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
57 prompt "Default CPUFreq governor"
58 default CPU_FREQ_DEFAULT_GOV_USERSPACE if CPU_FREQ_SA1100 || CPU_FREQ_SA1110
59 default CPU_FREQ_DEFAULT_GOV_PERFORMANCE
61 This option sets which CPUFreq governor shall be loaded at
62 startup. If in doubt, select 'performance'.
64 config CPU_FREQ_DEFAULT_GOV_PERFORMANCE
66 select CPU_FREQ_GOV_PERFORMANCE
68 Use the CPUFreq governor 'performance' as default. This sets
69 the frequency statically to the highest frequency supported by
72 config CPU_FREQ_DEFAULT_GOV_USERSPACE
74 select CPU_FREQ_GOV_USERSPACE
76 Use the CPUFreq governor 'userspace' as default. This allows
77 you to set the CPU frequency manually or when an userspace
78 program shall be able to set the CPU dynamically without having
79 to enable the userspace governor manually.
81 config CPU_FREQ_DEFAULT_GOV_ONDEMAND
83 select CPU_FREQ_GOV_ONDEMAND
84 select CPU_FREQ_GOV_PERFORMANCE
86 Use the CPUFreq governor 'ondemand' as default. This allows
87 you to get a full dynamic frequency capable system by simply
88 loading your cpufreq low-level hardware driver.
89 Be aware that not all cpufreq drivers support the ondemand
90 governor. If unsure have a look at the help section of the
91 driver. Fallback governor will be the performance governor.
93 config CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
95 select CPU_FREQ_GOV_CONSERVATIVE
96 select CPU_FREQ_GOV_PERFORMANCE
98 Use the CPUFreq governor 'conservative' as default. This allows
99 you to get a full dynamic frequency capable system by simply
100 loading your cpufreq low-level hardware driver.
101 Be aware that not all cpufreq drivers support the conservative
102 governor. If unsure have a look at the help section of the
103 driver. Fallback governor will be the performance governor.
106 config CPU_FREQ_GOV_PERFORMANCE
107 tristate "'performance' governor"
109 This cpufreq governor sets the frequency statically to the
110 highest available CPU frequency.
112 To compile this driver as a module, choose M here: the
113 module will be called cpufreq_performance.
117 config CPU_FREQ_GOV_POWERSAVE
118 tristate "'powersave' governor"
120 This cpufreq governor sets the frequency statically to the
121 lowest available CPU frequency.
123 To compile this driver as a module, choose M here: the
124 module will be called cpufreq_powersave.
128 config CPU_FREQ_GOV_USERSPACE
129 tristate "'userspace' governor for userspace frequency scaling"
131 Enable this cpufreq governor when you either want to set the
132 CPU frequency manually or when an userspace program shall
133 be able to set the CPU dynamically, like on LART
134 <http://www.lartmaker.nl/>.
136 To compile this driver as a module, choose M here: the
137 module will be called cpufreq_userspace.
139 For details, take a look at <file:Documentation/cpu-freq/>.
143 config CPU_FREQ_GOV_ONDEMAND
144 tristate "'ondemand' cpufreq policy governor"
145 select CPU_FREQ_TABLE
147 'ondemand' - This driver adds a dynamic cpufreq policy governor.
148 The governor does a periodic polling and
149 changes frequency based on the CPU utilization.
150 The support for this governor depends on CPU capability to
151 do fast frequency switching (i.e, very low latency frequency
154 To compile this driver as a module, choose M here: the
155 module will be called cpufreq_ondemand.
157 For details, take a look at linux/Documentation/cpu-freq.
161 config CPU_FREQ_GOV_CONSERVATIVE
162 tristate "'conservative' cpufreq governor"
165 'conservative' - this driver is rather similar to the 'ondemand'
166 governor both in its source code and its purpose, the difference is
167 its optimisation for better suitability in a battery powered
168 environment. The frequency is gracefully increased and decreased
169 rather than jumping to 100% when speed is required.
171 If you have a desktop machine then you should really be considering
172 the 'ondemand' governor instead, however if you are using a laptop,
173 PDA or even an AMD64 based computer (due to the unacceptable
174 step-by-step latency issues between the minimum and maximum frequency
175 transitions in the CPU) you will probably want to use this governor.
177 To compile this driver as a module, choose M here: the
178 module will be called cpufreq_conservative.
180 For details, take a look at linux/Documentation/cpu-freq.