From 03b22496502dacb8a4f3b65e08fcde1d606cbff2 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Thu, 27 Feb 2020 23:30:48 +0100 Subject: Documentation: cpufreq: Move legacy driver documentation There are three legacy driver documents in Documentation/cpu-freq/ that were added years ago and converting them each to the .rst format is rather pointless, even though there is some value in preserving them. However, if they are preserved, they need to go into the admin-guide part of cpufreq documentation where they belong (at least to a certain extent). To preserve them with minimum amount of changes and put them into the right place, and make it possible to process them into HTML (and other formats) along with the rest of the documentation, move them each as a "literal text" block into a separate section of a single .rst "wrapper" file under Documentation/admin-guide/pm/. While at it, repair the PCC specification URL in one of them. Signed-off-by: Rafael J. Wysocki --- Documentation/admin-guide/pm/cpufreq_drivers.rst | 274 +++++++++++++++++++++++ Documentation/admin-guide/pm/working-state.rst | 1 + Documentation/cpu-freq/amd-powernow.txt | 38 ---- Documentation/cpu-freq/cpufreq-nforce2.txt | 19 -- Documentation/cpu-freq/pcc-cpufreq.txt | 207 ----------------- 5 files changed, 275 insertions(+), 264 deletions(-) create mode 100644 Documentation/admin-guide/pm/cpufreq_drivers.rst delete mode 100644 Documentation/cpu-freq/amd-powernow.txt delete mode 100644 Documentation/cpu-freq/cpufreq-nforce2.txt delete mode 100644 Documentation/cpu-freq/pcc-cpufreq.txt 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 ` 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 + * Copyright (C) 2009 Hewlett-Packard Development Company, L.P. + * Nagananda Chumbalkar + */ + + + 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 - * Copyright (C) 2009 Hewlett-Packard Development Company, L.P. - * Nagananda Chumbalkar - * - * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - * - * 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. -- cgit v1.2.3 From 27565c9e22ddd158f918456b2712a06b05b4da5e Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Thu, 27 Feb 2020 13:07:21 -0600 Subject: powercap: idle_inject: Replace zero-length array with flexible-array member The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] Lastly, fix the following checkpatch warning: WARNING: Prefer 'unsigned long' over 'unsigned long int' as the int is unnecessary + unsigned long int cpumask[]; This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva Signed-off-by: Rafael J. Wysocki --- drivers/powercap/idle_inject.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/powercap/idle_inject.c b/drivers/powercap/idle_inject.c index cd1270614cc6..e9bbd3c42eef 100644 --- a/drivers/powercap/idle_inject.c +++ b/drivers/powercap/idle_inject.c @@ -67,7 +67,7 @@ struct idle_inject_device { struct hrtimer timer; unsigned int idle_duration_us; unsigned int run_duration_us; - unsigned long int cpumask[0]; + unsigned long cpumask[]; }; static DEFINE_PER_CPU(struct idle_inject_thread, idle_inject_thread); -- cgit v1.2.3 From c3419b71a7ee5df835edb64ec83c92de29430b85 Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Tue, 3 Mar 2020 14:52:02 +0100 Subject: docs: cpufreq: fix a broken reference The old cpufreq docs got moved. Let's also update its pointer inside Kconfig.x86. Fixes: 03b22496502d ("Documentation: cpufreq: Move legacy driver documentation") Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Rafael J. Wysocki --- drivers/cpufreq/Kconfig.x86 | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/cpufreq/Kconfig.x86 b/drivers/cpufreq/Kconfig.x86 index a6528388952e..62502d0e4c33 100644 --- a/drivers/cpufreq/Kconfig.x86 +++ b/drivers/cpufreq/Kconfig.x86 @@ -25,7 +25,7 @@ config X86_PCC_CPUFREQ This driver adds support for the PCC interface. For details, take a look at: - . + . To compile this driver as a module, choose M here: the module will be called pcc-cpufreq. -- cgit v1.2.3 From 12bd112bf8e41ad0a5cbf6d71beacca45eb7d10c Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Tue, 3 Mar 2020 14:52:03 +0100 Subject: docs: cpu-freq: convert index.txt to ReST most of the stuff there can be re-used with ReST format, but we need to add an empty TOC and remove the existing entries, as the following conversion patches will be re-adding them, as they're converted. Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Rafael J. Wysocki --- Documentation/cpu-freq/index.rst | 35 +++++++++++++++++++++++++ Documentation/cpu-freq/index.txt | 56 ---------------------------------------- Documentation/index.rst | 1 + 3 files changed, 36 insertions(+), 56 deletions(-) create mode 100644 Documentation/cpu-freq/index.rst delete mode 100644 Documentation/cpu-freq/index.txt diff --git a/Documentation/cpu-freq/index.rst b/Documentation/cpu-freq/index.rst new file mode 100644 index 000000000000..1bff3dfddd23 --- /dev/null +++ b/Documentation/cpu-freq/index.rst @@ -0,0 +1,35 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================================================================== +Linux CPUFreq - CPU frequency and voltage scaling code in the Linux(TM) kernel +============================================================================== + +Author: Dominik Brodowski + + Clock scaling allows you to change the clock speed of the CPUs on the + fly. This is a nice method to save battery power, because the lower + the clock speed, the less power the CPU