that do not necessarily require updates to these docs.
Lorenzo
On Mon, 28 Mar 2016 18:06:42 -0600 Al Stone al.stone@linaro.org wrote:
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.
So I'll happily pull this into the docs tree if that seems like the right place for it. I'd really like to see an ack or two first, though, since I'm not really in a position to review it properly myself.
Thanks,
jon
On 04/15/2016 03:35 PM, Jonathan Corbet wrote:
On Mon, 28 Mar 2016 18:06:42 -0600 Al Stone al.stone@linaro.org wrote:
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.
So I'll happily pull this into the docs tree if that seems like the right place for it. I'd really like to see an ack or two first, though, since I'm not really in a position to review it properly myself.
Thanks,
jon
Agreed; I'd like to see an ACK or two or three first. Thanks for the offer. Stay tuned, I reckon :).
On 3/28/16 5:06 PM, Al Stone wrote:
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
Nit: IORT will only be required on certain SBSA platforms using e.g. GICv3-ITS and an SMMU. On e.g. level 0 platforms, it remains optional.
Sorry for late comment - just catching up on this thread.
Jon.
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