linux-kernel - [PATCH] Documentation, intel_pstate: Add a description of the intel

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Date:	Thu,  5 Jun 2014 13:21:51 -0400
From:	Prarit Bhargava <prarit@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Prarit Bhargava <prarit@...hat.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Dirk Brandewie <dirk.brandewie@...il.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Russell King <linux@....linux.org.uk>,
	Jesper Nilsson <jesper.nilsson@...s.com>,
	"David S. Miller" <davem@...emloft.net>,
	Ramkumar Ramachandra <artagnon@...il.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>, linux-doc@...r.kernel.org
Subject: [PATCH] Documentation, intel_pstate: Add a description of the intel_pstate internal governors [v3]

The current documentation is incomplete wrt the intel_pstate internal
governors.  The confusion comes from the general use internal governors
which also use the names performance and powersave.  This patch
differentiates between the two sets of governors.

Cc: Viresh Kumar <viresh.kumar@...aro.org>
Cc: Dirk Brandewie <dirk.brandewie@...il.com>
Cc: Randy Dunlap <rdunlap@...radead.org>
Cc: Russell King <linux@....linux.org.uk>
Cc: Jesper Nilsson <jesper.nilsson@...s.com>
Cc: Viresh Kumar <viresh.kumar@...aro.org>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Ramkumar Ramachandra <artagnon@...il.com>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: linux-doc@...r.kernel.org
Signed-off-by: Prarit Bhargava <prarit@...hat.com>

[v2]: text update
[v3]: text update
---
 Documentation/cpu-freq/governors.txt    |    2 +-
 Documentation/cpu-freq/intel-pstate.txt |    8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/Documentation/cpu-freq/governors.txt b/Documentation/cpu-freq/governors.txt
index 77ec215..c15aa75 100644
--- a/Documentation/cpu-freq/governors.txt
+++ b/Documentation/cpu-freq/governors.txt
@@ -36,7 +36,7 @@ Contents:
 1. What Is A CPUFreq Governor?
 ==============================
 
-Most cpufreq drivers (in fact, all except one, longrun) or even most
+Most cpufreq drivers (except the intel_pstate and longrun) or even most
 cpu frequency scaling algorithms only offer the CPU to be set to one
 frequency. In order to offer dynamic frequency scaling, the cpufreq
 core must be able to tell these drivers of a "target frequency". So
diff --git a/Documentation/cpu-freq/intel-pstate.txt b/Documentation/cpu-freq/intel-pstate.txt
index e742d21..7e9db8f 100644
--- a/Documentation/cpu-freq/intel-pstate.txt
+++ b/Documentation/cpu-freq/intel-pstate.txt
@@ -9,6 +9,14 @@ 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.
 
+The Intel P-state driver has two internal governors, performance and
+powersave.  These governors differ from the generally used governors of the
+same name in the kernel.  The internal performance governor sets the
+max_perf_pct and min_perf_pct to 100; that is, the governor selects the
+highest available P state to maximize the performance of the core.  The
+internal powersave governor selects the appropriate P state based on the
+current load on the CPU.
+
 Intel SandyBridge+ processors are supported.
 
 New sysfs files for controlling P state selection have been added to
-- 
1.7.9.3

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