consumes. + + +.. toctree:: + :maxdepth: 1 + +Mailing List +------------ +There is a CPU frequency changing CVS commit and general list where +you can report bugs, problems or submit patches. To post a message, +send an email to linux-pm@vger.kernel.org. + +Links +----- +the FTP archives: +* ftp://ftp.linux.org.uk/pub/linux/cpufreq/ + +how to access the CVS repository: +* http://cvs.arm.linux.org.uk/ + +the CPUFreq Mailing list: +* http://vger.kernel.org/vger-lists.html#linux-pm + +Clock and voltage scaling for the SA-1100: +* http://www.lartmaker.nl/projects/scaling diff --git a/Documentation/cpu-freq/index.txt b/Documentation/cpu-freq/index.txt deleted file mode 100644 index c15e75386a05..000000000000 --- a/Documentation/cpu-freq/index.txt +++ /dev/null @@ -1,56 +0,0 @@ - CPU frequency and voltage scaling code in the Linux(TM) kernel - - - L i n u x C P U F r e q - - - - - Dominik Brodowski - - - - Clock scaling allows you to change the clock speed of the CPUs on the - fly. This is a nice method to save battery power, because the lower - the clock speed, the less power the CPU consumes. - - - -Documents in this directory: ----------------------------- - -amd-powernow.txt - AMD powernow driver specific file. - -core.txt - General description of the CPUFreq core and - of CPUFreq notifiers. - -cpu-drivers.txt - How to implement a new cpufreq processor driver. - -cpufreq-nforce2.txt - nVidia nForce2 platform specific file. - -cpufreq-stats.txt - General description of sysfs cpufreq stats. - -index.txt - File index, Mailing list and Links (this document) - -pcc-cpufreq.txt - PCC cpufreq driver specific file. - - -Mailing List ------------- -There is a CPU frequency changing CVS commit and general list where -you can report bugs, problems or submit patches. To post a message, -send an email to linux-pm@vger.kernel.org. - -Links ------ -the FTP archives: -* ftp://ftp.linux.org.uk/pub/linux/cpufreq/ - -how to access the CVS repository: -* http://cvs.arm.linux.org.uk/ - -the CPUFreq Mailing list: -* http://vger.kernel.org/vger-lists.html#linux-pm - -Clock and voltage scaling for the SA-1100: -* http://www.lartmaker.nl/projects/scaling diff --git a/Documentation/index.rst b/Documentation/index.rst index e99d0bd2589d..4cf37ad1cd1d 100644 --- a/Documentation/index.rst +++ b/Documentation/index.rst @@ -99,6 +99,7 @@ needed). accounting/index block/index cdrom/index + cpu-freq/index ide/index fb/index fpga/index -- cgit v1.2.3 From c460f972d3036dbff73897bf7e4b21bdff7d3eaa Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Tue, 3 Mar 2020 14:52:04 +0100 Subject: docs: cpu-freq: convert core.txt to ReST - Add a SPDX header; - Adjust the document title, based on the original contents of cpu-freq/index.txt; - Use lists where needed; - Comment out the existing text-only index; - use ``foo`` to mark a literal expression with asterisk; - Adjust some title marks; - Add table markups; - Add notes markups; - Some whitespace fixes and new line breaks; - Add it to cpu-freq/index.rst. Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Rafael J. Wysocki --- Documentation/cpu-freq/core.rst | 113 +++++++++++++++++++++++++++++++++++++++ Documentation/cpu-freq/core.txt | 112 -------------------------------------- Documentation/cpu-freq/index.rst | 2 + 3 files changed, 115 insertions(+), 112 deletions(-) create mode 100644 Documentation/cpu-freq/core.rst delete mode 100644 Documentation/cpu-freq/core.txt diff --git a/Documentation/cpu-freq/core.rst b/Documentation/cpu-freq/core.rst new file mode 100644 index 000000000000..33cb90bd1d8f --- /dev/null +++ b/Documentation/cpu-freq/core.rst @@ -0,0 +1,113 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================================================= +General description of the CPUFreq core and CPUFreq notifiers +============================================================= + +Authors: + - Dominik Brodowski + - David Kimdon + - Rafael J. Wysocki + - Viresh Kumar + +.. Contents: + + 1. CPUFreq core and interfaces + 2. CPUFreq notifiers + 3. CPUFreq Table Generation with Operating Performance Point (OPP) + +1. General Information +====================== + +The CPUFreq core code is located in drivers/cpufreq/cpufreq.c. This +cpufreq code offers a standardized interface for the CPUFreq +architecture drivers (those pieces of code that do actual +frequency transitions), as well as to "notifiers". These are device +drivers or other part of the kernel that need to be informed of +policy changes (ex. thermal modules like ACPI) or of all +frequency changes (ex. timing code) or even need to force certain +speed limits (like LCD drivers on ARM architecture). Additionally, the +kernel "constant" loops_per_jiffy is updated on frequency changes +here. + +Reference counting of the cpufreq policies is done by cpufreq_cpu_get +and cpufreq_cpu_put, which make sure that the cpufreq driver is +correctly registered with the core, and will not be unloaded until +cpufreq_put_cpu is called. That also ensures that the respective cpufreq +policy doesn't get freed while being used. + +2. CPUFreq notifiers +==================== + +CPUFreq notifiers conform to the standard kernel notifier interface. +See linux/include/linux/notifier.h for details on notifiers. + +There are two different CPUFreq notifiers - policy notifiers and +transition notifiers. + + +2.1 CPUFreq policy notifiers +---------------------------- + +These are notified when a new policy is created or removed. + +The phase is specified in the second argument to the