From 61cb5758d3c46bc1ba87694fefc0d9653613ce6b Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Date: Wed, 5 Dec 2018 23:45:34 +0100
Subject: [PATCH] cpuidle: Add cpuidle.governor= command line parameter
Add cpuidle.governor= command line parameter to allow the default
cpuidle governor to be replaced.
That is useful, for example, if someone running a tickful kernel
wants to use the menu governor on it.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
Documentation/admin-guide/kernel-parameters.txt | 3 +++
Documentation/admin-guide/pm/cpuidle.rst | 7 +++++++
drivers/cpuidle/cpuidle.c | 1 +
drivers/cpuidle/cpuidle.h | 1 +
drivers/cpuidle/governor.c | 9 +++++++--
5 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 19f4423e70d91..60fb9913af48a 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -674,6 +674,9 @@
cpuidle.off=1 [CPU_IDLE]
disable the cpuidle sub-system
+ cpuidle.governor=
+ [CPU_IDLE] Name of the cpuidle governor to use.
+
cpufreq.off=1 [CPU_FREQ]
disable the cpufreq sub-system
diff --git a/Documentation/admin-guide/pm/cpuidle.rst b/Documentation/admin-guide/pm/cpuidle.rst
index 80b4f26547ac6..9a34484fd6e45 100644
--- a/Documentation/admin-guide/pm/cpuidle.rst
+++ b/Documentation/admin-guide/pm/cpuidle.rst
@@ -566,6 +566,13 @@ processors implementing the architecture (i.e. CPU instruction set) in question,
however, so it is rather crude and not very energy-efficient. For this reason,
it is not recommended for production use.
+The ``cpuidle.governor=`` kernel command line switch allows the ``CPUIdle``
+governor to use to be specified. It has to be appended with a string matching
+the name of an available governor (e.g. ``cpuidle.governor=menu``) and that
+governor will be used instead of the default one. It is possible to force
+the ``menu`` governor to be used on the systems that use the ``ladder`` governor
+by default this way, for example.
+
The other kernel command line parameters controlling CPU idle time management
described below are only relevant for the *x86* architecture and some of
them affect Intel processors only.
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 4a97446f66d83..f7c58043e50f3 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -702,4 +702,5 @@ static int __init cpuidle_init(void)
}
module_param(off, int, 0444);
+module_param_string(governor, param_governor, CPUIDLE_NAME_LEN, 0444);
core_initcall(cpuidle_init);
diff --git a/drivers/cpuidle/cpuidle.h b/drivers/cpuidle/cpuidle.h
index 2965ab32a583f..d6613101af924 100644
--- a/drivers/cpuidle/cpuidle.h
+++ b/drivers/cpuidle/cpuidle.h
@@ -7,6 +7,7 @@
#define __DRIVER_CPUIDLE_H
/* For internal use only */
+extern char param_governor[];
extern struct cpuidle_governor *cpuidle_curr_governor;
extern struct list_head cpuidle_governors;
extern struct list_head cpuidle_detected_devices;
diff --git a/drivers/cpuidle/governor.c b/drivers/cpuidle/governor.c
index 9fed1b8292927..bb93e5cf6a4ae 100644
--- a/drivers/cpuidle/governor.c
+++ b/drivers/cpuidle/governor.c
@@ -11,10 +11,13 @@
#include <linux/cpu.h>
#include <linux/cpuidle.h>
#include <linux/mutex.h>
+#include <linux/module.h>
#include <linux/pm_qos.h>
#include "cpuidle.h"
+char param_governor[CPUIDLE_NAME_LEN];
+
LIST_HEAD(cpuidle_governors);
struct cpuidle_governor *cpuidle_curr_governor;
@@ -86,9 +89,11 @@ int cpuidle_register_governor(struct cpuidle_governor *gov)
mutex_lock(&cpuidle_lock);
if (__cpuidle_find_governor(gov->name) == NULL) {
ret = 0;
- list_add_tail(&gov->governor_list, &cpuidle_governors);
if (!cpuidle_curr_governor ||
- cpuidle_curr_governor->rating < gov->rating)
+ !strncasecmp(param_governor, gov->name, CPUIDLE_NAME_LEN) ||
+ (cpuidle_curr_governor->rating < gov->rating &&
+ strncasecmp(param_governor, cpuidle_curr_governor->name,
+ CPUIDLE_NAME_LEN)))
cpuidle_switch_governor(gov);
}
mutex_unlock(&cpuidle_lock);
--
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