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Diffstat (limited to 'Documentation/admin-guide/acpi')
| -rw-r--r-- | Documentation/admin-guide/acpi/cppc_sysfs.rst | 76 | ||||
| -rw-r--r-- | Documentation/admin-guide/acpi/dsdt-override.rst | 13 | ||||
| -rw-r--r-- | Documentation/admin-guide/acpi/index.rst | 14 | ||||
| -rw-r--r-- | Documentation/admin-guide/acpi/initrd_table_override.rst | 115 | ||||
| -rw-r--r-- | Documentation/admin-guide/acpi/ssdt-overlays.rst | 180 |
5 files changed, 398 insertions, 0 deletions
diff --git a/Documentation/admin-guide/acpi/cppc_sysfs.rst b/Documentation/admin-guide/acpi/cppc_sysfs.rst new file mode 100644 index 000000000000..a4b99afbe331 --- /dev/null +++ b/Documentation/admin-guide/acpi/cppc_sysfs.rst @@ -0,0 +1,76 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================================================== +Collaborative Processor Performance Control (CPPC) +================================================== + +CPPC +==== + +CPPC defined in the ACPI spec describes a mechanism for the OS to manage the +performance of a logical processor on a contigious and abstract performance +scale. CPPC exposes a set of registers to describe abstract performance scale, +to request performance levels and to measure per-cpu delivered performance. + +For more details on CPPC please refer to the ACPI specification at: + +http://uefi.org/specifications + +Some of the CPPC registers are exposed via sysfs under:: + + /sys/devices/system/cpu/cpuX/acpi_cppc/ + +for each cpu X:: + + $ ls -lR /sys/devices/system/cpu/cpu0/acpi_cppc/ + /sys/devices/system/cpu/cpu0/acpi_cppc/: + total 0 + -r--r--r-- 1 root root 65536 Mar 5 19:38 feedback_ctrs + -r--r--r-- 1 root root 65536 Mar 5 19:38 highest_perf + -r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_freq + -r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_nonlinear_perf + -r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_perf + -r--r--r-- 1 root root 65536 Mar 5 19:38 nominal_freq + -r--r--r-- 1 root root 65536 Mar 5 19:38 nominal_perf + -r--r--r-- 1 root root 65536 Mar 5 19:38 reference_perf + -r--r--r-- 1 root root 65536 Mar 5 19:38 wraparound_time + +* highest_perf : Highest performance of this processor (abstract scale). +* nominal_perf : Highest sustained performance of this processor + (abstract scale). +* lowest_nonlinear_perf : Lowest performance of this processor with nonlinear + power savings (abstract scale). +* lowest_perf : Lowest performance of this processor (abstract scale). + +* lowest_freq : CPU frequency corresponding to lowest_perf (in MHz). +* nominal_freq : CPU frequency corresponding to nominal_perf (in MHz). + The above frequencies should only be used to report processor performance in + freqency instead of abstract scale. These values should not be used for any + functional decisions. + +* feedback_ctrs : Includes both Reference and delivered performance counter. + Reference counter ticks up proportional to processor's reference performance. + Delivered counter ticks up proportional to processor's delivered performance. +* wraparound_time: Minimum time for the feedback counters to wraparound + (seconds). +* reference_perf : Performance level at which reference performance counter + accumulates (abstract scale). + + +Computing Average Delivered Performance +======================================= + +Below describes the steps to compute the average performance delivered by +taking two different snapshots of feedback counters at time T1 and T2. + + T1: Read feedback_ctrs as fbc_t1 + Wait or run some workload + + T2: Read feedback_ctrs as fbc_t2 + +:: + + delivered_counter_delta = fbc_t2[del] - fbc_t1[del] + reference_counter_delta = fbc_t2[ref] - fbc_t1[ref] + + delivered_perf = (refernce_perf x delivered_counter_delta) / reference_counter_delta diff --git a/Documentation/admin-guide/acpi/dsdt-override.rst b/Documentation/admin-guide/acpi/dsdt-override.rst new file mode 100644 index 000000000000..50bd7f194bf4 --- /dev/null +++ b/Documentation/admin-guide/acpi/dsdt-override.rst @@ -0,0 +1,13 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============== +Overriding DSDT +=============== + +Linux supports a method of overriding the BIOS DSDT: + +CONFIG_ACPI_CUSTOM_DSDT - builds the image into the kernel. + +When to use this method is described in detail on the +Linux/ACPI home page: +https://01.org/linux-acpi/documentation/overriding-dsdt diff --git a/Documentation/admin-guide/acpi/index.rst b/Documentation/admin-guide/acpi/index.rst new file mode 100644 index 000000000000..4d13eeea1eca --- /dev/null +++ b/Documentation/admin-guide/acpi/index.rst @@ -0,0 +1,14 @@ +============ +ACPI Support +============ + +Here we document in detail how to interact with various mechanisms in +the Linux ACPI support. + +.. toctree:: + :maxdepth: 1 + + initrd_table_override + dsdt-override + ssdt-overlays + cppc_sysfs diff --git a/Documentation/admin-guide/acpi/initrd_table_override.rst b/Documentation/admin-guide/acpi/initrd_table_override.rst new file mode 100644 index 000000000000..cbd768207631 --- /dev/null +++ b/Documentation/admin-guide/acpi/initrd_table_override.rst @@ -0,0 +1,115 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================================ +Upgrading ACPI tables via initrd +================================ + +What is this about +================== + +If the ACPI_TABLE_UPGRADE compile option is true, it is possible to +upgrade the ACPI execution environment that is defined by the ACPI tables +via upgrading the ACPI tables provided by the BIOS with an instrumented, +modified, more recent version one, or installing brand new ACPI tables. + +When building initrd with kernel in a single image, option +ACPI_TABLE_OVERRIDE_VIA_BUILTIN_INITRD should also be true for this +feature to work. + +For a full list of ACPI tables that can be upgraded/installed, take a look +at the char `*table_sigs[MAX_ACPI_SIGNATURE];` definition in +drivers/acpi/tables.c. + +All ACPI tables iasl (Intel's ACPI compiler and disassembler) knows should +be overridable, except: + + - ACPI_SIG_RSDP (has a signature of 6 bytes) + - ACPI_SIG_FACS (does not have an ordinary ACPI table header) + +Both could get implemented as well. + + +What is this for +================ + +Complain to your platform/BIOS vendor if you find a bug which is so severe +that a workaround is not accepted in the Linux kernel. And this facility +allows you to upgrade the buggy tables before your platform/BIOS vendor +releases an upgraded BIOS binary. + +This facility can be used by platform/BIOS vendors to provide a Linux +compatible environment without modifying the underlying platform firmware. + +This facility also provides a powerful feature to easily debug and test +ACPI BIOS table compatibility with the Linux kernel by modifying old +platform provided ACPI tables or inserting new ACPI tables. + +It can and should be enabled in any kernel because there is no functional +change with not instrumented initrds. + + +How does it work +================ +:: + + # Extract the machine's ACPI tables: + cd /tmp + acpidump >acpidump + acpixtract -a acpidump + # Disassemble, modify and recompile them: + iasl -d *.dat + # For example add this statement into a _PRT (PCI Routing Table) function + # of the DSDT: + Store("HELLO WORLD", debug) + # And increase the OEM Revision. For example, before modification: + DefinitionBlock ("DSDT.aml", "DSDT", 2, "INTEL ", "TEMPLATE", 0x00000000) + # After modification: + DefinitionBlock ("DSDT.aml", "DSDT", 2, "INTEL ", "TEMPLATE", 0x00000001) + iasl -sa dsdt.dsl + # Add the raw ACPI tables to an uncompressed cpio archive. + # They must be put into a /kernel/firmware/acpi directory inside the cpio + # archive. Note that if the table put here matches a platform table + # (similar Table Signature, and similar OEMID, and similar OEM Table ID) + # with a more recent OEM Revision, the platform table will be upgraded by + # this table. If the table put here doesn't match a platform table + # (dissimilar Table Signature, or dissimilar OEMID, or dissimilar