notifier. The phase is +CPUFREQ_CREATE_POLICY when the policy is first created and it is +CPUFREQ_REMOVE_POLICY when the policy is removed. + +The third argument, a ``void *pointer``, points to a struct cpufreq_policy +consisting of several values, including min, max (the lower and upper +frequencies (in kHz) of the new policy). + + +2.2 CPUFreq transition notifiers +-------------------------------- + +These are notified twice for each online CPU in the policy, when the +CPUfreq driver switches the CPU core frequency and this change has no +any external implications. + +The second argument specifies the phase - CPUFREQ_PRECHANGE or +CPUFREQ_POSTCHANGE. + +The third argument is a struct cpufreq_freqs with the following +values: + +===== =========================== +cpu number of the affected CPU +old old frequency +new new frequency +flags flags of the cpufreq driver +===== =========================== + +3. CPUFreq Table Generation with Operating Performance Point (OPP) +================================================================== +For details about OPP, see Documentation/power/opp.rst + +dev_pm_opp_init_cpufreq_table - + This function provides a ready to use conversion routine to translate + the OPP layer's internal information about the available frequencies + into a format readily providable to cpufreq. + + .. Warning:: + + Do not use this function in interrupt context. + + Example:: + + soc_pm_init() + { + /* Do things */ + r = dev_pm_opp_init_cpufreq_table(dev, &freq_table); + if (!r) + policy->freq_table = freq_table; + /* Do other things */ + } + + .. note:: + + This function is available only if CONFIG_CPU_FREQ is enabled in + addition to CONFIG_PM_OPP. + +dev_pm_opp_free_cpufreq_table + Free up the table allocated by dev_pm_opp_init_cpufreq_table diff --git a/Documentation/cpu-freq/core.txt b/Documentation/cpu-freq/core.txt deleted file mode 100644 index ed577d9c154b..000000000000 --- a/Documentation/cpu-freq/core.txt +++ /dev/null @@ -1,112 +0,0 @@ - CPU frequency and voltage scaling code in the Linux(TM) kernel - - - L i n u x C P U F r e q - - C P U F r e q C o r e - - - Dominik Brodowski - David Kimdon - Rafael J. Wysocki - Viresh Kumar - - - - Clock scaling allows you to change the clock speed of the CPUs on the - fly. This is a nice method to save battery power, because the lower - the clock speed, the less power the CPU consumes. - - -Contents: ---------- -1. CPUFreq core and interfaces -2. CPUFreq notifiers -3. CPUFreq Table Generation with Operating Performance Point (OPP) - -1. General Information -======================= - -The CPUFreq core code is located in drivers/cpufreq/cpufreq.c. This -cpufreq code offers a standardized interface for the CPUFreq -architecture drivers (those pieces of code that do actual -frequency transitions), as well as to "notifiers". These are device -drivers or other part of the kernel that need to be informed of -policy changes (ex. thermal modules like ACPI) or of all -frequency changes (ex. timing code) or even need to force certain -speed limits (like LCD drivers on ARM architecture). Additionally, the -kernel "constant" loops_per_jiffy is updated on frequency changes -here. - -Reference counting of the cpufreq policies is done by cpufreq_cpu_get -and cpufreq_cpu_put, which make sure that the cpufreq driver is -correctly registered with the core, and will not be unloaded until -cpufreq_put_cpu is called. That also ensures that the respective cpufreq -policy doesn't get freed while being used. - -2. CPUFreq notifiers -==================== - -CPUFreq notifiers conform to the standard kernel notifier interface. -See linux/include/linux/notifier.h for details on notifiers. - -There are two different CPUFreq notifiers - policy notifiers and -transition notifiers. - - -2.1 CPUFreq policy notifiers ----------------------------- - -These are notified when a new policy is created or removed. - -The phase is specified in the second argument to the notifier. The phase is -CPUFREQ_CREATE_POLICY when the policy is first created and it is -CPUFREQ_REMOVE_POLICY when the policy is removed. - -The third argument, a void *pointer, points to a struct cpufreq_policy -consisting of several values, including min, max (the lower and upper -frequencies (in kHz) of the new policy). - - -2.2 CPUFreq transition notifiers --------------------------------- - -These are notified twice for each online CPU in the policy, when the -CPUfreq driver switches the CPU core frequency and this change has no -any external implications. - -The second argument specifies the phase - CPUFREQ_PRECHANGE or -CPUFREQ_POSTCHANGE. - -The third argument is a struct cpufreq_freqs with the following -values: -cpu - number of the affected CPU -old - old frequency -new - new frequency -flags - flags of the cpufreq driver - -3. CPUFreq Table Generation with Operating Performance Point (OPP) -================================================================== -For details about OPP, see Documentation/power/opp.rst - -dev_pm_opp_init_cpufreq_table - - This function provides a ready to use conversion routine to translate - the OPP layer's internal information about the available frequencies - into a format readily providable to cpufreq. - - WARNING: Do not use this function in interrupt context. - - Example: - soc_pm_init() - { - /* Do things */ - r = dev_pm_opp_init_cpufreq_table(dev, &freq_table); - if (!r) - policy->freq_table = freq_table; - /* Do other things */ - } - - NOTE: This function is available