diff options
| -rw-r--r-- | Documentation/admin-guide/pm/cpufreq_drivers.rst | 274 | ||||
| -rw-r--r-- | Documentation/admin-guide/pm/working-state.rst | 1 | ||||
| -rw-r--r-- | Documentation/cpu-freq/amd-powernow.txt | 38 | ||||
| -rw-r--r-- | Documentation/cpu-freq/cpufreq-nforce2.txt | 19 | ||||
| -rw-r--r-- | Documentation/cpu-freq/pcc-cpufreq.txt | 207 |
5 files changed, 275 insertions, 264 deletions
diff --git a/Documentation/admin-guide/pm/cpufreq_drivers.rst b/Documentation/admin-guide/pm/cpufreq_drivers.rst new file mode 100644 index 000000000000..9a134ae65803 --- /dev/null +++ b/Documentation/admin-guide/pm/cpufreq_drivers.rst @@ -0,0 +1,274 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================================================= +Legacy Documentation of CPU Performance Scaling Drivers +======================================================= + +Included below are historic documents describing assorted +:doc:`CPU performance scaling <cpufreq>` drivers. They are reproduced verbatim, +with the original white space formatting and indentation preserved, except for +the added leading space character in every line of text. + + +AMD PowerNow! Drivers +===================== + +:: + + PowerNow! and Cool'n'Quiet are AMD names for frequency + management capabilities in AMD processors. As the hardware + implementation changes in new generations of the processors, + there is a different cpu-freq driver for each generation. + + Note that the driver's will not load on the "wrong" hardware, + so it is safe to try each driver in turn when in doubt as to + which is the correct driver. + + Note that the functionality to change frequency (and voltage) + is not available in all processors. The drivers will refuse + to load on processors without this capability. The capability + is detected with the cpuid instruction. + + The drivers use BIOS supplied tables to obtain frequency and + voltage information appropriate for a particular platform. + Frequency transitions will be unavailable if the BIOS does + not supply these tables. + + 6th Generation: powernow-k6 + + 7th Generation: powernow-k7: Athlon, Duron, Geode. + + 8th Generation: powernow-k8: Athlon, Athlon 64, Opteron, Sempron. + Documentation on this functionality in 8th generation processors + is available in the "BIOS and Kernel Developer's Guide", publication + 26094, in chapter 9, available for download from www.amd.com. + + BIOS supplied data, for powernow-k7 and for powernow-k8, may be + from either the PSB table or from ACPI objects. The ACPI support + is only available if the kernel config sets CONFIG_ACPI_PROCESSOR. + The powernow-k8 driver will attempt to use ACPI if so configured, + and fall back to PST if that fails. + The powernow-k7 driver will try to use the PSB support first, and + fall back to ACPI if the PSB support fails. A module parameter, + acpi_force, is provided to force ACPI support to be used instead + of PSB support. + + +``cpufreq-nforce2`` +=================== + +:: + + The cpufreq-nforce2 driver changes the FSB on nVidia nForce2 platforms. + + This works better than on other platforms, because the FSB of the CPU + can be controlled independently from the PCI/AGP clock. + + The module has two options: + + fid: multiplier * 10 (for example 8.5 = 85) + min_fsb: minimum FSB + + If not set, fid is calculated from the current CPU speed and the FSB. + min_fsb defaults to FSB at boot time - 50 MHz. + + IMPORTANT: The available range is limited downwards! + Also the minimum available FSB can differ, for systems + booting with 200 MHz, 150 should always work. + + +``pcc-cpufreq`` +=============== + +:: + + /* + * pcc-cpufreq.txt - PCC interface documentation + * + * Copyright (C) 2009 Red Hat, Matthew Garrett <mjg@redhat.com> + * Copyright (C) 2009 Hewlett-Packard Development Company, L.P. + * Nagananda Chumbalkar <nagananda.chumbalkar@hp.com> + */ + + + Processor Clocking Control Driver + --------------------------------- + + Contents: + --------- + 1. Introduction + 1.1 PCC interface + 1.1.1 Get Average Frequency + 1.1.2 Set Desired Frequency + 1.2 Platforms affected + 2. Driver and /sys details + 2.1 scaling_available_frequencies + 2.2 cpuinfo_transition_latency + 2.3 cpuinfo_cur_freq + 2.4 related_cpus + 3. Caveats + + 1. Introduction: + ---------------- + Processor Clocking Control (PCC) is an interface between the platform + firmware and OSPM. It is a mechanism for coordinating processor + performance (ie: frequency) between the platform firmware and the OS. + + The PCC driver (pcc-cpufreq) allows OSPM to take advantage of the PCC + interface. + + OS utilizes the PCC interface to