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authorRafael J. Wysocki2014-01-17 02:01:32 +0100
committerRafael J. Wysocki2014-01-17 02:01:32 +0100
commit7744064731a9543105e207504e0262f883bc14c0 (patch)
treec3ca5afdd019f56086104c524dd62ea6e779d2d2 /Documentation
parentMerge branches 'acpi-tools' and 'pm-tools' (diff)
parentthermal: exynos: boost: Automatic enable/disable of BOOST feature (at Exynos4... (diff)
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Merge branch 'pm-cpufreq'
* pm-cpufreq: (40 commits) thermal: exynos: boost: Automatic enable/disable of BOOST feature (at Exynos4412) cpufreq: exynos4x12: Change L0 driver data to CPUFREQ_BOOST_FREQ Documentation: cpufreq / boost: Update BOOST documentation cpufreq: exynos: Extend Exynos cpufreq driver to support boost cpufreq / boost: Kconfig: Support for software-managed BOOST acpi-cpufreq: Adjust the code to use the common boost attribute cpufreq: Add boost frequency support in core intel_pstate: Add trace point to report internal state. cpufreq: introduce cpufreq_generic_get() routine ARM: SA1100: Create dummy clk_get_rate() to avoid build failures cpufreq: stats: create sysfs entries when cpufreq_stats is a module cpufreq: stats: free table and remove sysfs entry in a single routine cpufreq: stats: remove hotplug notifiers cpufreq: stats: handle cpufreq_unregister_driver() and suspend/resume properly cpufreq: speedstep: remove unused speedstep_get_state powernow-k6: reorder frequencies powernow-k6: correctly initialize default parameters powernow-k6: disable cache when changing frequency Documentation: add ABI entry for intel_pstate cpufreq: exynos: Convert exynos-cpufreq to platform driver ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/ABI/testing/sysfs-devices-system-cpu24
-rw-r--r--Documentation/cpu-freq/boost.txt26
-rw-r--r--Documentation/cpu-freq/intel-pstate.txt40
3 files changed, 77 insertions, 13 deletions
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 468e4d48f884..d5a0d33c571f 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -200,3 +200,27 @@ Description: address and size of the percpu note.
note of cpu#.
crash_notes_size: size of the note of cpu#.
+
+
+What: /sys/devices/system/cpu/intel_pstate/max_perf_pct
+ /sys/devices/system/cpu/intel_pstate/min_perf_pct
+ /sys/devices/system/cpu/intel_pstate/no_turbo
+Date: February 2013
+Contact: linux-pm@vger.kernel.org
+Description: Parameters for the Intel P-state driver
+
+ Logic for selecting the current P-state in Intel
+ Sandybridge+ processors. The three knobs control
+ limits for the P-state that will be requested by the
+ driver.
+
+ max_perf_pct: limits the maximum P state that will be requested by
+ the driver stated as a percentage of the available performance.
+
+ min_perf_pct: limits the minimum P state that will be requested by
+ the driver stated as a percentage of the available performance.
+
+ no_turbo: limits the driver to selecting P states below the turbo
+ frequency range.
+
+ More details can be found in Documentation/cpu-freq/intel-pstate.txt
diff --git a/Documentation/cpu-freq/boost.txt b/Documentation/cpu-freq/boost.txt
index 9b4edfcf486f..dd62e1334f0a 100644
--- a/Documentation/cpu-freq/boost.txt
+++ b/Documentation/cpu-freq/boost.txt
@@ -17,8 +17,8 @@ Introduction
Some CPUs support a functionality to raise the operating frequency of
some cores in a multi-core package if certain conditions apply, mostly
if the whole chip is not fully utilized and below it's intended thermal
-budget. This is done without operating system control by a combination
-of hardware and firmware.
+budget. The decision about boost disable/enable is made either at hardware
+(e.g. x86) or software (e.g ARM).
On Intel CPUs this is called "Turbo Boost", AMD calls it "Turbo-Core",
in technical documentation "Core performance boost". In Linux we use
the term "boost" for convenience.
@@ -48,24 +48,24 @@ be desirable:
User controlled switch
----------------------
-To allow the user to toggle the boosting functionality, the acpi-cpufreq
-driver exports a sysfs knob to disable it. There is a file:
+To allow the user to toggle the boosting functionality, the cpufreq core
+driver exports a sysfs knob to enable or disable it. There is a file:
/sys/devices/system/cpu/cpufreq/boost
which can either read "0" (boosting disabled) or "1" (boosting enabled).
-Reading the file is always supported, even if the processor does not
-support boosting. In this case the file will be read-only and always
-reads as "0". Explicitly changing the permissions and writing to that
-file anyway will return EINVAL.
+The file is exported only when cpufreq driver supports boosting.
+Explicitly changing the permissions and writing to that file anyway will
+return EINVAL.
On supported CPUs one can write either a "0" or a "1" into this file.
This will either disable the boost functionality on all cores in the
-whole system (0) or will allow the hardware to boost at will (1).
+whole system (0) or will allow the software or hardware to boost at will
+(1).
Writing a "1" does not explicitly boost the system, but just allows the
-CPU (and the firmware) to boost at their discretion. Some implementations
-take external factors like the chip's temperature into account, so
-boosting once does not necessarily mean that it will occur every time
-even using the exact same software setup.
+CPU to boost at their discretion. Some implementations take external
+factors like the chip's temperature into account, so boosting once does
+not necessarily mean that it will occur every time even using the exact
+same software setup.
AMD legacy cpb switch
diff --git a/Documentation/cpu-freq/intel-pstate.txt b/Documentation/cpu-freq/intel-pstate.txt
new file mode 100644
index 000000000000..e742d21dbd96
--- /dev/null
+++ b/Documentation/cpu-freq/intel-pstate.txt
@@ -0,0 +1,40 @@
+Intel P-state driver
+--------------------
+
+This driver implements a scaling driver with an internal governor for
+Intel Core processors. The driver follows the same model as the
+Transmeta scaling driver (longrun.c) and implements the setpolicy()
+instead of target(). Scaling drivers that implement setpolicy() are
+assumed to implement internal governors by the cpufreq core. All the
+logic for selecting the current P state is contained within the
+driver; no external governor is used by the cpufreq core.
+
+Intel SandyBridge+ processors are supported.
+
+New sysfs files for controlling P state selection have been added to
+/sys/devices/system/cpu/intel_pstate/
+
+ max_perf_pct: limits the maximum P state that will be requested by
+ the driver stated as a percentage of the available performance.
+
+ min_perf_pct: limits the minimum P state that will be requested by
+ the driver stated as a percentage of the available performance.
+
+ no_turbo: limits the driver to selecting P states below the turbo
+ frequency range.
+
+For contemporary Intel processors, the frequency is controlled by the
+processor itself and the P-states exposed to software are related to
+performance levels. The idea that frequency can be set to a single
+frequency is fiction for Intel Core processors. Even if the scaling
+driver selects a single P state the actual frequency the processor
+will run at is selected by the processor itself.
+
+New debugfs files have also been added to /sys/kernel/debug/pstate_snb/
+
+ deadband
+ d_gain_pct
+ i_gain_pct
+ p_gain_pct
+ sample_rate_ms
+ setpoint