only if CONFIG_CPU_FREQ is enabled in - addition to CONFIG_PM_OPP. - -dev_pm_opp_free_cpufreq_table - Free up the table allocated by dev_pm_opp_init_cpufreq_table diff --git a/Documentation/cpu-freq/index.rst b/Documentation/cpu-freq/index.rst index 1bff3dfddd23..53501c58f41d 100644 --- a/Documentation/cpu-freq/index.rst +++ b/Documentation/cpu-freq/index.rst @@ -14,6 +14,8 @@ Author: Dominik Brodowski .. toctree:: :maxdepth: 1 + core + Mailing List ------------ There is a CPU frequency changing CVS commit and general list where -- cgit v1.2.3 From 8f92058987a1e3ec851218420ac1ef554aca41fe Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Tue, 3 Mar 2020 14:52:05 +0100 Subject: docs: cpu-freq: convert cpu-drivers.txt to ReST - Add a SPDX header; - Add a document title, based on the original contents of cpu-freq/index.txt; - Use lists where needed; - Comment out the existing text-only index; - Adjust some title marks; - Add table markups; - Add notes markups; - Mark literal blocks as such; - use ``foo`` for literal texts; - Some whitespace fixes and new line breaks; - Add it to cpu-freq/index.rst. Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Rafael J. Wysocki --- Documentation/cpu-freq/cpu-drivers.rst | 292 ++++++++++++++++++++++++++++++++ Documentation/cpu-freq/cpu-drivers.txt | 295 --------------------------------- Documentation/cpu-freq/index.rst | 1 + 3 files changed, 293 insertions(+), 295 deletions(-) create mode 100644 Documentation/cpu-freq/cpu-drivers.rst delete mode 100644 Documentation/cpu-freq/cpu-drivers.txt diff --git a/Documentation/cpu-freq/cpu-drivers.rst b/Documentation/cpu-freq/cpu-drivers.rst new file mode 100644 index 000000000000..a697278ce190 --- /dev/null +++ b/Documentation/cpu-freq/cpu-drivers.rst @@ -0,0 +1,292 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============================================== +How to Implement a new CPUFreq Processor Driver +=============================================== + +Authors: + + + - Dominik Brodowski + - Rafael J. Wysocki + - Viresh Kumar + +.. Contents + + 1. What To Do? + 1.1 Initialization + 1.2 Per-CPU Initialization + 1.3 verify + 1.4 target/target_index or setpolicy? + 1.5 target/target_index + 1.6 setpolicy + 1.7 get_intermediate and target_intermediate + 2. Frequency Table Helpers + + + +1. What To Do? +============== + +So, you just got a brand-new CPU / chipset with datasheets and want to +add cpufreq support for this CPU / chipset? Great. Here are some hints +on what is necessary: + + +1.1 Initialization +------------------ + +First of all, in an __initcall level 7 (module_init()) or later +function check whether this kernel runs on the right CPU and the right +chipset. If so, register a struct cpufreq_driver with the CPUfreq core +using cpufreq_register_driver() + +What shall this struct cpufreq_driver contain? + + .name - The name of this driver. + + .init - A pointer to the per-policy initialization function. + + .verify - A pointer to a "verification" function. + + .setpolicy _or_ .fast_switch _or_ .target _or_ .target_index - See + below on the differences. + +And optionally + + .flags - Hints for the cpufreq core. + + .driver_data - cpufreq driver specific data. + + .resolve_freq - Returns the most appropriate frequency for a target + frequency. Doesn't change the frequency though. + + .get_intermediate and target_intermediate - Used to switch to stable + frequency while changing CPU frequency. + + .get - Returns current frequency of the CPU. + + .bios_limit - Returns HW/BIOS max frequency limitations for the CPU. + + .exit - A pointer to a per-policy cleanup function called during + CPU_POST_DEAD phase of cpu hotplug process. + + .stop_cpu - A pointer to a per-policy stop function called during + CPU_DOWN_PREPARE phase of cpu hotplug process. + + .suspend - A pointer to a per-policy suspend function which is called + with interrupts disabled and _after_ the governor is stopped for the + policy. + + .resume - A pointer to a per-policy resume function which is called + with interrupts disabled and _before_ the governor is started again. + + .ready - A pointer to a per-policy ready function which is called after + the policy is fully initialized. + + .attr - A pointer to a NULL-terminated list of "struct freq_attr" which + allow to export values to sysfs. + + .boost_enabled - If set, boost frequencies are enabled. + + .set_boost - A pointer to a per-policy function to enable/disable boost + frequencies. + + +1.2 Per-CPU Initialization +-------------------------- + +Whenever a new CPU is registered with the device model, or after the +cpufreq driver registers itself, the per-policy initialization function +cpufreq_driver.init is called if no cpufreq policy existed for the CPU. +Note that the .init() and .exit() routines are called only once for the +policy and not for each CPU managed by the policy. It takes a ``struct +cpufreq_policy *policy`` as argument. What to do now? + +If necessary, activate the CPUfreq support on your CPU. + +Then, the driver must fill in the following values: + ++-----------------------------------+--------------------------------------+ +|policy->cpuinfo.min_freq _and_ | | +|policy->cpuinfo.max_freq | the minimum and maximum frequency | +| | (in kHz) which is supported by | +| | this CPU | ++-----------------------------------+--------------------------------------+ +|policy->cpuinfo.transition_latency | the time it takes on this CPU to | +| | switch between two frequencies in | +| | nanoseconds (if appropriate, else | +| | specify CPUFREQ_ETERNAL) | ++-----------------------------------+--------------------------------------+ +|policy->cur | The current operating frequency of | +| | this CPU (if appropriate) | ++-----------------------------------+--------------------------------------+ +|policy->min, | | +|policy->max, | | +|policy->policy and, if necessary, | | +|policy->governor | must contain the "default policy" for| +| | this CPU. A few moments later, | +| | cpufreq_driver.verify and either | +| | cpufreq_driver.setpolicy or | +| | cpufreq_driver.target/target_index is| +| | called with these values. | ++-----------------------------------+--------------------------------------+ +|policy->cpus | Update this with the masks of the | +| | (online + offline) CPUs that do DVFS | +| | along with this CPU (i.e. that share| +| | clock/voltage rails with it). | ++-----------------------------------+--------------------------------------+ + +For setting some of these values (cpuinfo.min[max]_freq, policy->min[max]), the +frequency table helpers might be helpful. See the section 2 for more information +on them. + + +1.3 verify +---------- + +When the user decides a new policy (consisting of +"policy,governor,min,max") shall be set, this policy must be validated +so that incompatible values can be corrected. For verifying these +values cpufreq_verify_within_limits(``struct cpufreq_policy *policy``, +``unsigned int min_freq``, ``unsigned int max_freq``) function might be helpful. +See section 2 for details on frequency table helpers. + +You need to make sure that at least one valid frequency (or operating +range) is within policy->min and policy->max. If necessary, increase +policy->max first, and only if this is no solution, decrease policy->min. + + +1.4 target or target_index or setpolicy or fast_switch? +------------------------------------------------------- + +Most cpufreq drivers or even most cpu frequency scaling algorithms +only allow the CPU frequency to be set to predefined fixed values. For +these, you use the ->target(), ->target_index() or ->fast_switch() +callbacks. + +Some cpufreq capable processors switch the frequency between certain +limits on their own. These shall use the ->setpolicy() callback. + + +1.5. target/target_index +------------------------ + +The target_index call has two arguments: ``struct cpufreq_policy *policy``, +and ``unsigned int`` index (into the exposed frequency table). + +The CPUfreq driver must set the new frequency when called here. The +actual frequency must be determined by freq_table[index].frequency. + +It should always restore to earlier frequency (i.e. policy->restore_freq) in +case of errors, even if we switched to intermediate frequency earlier. + +Deprecated +---------- +The target call has three arguments: ``struct cpufreq_policy *policy``, +unsigned int target_frequency, unsigned int relation. + +The CPUfreq driver must set the new frequency when called here. The +actual frequency must be determined using the following rules: + +- keep close to "target_freq" +- policy->min <= new_freq <= policy->max (THIS MUST BE VALID!!!) +- if relation==CPUFREQ_REL_L, try to select a new_freq higher than or equal + target_freq. ("L for lowest, but no lower than") +- if relation==CPUFREQ_REL_H, try to select a new_freq lower than or equal + target_freq. ("H for highest, but no higher than") + +Here again the frequency table helper might assist you - see section 2 +for details. + +1.6. fast_switch +---------------- + +This function is used for frequency switching from scheduler's context. +Not all drivers are expected to implement it, as sleeping from within +this callback isn't allowed. This callback must be highly optimized to +do switching as fast as possible. + +This function has two arguments: ``struct cpufreq_policy *policy`` and +``unsigned int target_frequency``. + + +1.7 setpolicy +------------- + +The setpolicy call only takes a ``struct cpufreq_policy *policy`` as +argument. You need to set the lower limit of the in-processor or +in-chipset dynamic frequency switching to policy->min, the upper limit +to policy->max, and -if supported- select a performance-oriented +setting when policy->policy is CPUFREQ_POLICY_PERFORMANCE, and a +powersaving-oriented setting when CPUFREQ_POLICY_POWERSAVE. Also check +the reference implementation in drivers/cpufreq/longrun.c + +1.8 get_intermediate and target_intermediate +-------------------------------------------- + +Only for drivers with target_index() and CPUFREQ_ASYNC_NOTIFICATION unset. + +get_intermediate should return a stable intermediate frequency platform wants to +switch to, and target_intermediate() should set CPU to that frequency, before +jumping to the frequency corresponding to 'index'. Core will take care of +sending notifications and driver doesn't have to handle them in +target_intermediate() or target_index(). + +Drivers can return '0' from get_intermediate() in case they don't wish to switch +to intermediate frequency for some target frequency. In that case core will +directly call ->target_index(). + +NOTE: ->target_index() should restore to policy->restore_freq in case of +failures as core would send notifications for that. + + +2. Frequency Table Helpers +========================== + +As most cpufreq processors only allow for being set to a few specific +frequencies, a "frequency table" with some functions might assist in +some work of the processor driver. Such a "frequency table" consists of +an