inform platform firmware what frequency the + OS wants for a logical processor. The platform firmware attempts to achieve + the requested frequency. If the request for the target frequency could not be + satisfied by platform firmware, then it usually means that power budget + conditions are in place, and "power capping" is taking place. + + 1.1 PCC interface: + ------------------ + The complete PCC specification is available here: + https://acpica.org/sites/acpica/files/Processor-Clocking-Control-v1p0.pdf + + PCC relies on a shared memory region that provides a channel for communication + between the OS and platform firmware. PCC also implements a "doorbell" that + is used by the OS to inform the platform firmware that a command has been + sent. + + The ACPI PCCH() method is used to discover the location of the PCC shared + memory region. The shared memory region header contains the "command" and + "status" interface. PCCH() also contains details on how to access the platform + doorbell. + + The following commands are supported by the PCC interface: + * Get Average Frequency + * Set Desired Frequency + + The ACPI PCCP() method is implemented for each logical processor and is + used to discover the offsets for the input and output buffers in the shared + memory region. + + When PCC mode is enabled, the platform will not expose processor performance + or throttle states (_PSS, _TSS and related ACPI objects) to OSPM. Therefore, + the native P-state driver (such as acpi-cpufreq for Intel, powernow-k8 for + AMD) will not load. + + However, OSPM remains in control of policy. The governor (eg: "ondemand") + computes the required performance for each processor based on server workload. + The PCC driver fills in the command interface, and the input buffer and + communicates the request to the platform firmware. The platform firmware is + responsible for delivering the requested performance. + + Each PCC command is "global" in scope and can affect all the logical CPUs in + the system. Therefore, PCC is capable of performing "group" updates. With PCC + the OS is capable of getting/setting the frequency of all the logical CPUs in + the system with a single call to the BIOS. + + 1.1.1 Get Average Frequency: + ---------------------------- + This command is used by the OSPM to query the running frequency of the + processor since the last time this command was completed. The output buffer + indicates the average unhalted frequency of the logical processor expressed as + a percentage of the nominal (ie: maximum) CPU frequency. The output buffer + also signifies if the CPU frequency is limited by a power budget condition. + + 1.1.2 Set Desired Frequency: + ---------------------------- + This command is used by the OSPM to communicate to the platform firmware the + desired frequency for a logical processor. The output buffer is currently + ignored by OSPM. The next invocation of "Get Average Frequency" will inform + OSPM if the desired frequency was achieved or not. + + 1.2 Platforms affected: + ----------------------- + The PCC driver will load on any system where the platform firmware: + * supports the PCC interface, and the associated PCCH() and PCCP() methods + * assumes responsibility for managing the hardware clocking controls in order + to deliver the requested processor performance + + Currently, certain HP ProLiant platforms implement the PCC interface. On those + platforms PCC is the "default" choice. + + However, it is possible to disable this interface via a BIOS setting. In + such an instance, as is also the case on platforms where the PCC interface + is not implemented, the PCC driver will fail to load silently. + + 2. Driver and /sys details: + --------------------------- + When the driver loads, it merely prints the lowest and the highest CPU + frequencies supported by the platform firmware. + + The PCC driver loads with a message such as: + pcc-cpufreq: (v1.00.00) driver loaded with frequency limits: 1600 MHz, 2933 + MHz + + This means that the OPSM can request the CPU to run at any frequency in + between the limits (1600 MHz, and 2933 MHz) specified in the message. + + Internally, there is no need for the driver to convert the "target" frequency + to a corresponding P-state. + + The VERSION number for the driver will be of the format v.xy.ab. + eg: 1.00.02 + ----- -- + | | + | -- this will increase with bug fixes/enhancements to the driver + |-- this is the version of the PCC specification the driver adheres to + + + The following is a brief discussion on some of the fields exported via the + /sys filesystem and how their values are affected by the PCC driver: + + 2.1 scaling_available_frequencies: + ---------------------------------- + scaling_available_frequencies is not created in /sys. No intermediate + frequencies need to be listed because the BIOS will try to achieve any + frequency, within limits, requested by the governor. A frequency does not have + to be strictly associated with a P-state. + + 2.2 cpuinfo_transition_latency: + ------------------------------- + The cpuinfo_transition_latency field is 0. The PCC specification does + not include a field to expose this value currently. + + 2.3 cpuinfo_cur_freq: + --------------------- + A) Often cpuinfo_cur_freq will show a value different than what is declared + in the scaling_available_frequencies or scaling_cur_freq, or scaling_max_freq. + This is due to "turbo boost" available on recent Intel processors. If certain + conditions are met the BIOS can achieve a slightly higher speed than requested + by OSPM. An example: + + scaling_cur_freq : 2933000 + cpuinfo_cur_freq : 3196000 + + B) There is a round-off error associated with the cpuinfo_cur_freq value. + Since the driver obtains the current frequency as a "percentage" (%) of the + nominal frequency from the BIOS, sometimes, the values displayed by + scaling_cur_freq and cpuinfo_cur_freq may not match. An example: + + scaling_cur_freq : 1600000 + cpuinfo_cur_freq : 1583000 + + In this example, the nominal frequency is 2933 MHz. The driver obtains the + current frequency, cpuinfo_cur_freq, as 54% of the nominal frequency: + + 54% of 2933 MHz = 1583 MHz + + Nominal frequency is the maximum frequency of the processor, and it usually + corresponds to the frequency of the P0 P-state. + + 2.4 related_cpus: + ----------------- + The related_cpus field is identical to affected_cpus. + + affected_cpus : 4 + related_cpus : 4 + + Currently, the PCC driver does not evaluate _PSD. The platforms that support + PCC do not implement SW_ALL. So OSPM doesn't need to perform any coordination + to ensure that the same frequency is requested of all dependent CPUs. + + 3. Caveats: + ----------- + The "cpufreq_stats" module in its present form cannot be loaded and + expected to work with the PCC driver. Since the "cpufreq_stats" module + provides information wrt each P-state, it is not applicable to the PCC driver. diff --git a/Documentation/admin-guide/pm/working-state.rst b/Documentation/admin-guide/pm/working-state.rst index 88f717e59a42..0a38cdf39df1 100644 --- a/Documentation/admin-guide/pm/working-state.rst +++ b/Documentation/admin-guide/pm/working-state.rst @@ -11,4 +11,5 @@ Working-State Power Management intel_idle cpufreq intel_pstate + cpufreq_drivers intel_epb diff --git a/Documentation/cpu-freq/amd-powernow.txt b/Documentation/cpu-freq/amd-powernow.txt deleted file mode 100644 index 254da155fa47..000000000000 --- a/Documentation/cpu-freq/amd-powernow.txt +++ /dev/null @@ -1,38 +0,0 @@ - -PowerNow! and Cool'n'Quiet are AMD names for frequency -management capabilities in AMD processors. As the hardware -implementation changes in new generations of the processors, -there is a different cpu-freq driver for each generation. - -Note that the driver's will not load on the "wrong" hardware, -so it is safe to try each driver in turn when in doubt as to -which is the correct driver. - -Note that the functionality to change frequency (and voltage) -is not available in all processors. The drivers will refuse -to load on processors without this capability. The capability -is detected with the cpuid instruction. - -The drivers use BIOS supplied tables to obtain frequency and -voltage information appropriate for a particular platform. -Frequency transitions will be unavailable if the BIOS does -not supply these tables. - -6th Generation: powernow-k6 - -7th Generation: powernow-k7: Athlon, Duron, Geode. - -8th Generation: powernow-k8: Athlon, Athlon 64, Opteron, Sempron. -Documentation on this functionality in 8th generation processors -is available in the "BIOS and Kernel Developer's Guide", publication -26094, in chapter 9, available for download from www.amd.com. - -BIOS supplied data, for powernow-k7 and for powernow-k8, may be -from either the PSB table or from ACPI objects. The ACPI support -is only available if the kernel config sets CONFIG_ACPI_PROCESSOR. -The powernow-k8 driver will attempt to use ACPI if so configured, -and fall back to PST if that fails. -The powernow-k7 driver will try to use the PSB support first, and -fall back to ACPI if the PSB support fails. A module parameter, -acpi_force, is provided to force ACPI support to be used instead -of PSB support. diff --git a/Documentation/cpu-freq/cpufreq-nforce2.txt