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 To compile this driver as a module, choose M here: the
13 module will be called cpufreq.
15 For details, take a look at <file:Documentation/cpu-freq>.
25 bool "Enable CPUfreq debugging"
27 Say Y here to enable CPUfreq subsystem (including drivers)
28 debugging. You will need to activate it via the kernel
29 command line by passing
33 1 to activate CPUfreq core debugging,
34 2 to activate CPUfreq drivers debugging, and
35 4 to activate CPUfreq governor debugging
38 tristate "CPU frequency translation statistics"
42 This driver exports CPU frequency statistics information through sysfs
45 To compile this driver as a module, choose M here: the
46 module will be called cpufreq_stats.
50 config CPU_FREQ_STAT_DETAILS
51 bool "CPU frequency translation statistics details"
52 depends on CPU_FREQ_STAT
54 This will show detail CPU frequency translation table in sysfs file
59 # Note that it is not currently possible to set the other governors (such as ondemand)
60 # as the default, since if they fail to initialise, cpufreq will be
61 # left in an undefined state.
64 prompt "Default CPUFreq governor"
65 default CPU_FREQ_DEFAULT_GOV_USERSPACE if CPU_FREQ_SA1100 || CPU_FREQ_SA1110
66 default CPU_FREQ_DEFAULT_GOV_PERFORMANCE
68 This option sets which CPUFreq governor shall be loaded at
69 startup. If in doubt, select 'performance'.
71 config CPU_FREQ_DEFAULT_GOV_PERFORMANCE
73 select CPU_FREQ_GOV_PERFORMANCE
75 Use the CPUFreq governor 'performance' as default. This sets
76 the frequency statically to the highest frequency supported by
79 config CPU_FREQ_DEFAULT_GOV_USERSPACE
81 select CPU_FREQ_GOV_USERSPACE
83 Use the CPUFreq governor 'userspace' as default. This allows
84 you to set the CPU frequency manually or when an userspace
85 program shall be able to set the CPU dynamically without having
86 to enable the userspace governor manually.
90 config CPU_FREQ_GOV_PERFORMANCE
91 tristate "'performance' governor"
93 This cpufreq governor sets the frequency statically to the
94 highest available CPU frequency.
96 To compile this driver as a module, choose M here: the
97 module will be called cpufreq_performance.
101 config CPU_FREQ_GOV_POWERSAVE
102 tristate "'powersave' governor"
104 This cpufreq governor sets the frequency statically to the
105 lowest available CPU frequency.
107 To compile this driver as a module, choose M here: the
108 module will be called cpufreq_powersave.
112 config CPU_FREQ_GOV_USERSPACE
113 tristate "'userspace' governor for userspace frequency scaling"
115 Enable this cpufreq governor when you either want to set the
116 CPU frequency manually or when an userspace program shall
117 be able to set the CPU dynamically, like on LART
118 <http://www.lartmaker.nl/>.
120 To compile this driver as a module, choose M here: the
121 module will be called cpufreq_userspace.
123 For details, take a look at <file:Documentation/cpu-freq/>.
127 config CPU_FREQ_GOV_ONDEMAND
128 tristate "'ondemand' cpufreq policy governor"
129 select CPU_FREQ_TABLE
131 'ondemand' - This driver adds a dynamic cpufreq policy governor.
132 The governor does a periodic polling and
133 changes frequency based on the CPU utilization.
134 The support for this governor depends on CPU capability to
135 do fast frequency switching (i.e, very low latency frequency
138 To compile this driver as a module, choose M here: the
139 module will be called cpufreq_ondemand.
141 For details, take a look at linux/Documentation/cpu-freq.
145 config CPU_FREQ_GOV_CONSERVATIVE
146 tristate "'conservative' cpufreq governor"
149 'conservative' - this driver is rather similar to the 'ondemand'
150 governor both in its source code and its purpose, the difference is
151 its optimisation for better suitability in a battery powered
152 environment. The frequency is gracefully increased and decreased
153 rather than jumping to 100% when speed is required.
155 If you have a desktop machine then you should really be considering
156 the 'ondemand' governor instead, however if you are using a laptop,
157 PDA or even an AMD64 based computer (due to the unacceptable
158 step-by-step latency issues between the minimum and maximum frequency
159 transitions in the CPU) you will probably want to use this governor.
161 To compile this driver as a module, choose M here: the
162 module will be called cpufreq_conservative.
164 For details, take a look at linux/Documentation/cpu-freq.