array of struct cpufreq_frequency_table entries, with driver specific +values in "driver_data", the corresponding frequency in "frequency" and +flags set. At the end of the table, you need to add a +cpufreq_frequency_table entry with frequency set to CPUFREQ_TABLE_END. +And if you want to skip one entry in the table, set the frequency to +CPUFREQ_ENTRY_INVALID. The entries don't need to be in sorted in any +particular order, but if they are cpufreq core will do DVFS a bit +quickly for them as search for best match is faster. + +The cpufreq table is verified automatically by the core if the policy contains a +valid pointer in its policy->freq_table field. + +cpufreq_frequency_table_verify() assures that at least one valid +frequency is within policy->min and policy->max, and all other criteria +are met. This is helpful for the ->verify call. + +cpufreq_frequency_table_target() is the corresponding frequency table +helper for the ->target stage. Just pass the values to this function, +and this function returns the of the frequency table entry which +contains the frequency the CPU shall be set to. + +The following macros can be used as iterators over cpufreq_frequency_table: + +cpufreq_for_each_entry(pos, table) - iterates over all entries of frequency +table. + +cpufreq_for_each_valid_entry(pos, table) - iterates over all entries, +excluding CPUFREQ_ENTRY_INVALID frequencies. +Use arguments "pos" - a ``cpufreq_frequency_table *`` as a loop cursor and +"table" - the ``cpufreq_frequency_table *`` you want to iterate over. + +For example:: + + struct cpufreq_frequency_table *pos, *driver_freq_table; + + cpufreq_for_each_entry(pos, driver_freq_table) { + /* Do something with pos */ + pos->frequency = ... + } + +If you need to work with the position of pos within driver_freq_table, +do not subtract the pointers, as it is quite costly. Instead, use the +macros cpufreq_for_each_entry_idx() and cpufreq_for_each_valid_entry_idx(). diff --git a/Documentation/cpu-freq/cpu-drivers.txt b/Documentation/cpu-freq/cpu-drivers.txt deleted file mode 100644 index 6e353d00cdc6..000000000000 --- a/Documentation/cpu-freq/cpu-drivers.txt +++ /dev/null @@ -1,295 +0,0 @@ - CPU frequency and voltage scaling code in the Linux(TM) kernel - - - L i n u x C P U F r e q - - C P U D r i v e r s - - - information for developers - - - - Dominik Brodowski - Rafael J. Wysocki - Viresh Kumar - - - - Clock scaling allows you to change the clock speed of the CPUs on the - fly. This is a nice method to save battery power, because the lower - the clock speed, the less power the CPU consumes. - - -Contents: ---------- -1. What To Do? -1.1 Initialization -1.2 Per-CPU Initialization -1.3 verify -1.4 target/target_index or setpolicy? -1.5 target/target_index -1.6 setpolicy -1.7 get_intermediate and target_intermediate -2. Frequency Table Helpers - - - -1. What To Do? -============== - -So, you just got a brand-new CPU / chipset with datasheets and want to -add cpufreq support for this CPU / chipset? Great. Here are some hints -on what is necessary: - - -1.1 Initialization ------------------- - -First of all, in an __initcall level 7 (module_init()) or later -function check whether this kernel runs on the right CPU and the right -chipset. If so, register a struct cpufreq_driver with the CPUfreq core -using cpufreq_register_driver() - -What shall this struct cpufreq_driver contain? - - .name - The name of this driver. - - .init - A pointer to the per-policy initialization function. - - .verify - A pointer to a "verification" function. - - .setpolicy _or_ .fast_switch _or_ .target _or_ .target_index - See - below on the differences. - -And optionally - - .flags - Hints for the cpufreq core. - - .driver_data - cpufreq driver specific data. - - .resolve_freq - Returns the most appropriate frequency for a target - frequency. Doesn't change the frequency though. - - .get_intermediate and target_intermediate - Used to switch to stable - frequency while changing CPU frequency. - - .get - Returns current frequency of the CPU. - - .bios_limit - Returns HW/BIOS max frequency limitations for the CPU. - - .exit - A pointer to a per-policy cleanup function called during - CPU_POST_DEAD phase of cpu hotplug process. - - .stop_cpu - A pointer to a per-policy stop function called during - CPU_DOWN_PREPARE phase of cpu hotplug process. - - .suspend - A pointer to a per-policy suspend function which is called - with interrupts disabled and _after_ the governor is stopped for the - policy. - - .resume - A pointer to a per-policy resume function which is called - with interrupts disabled and _before_ the governor is started again. - - .ready - A pointer to a per-policy ready function which is called after - the policy is fully initialized. - - .attr - A pointer to a NULL-terminated list of "struct freq_attr" which - allow to export values to sysfs. - - .boost_enabled - If set, boost frequencies are enabled. - - .set_boost - A pointer to a per-policy function to enable/disable boost - frequencies. - - -1.2 Per-CPU Initialization --------------------------- - -Whenever a new CPU is registered with the device model, or after the -cpufreq driver registers itself, the per-policy initialization function -cpufreq_driver.init is called if no cpufreq policy existed for the CPU. -Note that the .init() and .exit() routines are called only once for the -policy and not for each CPU managed by the policy. It takes a struct -cpufreq_policy *policy as argument. What to do now? - -If