b/Documentation/cpu-freq/cpufreq-nforce2.txt deleted file mode 100644 index babce1315026..000000000000 --- a/Documentation/cpu-freq/cpufreq-nforce2.txt +++ /dev/null @@ -1,19 +0,0 @@ - -The cpufreq-nforce2 driver changes the FSB on nVidia nForce2 platforms. - -This works better than on other platforms, because the FSB of the CPU -can be controlled independently from the PCI/AGP clock. - -The module has two options: - - fid: multiplier * 10 (for example 8.5 = 85) - min_fsb: minimum FSB - -If not set, fid is calculated from the current CPU speed and the FSB. -min_fsb defaults to FSB at boot time - 50 MHz. - -IMPORTANT: The available range is limited downwards! - Also the minimum available FSB can differ, for systems - booting with 200 MHz, 150 should always work. - - diff --git a/Documentation/cpu-freq/pcc-cpufreq.txt b/Documentation/cpu-freq/pcc-cpufreq.txt deleted file mode 100644 index 9e3c3b33514c..000000000000 --- a/Documentation/cpu-freq/pcc-cpufreq.txt +++ /dev/null @@ -1,207 +0,0 @@ -/* - * pcc-cpufreq.txt - PCC interface documentation - * - * Copyright (C) 2009 Red Hat, Matthew Garrett <mjg@redhat.com> - * Copyright (C) 2009 Hewlett-Packard Development Company, L.P. - * Nagananda Chumbalkar <nagananda.chumbalkar@hp.com> - * - * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; version 2 of the License. - * - * This program is distributed in the hope that it will be useful, but - * WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or NON - * INFRINGEMENT. See the GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License along - * with this program; if not, write to the Free Software Foundation, Inc., - * 675 Mass Ave, Cambridge, MA 02139, USA. - * - * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - */ - - - Processor Clocking Control Driver - --------------------------------- - -Contents: ---------- -1. Introduction -1.1 PCC interface -1.1.1 Get Average Frequency -1.1.2 Set Desired Frequency -1.2 Platforms affected -2. Driver and /sys details -2.1 scaling_available_frequencies -2.2 cpuinfo_transition_latency -2.3 cpuinfo_cur_freq -2.4 related_cpus -3. Caveats - -1. Introduction: ----------------- -Processor Clocking Control (PCC) is an interface between the platform -firmware and OSPM. It is a mechanism for coordinating processor -performance (ie: frequency) between the platform firmware and the OS. - -The PCC driver (pcc-cpufreq) allows OSPM to take advantage of the PCC -interface. - -OS utilizes the PCC interface to inform platform firmware what frequency the -OS wants for a logical processor. The platform firmware attempts to achieve -the requested frequency. If the request for the target frequency could not be -satisfied by platform firmware, then it usually means that power budget -conditions are in place, and "power capping" is taking place. - -1.1 PCC interface: ------------------- -The complete PCC specification is available here: -http://www.acpica.org/download/Processor-Clocking-Control-v1p0.pdf - -PCC relies on a shared memory region that provides a channel for communication -between the OS and platform firmware. PCC also implements a "doorbell" that -is used by the OS to inform the platform firmware that a command has been -sent. - -The ACPI PCCH() method is used to discover the location of the PCC shared -memory region. The shared memory region header contains the "command" and -"status" interface. PCCH() also contains details on how to access the platform -doorbell. - -The following commands are supported by the PCC interface: -* Get Average Frequency -* Set Desired Frequency - -The ACPI PCCP() method is implemented for each logical processor and is -used to discover the offsets for the input and output buffers in the shared -memory region. - -When PCC mode is enabled, the platform will not expose processor performance -or throttle states (_PSS, _TSS and related ACPI objects) to OSPM. Therefore, -the native P-state driver (such as acpi-cpufreq for Intel, powernow-k8 for -AMD) will not load. - -However, OSPM remains in control of policy. The governor (eg: "ondemand") -computes the required performance for each processor based on server workload. -The PCC driver fills in the command interface, and the input buffer and -communicates the request to the platform firmware. The platform firmware is -responsible for delivering the requested performance. - -Each PCC command is "global" in scope and can affect all the logical CPUs in -the system. Therefore, PCC is capable of performing "group" updates. With PCC -the OS is capable of getting/setting the frequency of all the logical CPUs in -the system with a single call to the BIOS. - -1.1.1 