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_POWERSAVE
75 select CPU_FREQ_GOV_POWERSAVE
77 Use the CPUFreq governor 'powersave' as default. This sets
78 the frequency statically to the lowest frequency supported by
81 config CPU_FREQ_DEFAULT_GOV_USERSPACE
83 select CPU_FREQ_GOV_USERSPACE
85 Use the CPUFreq governor 'userspace' as default. This allows
86 you to set the CPU frequency manually or when an userspace
87 program shall be able to set the CPU dynamically without having
88 to enable the userspace governor manually.
90 config CPU_FREQ_DEFAULT_GOV_ONDEMAND
92 select CPU_FREQ_GOV_ONDEMAND
93 select CPU_FREQ_GOV_PERFORMANCE
95 Use the CPUFreq governor 'ondemand' as default. This allows
96 you to get a full dynamic frequency capable system by simply
97 loading your cpufreq low-level hardware driver.
98 Be aware that not all cpufreq drivers support the ondemand
99 governor. If unsure have a look at the help section of the
100 driver. Fallback governor will be the performance governor.
102 config CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
104 select CPU_FREQ_GOV_CONSERVATIVE
105 select CPU_FREQ_GOV_PERFORMANCE
107 Use the CPUFreq governor 'conservative' as default. This allows
108 you to get a full dynamic frequency capable system by simply
109 loading your cpufreq low-level hardware driver.
110 Be aware that not all cpufreq drivers support the conservative
111 governor. If unsure have a look at the help section of the
112 driver. Fallback governor will be the performance governor.
115 config CPU_FREQ_GOV_PERFORMANCE
116 tristate "'performance' governor"
118 This cpufreq governor sets the frequency statically to the
119 highest available CPU frequency.
121 To compile this driver as a module, choose M here: the
122 module will be called cpufreq_performance.
126 config CPU_FREQ_GOV_POWERSAVE
127 tristate "'powersave' governor"
129 This cpufreq governor sets the frequency statically to the
130 lowest available CPU frequency.
132 To compile this driver as a module, choose M here: the
133 module will be called cpufreq_powersave.
137 config CPU_FREQ_GOV_USERSPACE
138 tristate "'userspace' governor for userspace frequency scaling"
140 Enable this cpufreq governor when you either want to set the
141 CPU frequency manually or when an userspace program shall
142 be able to set the CPU dynamically, like on LART
143 <http://www.lartmaker.nl/>.
145 To compile this driver as a module, choose M here: the
146 module will be called cpufreq_userspace.
148 For details, take a look at <file:Documentation/cpu-freq/>.
152 config CPU_FREQ_GOV_ONDEMAND
153 tristate "'ondemand' cpufreq policy governor"
154 select CPU_FREQ_TABLE
156 'ondemand' - This driver adds a dynamic cpufreq policy governor.
157 The governor does a periodic polling and
158 changes frequency based on the CPU utilization.
159 The support for this governor depends on CPU capability to
160 do fast frequency switching (i.e, very low latency frequency
163 To compile this driver as a module, choose M here: the
164 module will be called cpufreq_ondemand.
166 For details, take a look at linux/Documentation/cpu-freq.
170 config CPU_FREQ_GOV_CONSERVATIVE
171 tristate "'conservative' cpufreq governor"
174 'conservative' - this driver is rather similar to the 'ondemand'
175 governor both in its source code and its purpose, the difference is
176 its optimisation for better suitability in a battery powered
177 environment. The frequency is gracefully increased and decreased
178 rather than jumping to 100% when speed is required.
180 If you have a desktop machine then you should really be considering
181 the 'ondemand' governor instead, however if you are using a laptop,
182 PDA or even an AMD64 based computer (due to the unacceptable
183 step-by-step latency issues between the minimum and maximum frequency
184 transitions in the CPU) you will probably want to use this governor.
186 To compile this driver as a module, choose M here: the
187 module will be called cpufreq_conservative.
189 For details, take a look at linux/Documentation/cpu-freq.