2 bool "CPU Frequency scaling"
4 CPU Frequency scaling allows you to change the clock speed of
5 CPUs on the fly. This is a nice method to save power, because
6 the lower the CPU clock speed, the less power the CPU consumes.
8 Note that this driver doesn't automatically change the CPU
9 clock speed, you need to either enable a dynamic cpufreq governor
10 (see below) after boot, or use a userspace tool.
12 For details, take a look at <file:Documentation/cpu-freq>.
22 bool "Enable CPUfreq debugging"
24 Say Y here to enable CPUfreq subsystem (including drivers)
25 debugging. You will need to activate it via the kernel
26 command line by passing
30 1 to activate CPUfreq core debugging,
31 2 to activate CPUfreq drivers debugging, and
32 4 to activate CPUfreq governor debugging
35 tristate "CPU frequency translation statistics"
39 This driver exports CPU frequency statistics information through sysfs
42 To compile this driver as a module, choose M here: the
43 module will be called cpufreq_stats.
47 config CPU_FREQ_STAT_DETAILS
48 bool "CPU frequency translation statistics details"
49 depends on CPU_FREQ_STAT
51 This will show detail CPU frequency translation table in sysfs file
56 config CPU_FREQ_TICKLE
57 bool "Enable CPU tickling from drivers and users"
59 This will open sysfs interfaces and export cpufreq_ticlke_cpu
60 function so that drivers and users can tickle a CPU; i.e., force
61 the CPU to operate at (or faster than) the specified (by percent to
62 the maximum) frequency at the moment of call. However, with variable
63 cpufreq governors such as ondemand and conservative, the frequency
64 will keep changing after tickling. Tickle-CPU is intended to provide
65 faster user-response time for ondemand and conservative; e.g., touch
66 screen driver tickles cpus when a user touches the screen. Tickling
67 cpus in such cases reduces the response time required for governors
68 to kick in after measuring cpuidle time.
71 prompt "Default CPUFreq governor"
72 default CPU_FREQ_DEFAULT_GOV_USERSPACE if CPU_FREQ_SA1100 || CPU_FREQ_SA1110
73 default CPU_FREQ_DEFAULT_GOV_PERFORMANCE
75 This option sets which CPUFreq governor shall be loaded at
76 startup. If in doubt, select 'performance'.
78 config CPU_FREQ_DEFAULT_GOV_PERFORMANCE
80 select CPU_FREQ_GOV_PERFORMANCE
82 Use the CPUFreq governor 'performance' as default. This sets
83 the frequency statically to the highest frequency supported by
86 config CPU_FREQ_DEFAULT_GOV_POWERSAVE
89 select CPU_FREQ_GOV_POWERSAVE
91 Use the CPUFreq governor 'powersave' as default. This sets
92 the frequency statically to the lowest frequency supported by
95 config CPU_FREQ_DEFAULT_GOV_USERSPACE
97 select CPU_FREQ_GOV_USERSPACE
99 Use the CPUFreq governor 'userspace' as default. This allows
100 you to set the CPU frequency manually or when a userspace
101 program shall be able to set the CPU dynamically without having
102 to enable the userspace governor manually.
104 config CPU_FREQ_DEFAULT_GOV_ONDEMAND
106 select CPU_FREQ_GOV_ONDEMAND
107 select CPU_FREQ_GOV_PERFORMANCE
109 Use the CPUFreq governor 'ondemand' as default. This allows
110 you to get a full dynamic frequency capable system by simply
111 loading your cpufreq low-level hardware driver.
112 Be aware that not all cpufreq drivers support the ondemand
113 governor. If unsure have a look at the help section of the
114 driver. Fallback governor will be the performance governor.
116 config CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
118 select CPU_FREQ_GOV_CONSERVATIVE
119 select CPU_FREQ_GOV_PERFORMANCE
121 Use the CPUFreq governor 'conservative' as default. This allows
122 you to get a full dynamic frequency capable system by simply
123 loading your cpufreq low-level hardware driver.
124 Be aware that not all cpufreq drivers support the conservative
125 governor. If unsure have a look at the help section of the
126 driver. Fallback governor will be the performance governor.
129 config CPU_FREQ_GOV_PERFORMANCE
130 tristate "'performance' governor"
132 This cpufreq governor sets the frequency statically to the
133 highest available CPU frequency.
135 To compile this driver as a module, choose M here: the
136 module will be called cpufreq_performance.
140 config CPU_FREQ_GOV_POWERSAVE
141 tristate "'powersave' governor"
143 This cpufreq governor sets the frequency statically to the
144 lowest available CPU frequency.
146 To compile this driver as a module, choose M here: the
147 module will be called cpufreq_powersave.
151 config CPU_FREQ_GOV_USERSPACE
152 tristate "'userspace' governor for userspace frequency scaling"
154 Enable this cpufreq governor when you either want to set the
155 CPU frequency manually or when a userspace program shall
156 be able to set the CPU dynamically, like on LART
157 <http://www.lartmaker.nl/>.
159 To compile this driver as a module, choose M here: the
160 module will be called cpufreq_userspace.
162 For details, take a look at <file:Documentation/cpu-freq/>.
166 config CPU_FREQ_GOV_ONDEMAND
167 tristate "'ondemand' cpufreq policy governor"
168 select CPU_FREQ_TABLE
170 'ondemand' - This driver adds a dynamic cpufreq policy governor.
171 The governor does a periodic polling and
172 changes frequency based on the CPU utilization.
173 The support for this governor depends on CPU capability to
174 do fast frequency switching (i.e, very low latency frequency
177 To compile this driver as a module, choose M here: the
178 module will be called cpufreq_ondemand.
180 For details, take a look at linux/Documentation/cpu-freq.
184 config CPU_FREQ_GOV_ONDEMAND_FLEXRATE
185 bool "flexrate interface for 'ondemand' cpufreq policy governor"
186 depends on CPU_FREQ_GOV_ONDEMAND
188 Flexrate for 'ondemand' governor provides an interface to request
189 faster polling temporarily. This is to let it react quickly to
190 load changes when there is high probablity of load increase
191 in short time. For example, when a user event occurs, we have
192 use this interface. It does not increase the frequency
193 unconditionally; however, it allows ondemand to react fast
194 by temporarily decreasing sampling rate. Flexrate provides both
195 sysfs interface and in-kernel interface.
197 config CPU_FREQ_GOV_ONDEMAND_FLEXRATE_MAX_DURATION
198 int "flexrate's maximum duration of sampling rate override"
200 depends on CPU_FREQ_GOV_ONDEMAND_FLEXRATE
203 The maximum number of ondemand sampling whose rate is
204 overriden by Flexrate for ondemand.
206 config CPU_FREQ_GOV_CONSERVATIVE
207 tristate "'conservative' cpufreq governor"
210 'conservative' - this driver is rather similar to the 'ondemand'
211 governor both in its source code and its purpose, the difference is
212 its optimisation for better suitability in a battery powered
213 environment. The frequency is gracefully increased and decreased
214 rather than jumping to 100% when speed is required.
216 If you have a desktop machine then you should really be considering
217 the 'ondemand' governor instead, however if you are using a laptop,
218 PDA or even an AMD64 based computer (due to the unacceptable
219 step-by-step latency issues between the minimum and maximum frequency
220 transitions in the CPU) you will probably want to use this governor.
222 To compile this driver as a module, choose M here: the
223 module will be called cpufreq_conservative.
225 For details, take a look at linux/Documentation/cpu-freq.