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diff --git a/Documentation/cpu-freq/user-guide.txt b/Documentation/cpu-freq/user-guide.txt deleted file mode 100644 index 391da64e9492..000000000000 --- a/Documentation/cpu-freq/user-guide.txt +++ /dev/null @@ -1,228 +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 - - U S E R G U I D E - - - Dominik Brodowski <linux@brodo.de> - - - - 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. Supported Architectures and Processors -1.1 ARM and ARM64 -1.2 x86 -1.3 sparc64 -1.4 ppc -1.5 SuperH -1.6 Blackfin - -2. "Policy" / "Governor"? -2.1 Policy -2.2 Governor - -3. How to change the CPU cpufreq policy and/or speed -3.1 Preferred interface: sysfs - - - -1. Supported Architectures and Processors -========================================= - -1.1 ARM and ARM64 ------------------ - -Almost all ARM and ARM64 platforms support CPU frequency scaling. - -1.2 x86 -------- - -The following processors for the x86 architecture are supported by cpufreq: - -AMD Elan - SC400, SC410 -AMD mobile K6-2+ -AMD mobile K6-3+ -AMD mobile Duron -AMD mobile Athlon -AMD Opteron -AMD Athlon 64 -Cyrix Media GXm -Intel mobile PIII and Intel mobile PIII-M on certain chipsets -Intel Pentium 4, Intel Xeon -Intel Pentium M (Centrino) -National Semiconductors Geode GX -Transmeta Crusoe -Transmeta Efficeon -VIA Cyrix 3 / C3 -various processors on some ACPI 2.0-compatible systems [*] -And many more - -[*] Only if "ACPI Processor Performance States" are available -to the ACPI<->BIOS interface. - - -1.3 sparc64 ------------ - -The following processors for the sparc64 architecture are supported by -cpufreq: - -UltraSPARC-III - - -1.4 ppc -------- - -Several "PowerBook" and "iBook2" notebooks are supported. -The following POWER processors are supported in powernv mode: -POWER8 -POWER9 - -1.5 SuperH ----------- - -All SuperH processors supporting rate rounding through the clock -framework are supported by cpufreq. - -1.6 Blackfin ------------- - -The following Blackfin processors are supported by cpufreq: - -BF522, BF523, BF524, BF525, BF526, BF527, Rev 0.1 or higher -BF531, BF532, BF533, Rev 0.3 or higher -BF534, BF536, BF537, Rev 0.2 or higher -BF561, Rev 0.3 or higher -BF542, BF544, BF547, BF548, BF549, Rev 0.1 or higher - - -2. "Policy" / "Governor" ? -========================== - -Some CPU frequency scaling-capable processor switch between various -frequencies and operating voltages "on the fly" without any kernel or -user involvement. This guarantees very fast switching to a frequency -which is high enough to serve the user's needs, but low enough to save -power. - - -2.1 Policy ----------- - -On these systems, all you can do is select the lower and upper -frequency limit as well as whether you want more aggressive -power-saving or more instantly available processing power. - - -2.2 Governor ------------- - -On all other cpufreq implementations, these boundaries still need to -be set. Then, a "governor" must be selected. Such a "governor" decides -what speed the processor shall run within the boundaries. One such -"governor" is the "userspace" governor. This one allows the user - or -a yet-to-implement userspace program - to decide what specific speed -the processor shall run at. - - -3. How to change the CPU cpufreq policy and/or speed -==================================================== - -3.1 Preferred Interface: sysfs ------------------------------- - -The preferred interface is located in the sysfs filesystem. If you -mounted it at /sys, the cpufreq interface is located in a subdirectory -"cpufreq" within the cpu-device directory -(e.g. /sys/devices/system/cpu/cpu0/cpufreq/ for the first CPU). - -affected_cpus : List of Online CPUs that require software - coordination of frequency. - -cpuinfo_cur_freq : Current frequency of the CPU as obtained from - the hardware, in KHz. This is the frequency - the CPU actually runs at. - -cpuinfo_min_freq : this file shows the minimum operating - frequency the processor can run at(in kHz) - -cpuinfo_max_freq : this file shows the maximum operating - frequency the processor can run at(in kHz) - -cpuinfo_transition_latency The time it takes on this CPU to - switch between two frequencies in nano - seconds. If unknown or known to be - that high that the driver does not - work with the ondemand governor, -1 - (CPUFREQ_ETERNAL) will be returned. - Using this information can be useful - to choose an appropriate polling - frequency for a kernel governor or - userspace daemon. Make sure to not - switch the frequency too often - resulting in performance loss. - -related_cpus : List of Online + Offline CPUs that need software - coordination of frequency. - -scaling_available_frequencies : List of available frequencies, in KHz. - -scaling_available_governors : this file shows the CPUfreq governors - available in this kernel. You can see the - currently activated governor in - -scaling_cur_freq : Current frequency of the CPU as determined by - the governor and cpufreq core, in KHz. This is - the frequency the kernel thinks the CPU runs - at. - -scaling_driver : this file shows what cpufreq driver is - used to set the frequency on this CPU - -scaling_governor, and by "echoing" the name of another - governor you can change it. Please note - that some governors won't load - they only - work on some specific architectures or - processors. - -scaling_min_freq and -scaling_max_freq show the current "policy limits" (in - kHz). By echoing new values into these - files, you can change these limits. - NOTE: when setting a policy you need to - first set scaling_max_freq, then - scaling_min_freq. - -scaling_setspeed This can be read to get the currently programmed - value by the governor. This can be written to - change the current frequency for a group of - CPUs, represented by a policy. This is supported - currently only by the userspace governor. - -bios_limit : If the BIOS tells the OS to limit a CPU to - lower frequencies, the user can read out the - maximum available frequency from this file. - This typically can happen through (often not - intended) BIOS settings, restrictions - triggered through a service processor or other - BIOS/HW based implementations. - This does not cover thermal ACPI limitations - which can be detected through the generic - thermal driver. - -If you have selected the "userspace" governor which allows you to -set the CPU operating frequency to a specific value, you can read out -the current frequency in - -scaling_setspeed. By "echoing" a new frequency into this - you can change the speed of the CPU, - but only within the limits of - scaling_min_freq and scaling_max_freq. |