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-rw-r--r--Documentation/cpu-freq/user-guide.txt64
1 files changed, 35 insertions, 29 deletions
diff --git a/Documentation/cpu-freq/user-guide.txt b/Documentation/cpu-freq/user-guide.txt
index 109e97bbab77..391da64e9492 100644
--- a/Documentation/cpu-freq/user-guide.txt
+++ b/Documentation/cpu-freq/user-guide.txt
@@ -18,7 +18,7 @@
Contents:
---------
1. Supported Architectures and Processors
-1.1 ARM
+1.1 ARM and ARM64
1.2 x86
1.3 sparc64
1.4 ppc
@@ -37,16 +37,10 @@ Contents:
1. Supported Architectures and Processors
=========================================
-1.1 ARM
--------
-
-The following ARM processors are supported by cpufreq:
-
-ARM Integrator
-ARM-SA1100
-ARM-SA1110
-Intel PXA
+1.1 ARM and ARM64
+-----------------
+Almost all ARM and ARM64 platforms support CPU frequency scaling.
1.2 x86
-------
@@ -69,6 +63,7 @@ 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.
@@ -87,7 +82,9 @@ UltraSPARC-III
-------
Several "PowerBook" and "iBook2" notebooks are supported.
-
+The following POWER processors are supported in powernv mode:
+POWER8
+POWER9
1.5 SuperH
----------
@@ -147,10 +144,19 @@ 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
@@ -163,25 +169,30 @@ cpuinfo_transition_latency The time it takes on this CPU to
userspace daemon. Make sure to not
switch the frequency too often
resulting in performance loss.
-scaling_driver : this file shows what cpufreq driver is
- used to set the frequency on this CPU
+
+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.
-cpuinfo_cur_freq : Current frequency of the CPU as obtained from
- the hardware, in KHz. This is the frequency
- the CPU actually runs at.
-
-scaling_available_frequencies : List of available frequencies, in KHz.
-
scaling_min_freq and
scaling_max_freq show the current "policy limits" (in
kHz). By echoing new values into these
@@ -190,16 +201,11 @@ scaling_max_freq show the current "policy limits" (in
first set scaling_max_freq, then
scaling_min_freq.
-affected_cpus : List of Online CPUs that require software
- coordination of frequency.
-
-related_cpus : List of Online + Offline CPUs that need software
- coordination of frequency.
-
-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_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