necessary, activate the CPUfreq support on your CPU. - -Then, the driver must fill in the following values: - -policy->cpuinfo.min_freq _and_ -policy->cpuinfo.max_freq - the minimum and maximum frequency - (in kHz) which is supported by - this CPU -policy->cpuinfo.transition_latency the time it takes on this CPU to - switch between two frequencies in - nanoseconds (if appropriate, else - specify CPUFREQ_ETERNAL) - -policy->cur The current operating frequency of - this CPU (if appropriate) -policy->min, -policy->max, -policy->policy and, if necessary, -policy->governor must contain the "default policy" for - this CPU. A few moments later, - cpufreq_driver.verify and either - cpufreq_driver.setpolicy or - cpufreq_driver.target/target_index is called - with these values. -policy->cpus Update this with the masks of the - (online + offline) CPUs that do DVFS - along with this CPU (i.e. that share - clock/voltage rails with it). - -For setting some of these values (cpuinfo.min[max]_freq, policy->min[max]), the -frequency table helpers might be helpful. See the section 2 for more information -on them. - - -1.3 verify ----------- - -When the user decides a new policy (consisting of -"policy,governor,min,max") shall be set, this policy must be validated -so that incompatible values can be corrected. For verifying these -values cpufreq_verify_within_limits(struct cpufreq_policy *policy, -unsigned int min_freq, unsigned int max_freq) function might be helpful. -See section 2 for details on frequency table helpers. - -You need to make sure that at least one valid frequency (or operating -range) is within policy->min and policy->max. If necessary, increase -policy->max first, and only if this is no solution, decrease policy->min. - - -1.4 target or target_index or setpolicy or fast_switch? -------------------------------------------------------- - -Most cpufreq drivers or even most cpu frequency scaling algorithms -only allow the CPU frequency to be set to predefined fixed values. For -these, you use the ->target(), ->target_index() or ->fast_switch() -callbacks. - -Some cpufreq capable processors switch the frequency between certain -limits on their own. These shall use the ->setpolicy() callback. - - -1.5. target/target_index ------------------------- - -The target_index call has two arguments: struct cpufreq_policy *policy, -and unsigned int index (into the exposed frequency table). - -The CPUfreq driver must set the new frequency when called here. The -actual frequency must be determined by freq_table[index].frequency. - -It should always restore to earlier frequency (i.e. policy->restore_freq) in -case of errors, even if we switched to intermediate frequency earlier. - -Deprecated: ----------- -The target call has three arguments: struct cpufreq_policy *policy, -unsigned int target_frequency, unsigned int relation. - -The CPUfreq driver must set the new frequency when called here. The -actual frequency must be determined using the following rules: - -- keep close to "target_freq" -- policy->min <= new_freq <= policy->max (THIS MUST BE VALID!!!) -- if relation==CPUFREQ_REL_L, try to select a new_freq higher than or equal - target_freq. ("L for lowest, but no lower than") -- if relation==CPUFREQ_REL_H, try to select a new_freq lower than or equal - target_freq. ("H for highest, but no higher than") - -Here again the frequency table helper might assist you - see section 2 -for details. - -1.6. fast_switch ----------------- - -This function is used for frequency switching from scheduler's context. -Not all drivers are expected to implement it, as sleeping from within -this callback isn't allowed. This callback must be highly optimized to -do switching as fast as possible. - -This function has two arguments: struct cpufreq_policy *policy and -unsigned int target_frequency. - - -1.7 setpolicy -------------- - -The setpolicy call only takes a struct cpufreq_policy *policy as -argument. You need to set the lower limit of the in-processor or -in-chipset dynamic frequency switching to policy->min, the upper limit -to policy->max, and -if supported- select a performance-oriented -setting when policy->policy is CPUFREQ_POLICY_PERFORMANCE, and a -powersaving-oriented setting when CPUFREQ_POLICY_POWERSAVE. Also check -the reference implementation in drivers/cpufreq/longrun.c - -1.8 get_intermediate and target_intermediate --------------------------------------------- - -Only for drivers with target_index() and CPUFREQ_ASYNC_NOTIFICATION unset. - -get_intermediate should return a stable intermediate frequency platform wants to -switch to, and target_intermediate() should set CPU to that frequency, before -jumping to the frequency corresponding to 'index'. Core will take care of -sending notifications and driver doesn't have to handle them in -target_intermediate() or target_index(). - -Drivers can return '0' from get_intermediate() in case they don't wish to switch -to intermediate frequency for some target frequency. In that case core will -directly call ->target_index(). - -NOTE: ->target_index() should restore to policy->restore_freq in case of -failures as core would send notifications for that. - - -2. Frequency Table Helpers -========================== - -As most cpufreq processors only allow for being set to a few specific -frequencies, a "frequency table" with some functions might assist in -some work of the processor driver. Such a "frequency table" consists of -an array of struct cpufreq_frequency_table entries, with driver specific -values in "driver_data", the corresponding frequency in "frequency" and -flags set. At the end of the table, you need to add a -cpufreq_frequency_table entry with frequency set to CPUFREQ_TABLE_END. -And if you want to skip one entry in the table, set the frequency to -CPUFREQ_ENTRY_INVALID. The entries don't need to be in sorted in any -particular order, but if they are cpufreq core will do DVFS a bit -quickly for them as search for best match is faster. - -The cpufreq table is verified automatically by the core if the policy contains a -valid pointer in its policy->freq_table field. - -cpufreq_frequency_table_verify() assures that at least one valid -frequency is within policy->min and policy->max, and all other criteria -are met. This is helpful for the ->verify call. - -cpufreq_frequency_table_target() is the corresponding frequency table -helper for the ->target stage. Just pass the values to this function, -and this function returns the of the frequency table entry which -contains the frequency the CPU shall be set to. - -The following macros can be used as iterators over cpufreq_frequency_table: - -cpufreq_for_each_entry(pos, table) - iterates over all entries of frequency -table. - -cpufreq_for_each_valid_entry(pos, table) - iterates over all entries, -excluding CPUFREQ_ENTRY_INVALID frequencies. -Use arguments "pos" - a cpufreq_frequency_table * as a loop cursor and -"table" - the cpufreq_frequency_table * you want to iterate over. - -For example: - - struct cpufreq_frequency_table *pos, *driver_freq_table; - - cpufreq_for_each_entry(pos, driver_freq_table) { - /* Do something with pos */ - pos->frequency = ... - } - -If you need to work with the position of pos within driver_freq_table, -do not subtract the pointers, as it is quite costly. Instead, use the -macros cpufreq_for_each_entry_idx() and cpufreq_for_each_valid_entry_idx(). diff --git a/Documentation/cpu-freq/index.rst b/Documentation/cpu-freq/index.rst index 53501c58f41d..fcc58b2eee01 100644 --- a/Documentation/cpu-freq/index.rst +++ b/Documentation/cpu-freq/index.rst @@ -15,6 +15,7 @@ Author: Dominik Brodowski :maxdepth: 1 core + cpu-drivers Mailing List ------------ -- cgit v1.2.3 From aadfa206e9bb6fcee0b9fcd2fc39804026cdefcc Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Tue, 3 Mar 2020 14:52:06 +0100 Subject: docs: cpu-freq: convert cpufreq-stats.txt to ReST - Add a SPDX header; - Add a document title, based on the original contents of cpu-freq/index.txt; - Use lists where needed; - Comment out the existing text-only index; - Adjust some title marks; - Use bold on some places; - Mark literal blocks as such; - Some whitespace fixes and new line breaks; - Add it to cpu-freq/index.rst. Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Rafael J. Wysocki --- Documentation/cpu-freq/cpufreq-stats.rst | 136 +++++++++++++++++++++++++++++++ Documentation/cpu-freq/cpufreq-stats.txt | 127 ----------------------------- Documentation/cpu-freq/index.rst | 1 + 3 files changed, 137 insertions(+), 127 deletions(-) create mode 100644 Documentation/cpu-freq/cpufreq-stats.rst delete mode 100644 Documentation/cpu-freq/cpufreq-stats.txt diff --git a/Documentation/cpu-freq/cpufreq-stats.rst b/Documentation/cpu-freq/cpufreq-stats.rst new file mode 100644 index 000000000000..9ad695b1c7db --- /dev/null +++ b/Documentation/cpu-freq/cpufreq-stats.rst @@ -0,0 +1,136 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========================================== +General Description of sysfs CPUFreq Stats +========================================== + +information for users + + +Author: Venkatesh Pallipadi + +.. Contents + + 1. Introduction + 2. Statistics Provided (with example) + 3. Configuring cpufreq-stats + + +1. Introduction +=============== + +cpufreq-stats is a driver that provides CPU frequency statistics for each CPU. +These statistics are provided in /sysfs as a bunch of read_only interfaces. This +interface (when configured) will appear in a separate directory under cpufreq +in /sysfs (/devices/system/cpu/cpuX/cpufreq/stats/) for each CPU. +Various statistics will form read_only files under this directory. + +This driver is designed to be independent of any particular cpufreq_driver +that may be running on your CPU. So, it will work with any cpufreq_driver. + + +2. Statistics Provided (with example) +===================================== + +cpufreq stats provides following statistics (explained in detail below). + +- time_in_state +- total_trans +- trans_table + +All the statistics will be from the time the stats driver has been inserted +(or the time the stats were reset) to the time when a read of a particular +statistic is done. Obviously, stats driver will not have any information +about the frequency transitions before the stats driver insertion. + +:: + + :/sys/devices/system/cpu/cpu0/cpufreq/stats # ls -l + total 0 + drwxr-xr-x 2 root root 0 May 14 16:06 . + drwxr-xr-x 3 root root 0 May 14 15:58 .. + --w------- 1 root root 4096 May 14 16:06 reset + -r--r--r-- 1 root root 4096 May 14 16:06 time_in_state + -r--r--r-- 1 root root 4096 May 14 16:06 total_trans + -r--r--r-- 1 root root 4096 May 14 16:06 trans_table + +- **reset** + +Write-only attribute that can be used to reset the stat counters. This can be +useful for evaluating system behaviour under different governors without the +need for a reboot. + +- **time_in_state** + +This gives the amount of time spent in each of the frequencies supported by +this CPU. The cat output will have "