Get Average Frequency: ----------------------------- -This command is used by the OSPM to query the running frequency of the -processor since the last time this command was completed. The output buffer -indicates the average unhalted frequency of the logical processor expressed as -a percentage of the nominal (ie: maximum) CPU frequency. The output buffer -also signifies if the CPU frequency is limited by a power budget condition. - -1.1.2 Set Desired Frequency: ----------------------------- -This command is used by the OSPM to communicate to the platform firmware the -desired frequency for a logical processor. The output buffer is currently -ignored by OSPM. The next invocation of "Get Average Frequency" will inform -OSPM if the desired frequency was achieved or not. - -1.2 Platforms affected: ------------------------ -The PCC driver will load on any system where the platform firmware: -* supports the PCC interface, and the associated PCCH() and PCCP() methods -* assumes responsibility for managing the hardware clocking controls in order -to deliver the requested processor performance - -Currently, certain HP ProLiant platforms implement the PCC interface. On those -platforms PCC is the "default" choice. - -However, it is possible to disable this interface via a BIOS setting. In -such an instance, as is also the case on platforms where the PCC interface -is not implemented, the PCC driver will fail to load silently. - -2. Driver and /sys details: ---------------------------- -When the driver loads, it merely prints the lowest and the highest CPU -frequencies supported by the platform firmware. - -The PCC driver loads with a message such as: -pcc-cpufreq: (v1.00.00) driver loaded with frequency limits: 1600 MHz, 2933 -MHz - -This means that the OPSM can request the CPU to run at any frequency in -between the limits (1600 MHz, and 2933 MHz) specified in the message. - -Internally, there is no need for the driver to convert the "target" frequency -to a corresponding P-state. - -The VERSION number for the driver will be of the format v.xy.ab. -eg: 1.00.02 - ----- -- - | | - | -- this will increase with bug fixes/enhancements to the driver - |-- this is the version of the PCC specification the driver adheres to - - -The following is a brief discussion on some of the fields exported via the -/sys filesystem and how their values are affected by the PCC driver: - -2.1 scaling_available_frequencies: ----------------------------------- -scaling_available_frequencies is not created in /sys. No intermediate -frequencies need to be listed because the BIOS will try to achieve any -frequency, within limits, requested by the governor. A frequency does not have -to be strictly associated with a P-state. - -2.2 cpuinfo_transition_latency: -------------------------------- -The cpuinfo_transition_latency field is 0. The PCC specification does -not include a field to expose this value currently. - -2.3 cpuinfo_cur_freq: ---------------------- -A) Often cpuinfo_cur_freq will show a value different than what is declared -in the scaling_available_frequencies or scaling_cur_freq, or scaling_max_freq. -This is due to "turbo boost" available on recent Intel processors. If certain -conditions are met the BIOS can achieve a slightly higher speed than requested -by OSPM. An example: - -scaling_cur_freq : 2933000 -cpuinfo_cur_freq : 3196000 - -B) There is a round-off error associated with the cpuinfo_cur_freq value. -Since the driver obtains the current frequency as a "percentage" (%) of the -nominal frequency from the BIOS, sometimes, the values displayed by -scaling_cur_freq and cpuinfo_cur_freq may not match. An example: - -scaling_cur_freq : 1600000 -cpuinfo_cur_freq : 1583000 - -In this example, the nominal frequency is 2933 MHz. The driver obtains the -current frequency, cpuinfo_cur_freq, as 54% of the nominal frequency: - - 54% of 2933 MHz = 1583 MHz - -Nominal frequency is the maximum frequency of the processor, and it usually -corresponds to the frequency of the P0 P-state. - -2.4 related_cpus: ------------------ -The related_cpus field is identical to affected_cpus. - -affected_cpus : 4 -related_cpus : 4 - -Currently, the PCC driver does not evaluate _PSD. The platforms that support -PCC do not implement SW_ALL. So OSPM doesn't need to perform any coordination -to ensure that the same frequency is requested of all dependent CPUs. - -3. Caveats: ------------ -The "cpufreq_stats" module in its present form cannot be loaded and -expected to work with the PCC driver. Since the "cpufreq_stats" module -provides information wrt each P-state, it is not applicable to the PCC driver. |