OEM Table + # ID), this table will be appended. + mkdir -p kernel/firmware/acpi + cp dsdt.aml kernel/firmware/acpi + # A maximum of "NR_ACPI_INITRD_TABLES (64)" tables are currently allowed + # (see osl.c): + iasl -sa facp.dsl + iasl -sa ssdt1.dsl + cp facp.aml kernel/firmware/acpi + cp ssdt1.aml kernel/firmware/acpi + # The uncompressed cpio archive must be the first. Other, typically + # compressed cpio archives, must be concatenated on top of the uncompressed + # one. Following command creates the uncompressed cpio archive and + # concatenates the original initrd on top: + find kernel | cpio -H newc --create > /boot/instrumented_initrd + cat /boot/initrd >>/boot/instrumented_initrd + # reboot with increased acpi debug level, e.g. boot params: + acpi.debug_level=0x2 acpi.debug_layer=0xFFFFFFFF + # and check your syslog: + [ 1.268089] ACPI: PCI Interrupt Routing Table [\_SB_.PCI0._PRT] + [ 1.272091] [ACPI Debug] String [0x0B] "HELLO WORLD" + +iasl is able to disassemble and recompile quite a lot different, +also static ACPI tables. + + +Where to retrieve userspace tools +================================= + +iasl and acpixtract are part of Intel's ACPICA project: +http://acpica.org/ + +and should be packaged by distributions (for example in the acpica package +on SUSE). + +acpidump can be found in Len Browns pmtools: +ftp://kernel.org/pub/linux/kernel/people/lenb/acpi/utils/pmtools/acpidump + +This tool is also part of the acpica package on SUSE. +Alternatively, used ACPI tables can be retrieved via sysfs in latest kernels: +/sys/firmware/acpi/tables diff --git a/Documentation/admin-guide/acpi/ssdt-overlays.rst b/Documentation/admin-guide/acpi/ssdt-overlays.rst new file mode 100644 index 000000000000..da37455f96c9 --- /dev/null +++ b/Documentation/admin-guide/acpi/ssdt-overlays.rst @@ -0,0 +1,180 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============= +SSDT Overlays +============= + +In order to support ACPI open-ended hardware configurations (e.g. development +boards) we need a way to augment the ACPI configuration provided by the firmware +image. A common example is connecting sensors on I2C / SPI buses on development +boards. + +Although this can be accomplished by creating a kernel platform driver or +recompiling the firmware image with updated ACPI tables, neither is practical: +the former proliferates board specific kernel code while the latter requires +access to firmware tools which are often not publicly available. + +Because ACPI supports external references in AML code a more practical +way to augment firmware ACPI configuration is by dynamically loading +user defined SSDT tables that contain the board specific information. + +For example, to enumerate a Bosch BMA222E accelerometer on the I2C bus of the +Minnowboard MAX development board exposed via the LSE connector [1], the +following ASL code can be used:: + + DefinitionBlock ("minnowmax.aml", "SSDT", 1, "Vendor", "Accel", 0x00000003) + { + External (\_SB.I2C6, DeviceObj) + + Scope (\_SB.I2C6) + { + Device (STAC) + { + Name (_ADR, Zero) + Name (_HID, "BMA222E") + + Method (_CRS, 0, Serialized) + { + Name (RBUF, ResourceTemplate () + { + I2cSerialBus (0x0018, ControllerInitiated, 0x00061A80, + AddressingMode7Bit, "\\_SB.I2C6", 0x00, + ResourceConsumer, ,) + GpioInt (Edge, ActiveHigh, Exclusive, PullDown, 0x0000, + "\\_SB.GPO2", 0x00, ResourceConsumer, , ) + { // Pin list + 0 + } + }) + Return (RBUF) + } + } + } + } + +which can then be compiled to AML binary format:: + + $ iasl minnowmax.asl + + Intel ACPI Component Architecture + ASL Optimizing Compiler version 20140214-64 [Mar 29 2014] + Copyright (c) 2000 - 2014 Intel Corporation + + ASL Input: minnomax.asl - 30 lines, 614 bytes, 7 keywords + AML Output: minnowmax.aml - 165 bytes, 6 named objects, 1 executable opcodes + +[1] http://wiki.minnowboard.org/MinnowBoard_MAX#Low_Speed_Expansion_Connector_.28Top.29 + +The resulting AML code can then be loaded by the kernel using one of the methods +below. + +Loading ACPI SSDTs from initrd +============================== + +This option allows loading of user defined SSDTs from initrd and it is useful +when the system does not support EFI or when there is not enough EFI storage. + +It works in a similar way with initrd based ACPI tables override/upgrade: SSDT +aml code must be placed in the first, uncompressed, initrd under the +"kernel/firmware/acpi" path. Multiple files can be used and this will translate +in loading multiple tables. Only SSDT and OEM tables are allowed. See +initrd_table_override.txt for more details. + +Here is an example:: + + # Add the raw ACPI tables to an uncompressed cpio archive. + # They must be put into a /kernel/firmware/acpi directory inside the + # cpio archive. + # The uncompressed cpio archive must be the first. + # Other, typically compressed cpio archives, must be + # concatenated on top of the uncompressed one. + mkdir -p kernel/firmware/acpi + cp ssdt.aml kernel/firmware/acpi + + # Create the uncompressed cpio archive and concatenate the original initrd + # on top: + find kernel | cpio -H newc --create > /boot/instrumented_initrd + cat /boot/initrd >>/boot/instrumented_initrd + +Loading ACPI SSDTs from EFI variables +===================================== + +This is the preferred method, when EFI is supported on the platform, because it +allows a persistent, OS independent way of storing the user defined SSDTs. There +is also work underway to implement EFI support for loading user defined SSDTs +and using this method will make it easier to convert to the EFI loading +mechanism when that will arrive. + +In order to load SSDTs from an EFI variable the efivar_ssdt kernel command line +parameter can be used. The argument for the option is the variable name to +use. If there are multiple variables with the same name but with different +vendor GUIDs, all of them will be loaded. + +In order to store the AML code in an EFI variable the efivarfs filesystem can be +used. It is enabled and mounted by default in /sys/firmware/efi/efivars in all +recent distribution. + +Creating a new file in /sys/firmware/efi/efivars will automatically create a new +EFI variable. Updating a file in /sys/firmware/efi/efivars will update the EFI +variable. Please note that the file name needs to be specially formatted as +"Name-GUID" and that the first 4 bytes in the file (little-endian format) +represent the attributes of the EFI variable (see EFI_VARIABLE_MASK in +include/linux/efi.h). Writing to the file must also be done with one write +operation. + +For example, you can use the following bash script to create/update an EFI +variable with the content from a given file:: + + #!/bin/sh -e + + while ! [ -z "$1" ]; do + case "$1" in + "-f") filename="$2"; shift;; + "-g") guid="$2"; shift;; + *) name="$1";; + esac + shift + done + + usage() + { + echo "Syntax: ${0##*/} -f filename [ -g guid ] name" + exit 1 + } + + [ -n "$name" -a -f "$filename" ] || usage + + EFIVARFS="/sys/firmware/efi/efivars" + + [ -d "$EFIVARFS" ] || exit 2 + + if stat -tf $EFIVARFS | grep -q -v de5e81e4; then + mount -t efivarfs none $EFIVARFS + fi + + # try to pick up an existing GUID + [ -n "$guid" ] || guid=$(find "$EFIVARFS" -name "$name-*" | head -n1 | cut -f2- -d-) + + # use a randomly generated GUID + [ -n "$guid" ] || guid="$(cat /proc/sys/kernel/random/uuid)" + + # efivarfs expects all of the data in one write + tmp=$(mktemp) + /bin/echo -ne "\007\000\000\000" | cat - $filename > $tmp + dd if=$tmp of="$EFIVARFS/$name-$guid" bs=$(stat -c %s $tmp) + rm $tmp + +Loading ACPI SSDTs from configfs +================================ + +This option allows loading of user defined SSDTs from userspace via the configfs +interface. The CONFIG_ACPI_CONFIGFS option must be select and configfs must be +mounted. In the following examples, we assume that configfs has been mounted in +/config. + +New tables can be loading by creating new directories in /config/acpi/table/ and +writing the SSDT aml code in the aml attribute:: + + cd /config/acpi/table + mkdir my_ssdt + cat ~/ssdt.aml > my_ssdt/aml |