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 tristate "CPU frequency translation statistics"
26 This driver exports CPU frequency statistics information through sysfs
29 To compile this driver as a module, choose M here: the
30 module will be called cpufreq_stats.
34 config CPU_FREQ_STAT_DETAILS
35 bool "CPU frequency translation statistics details"
36 depends on CPU_FREQ_STAT
38 This will show detail CPU frequency translation table in sysfs file
44 prompt "Default CPUFreq governor"
45 default CPU_FREQ_DEFAULT_GOV_USERSPACE if CPU_FREQ_SA1100 || CPU_FREQ_SA1110
46 default CPU_FREQ_DEFAULT_GOV_PERFORMANCE
48 This option sets which CPUFreq governor shall be loaded at
49 startup. If in doubt, select 'performance'.
51 config CPU_FREQ_DEFAULT_GOV_PERFORMANCE
53 select CPU_FREQ_GOV_PERFORMANCE
55 Use the CPUFreq governor 'performance' as default. This sets
56 the frequency statically to the highest frequency supported by
59 config CPU_FREQ_DEFAULT_GOV_POWERSAVE
62 select CPU_FREQ_GOV_POWERSAVE
64 Use the CPUFreq governor 'powersave' as default. This sets
65 the frequency statically to the lowest frequency supported by
68 config CPU_FREQ_DEFAULT_GOV_USERSPACE
70 select CPU_FREQ_GOV_USERSPACE
72 Use the CPUFreq governor 'userspace' as default. This allows
73 you to set the CPU frequency manually or when a userspace
74 program shall be able to set the CPU dynamically without having
75 to enable the userspace governor manually.
77 config CPU_FREQ_DEFAULT_GOV_ONDEMAND
79 select CPU_FREQ_GOV_ONDEMAND
80 select CPU_FREQ_GOV_PERFORMANCE
82 Use the CPUFreq governor 'ondemand' as default. This allows
83 you to get a full dynamic frequency capable system by simply
84 loading your cpufreq low-level hardware driver.
85 Be aware that not all cpufreq drivers support the ondemand
86 governor. If unsure have a look at the help section of the
87 driver. Fallback governor will be the performance governor.
89 config CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
91 select CPU_FREQ_GOV_CONSERVATIVE
92 select CPU_FREQ_GOV_PERFORMANCE
94 Use the CPUFreq governor 'conservative' as default. This allows
95 you to get a full dynamic frequency capable system by simply
96 loading your cpufreq low-level hardware driver.
97 Be aware that not all cpufreq drivers support the conservative
98 governor. If unsure have a look at the help section of the
99 driver. Fallback governor will be the performance governor.
102 config CPU_FREQ_GOV_PERFORMANCE
103 tristate "'performance' governor"
105 This cpufreq governor sets the frequency statically to the
106 highest available CPU frequency.
108 To compile this driver as a module, choose M here: the
109 module will be called cpufreq_performance.
113 config CPU_FREQ_GOV_POWERSAVE
114 tristate "'powersave' governor"
116 This cpufreq governor sets the frequency statically to the
117 lowest available CPU frequency.
119 To compile this driver as a module, choose M here: the
120 module will be called cpufreq_powersave.
124 config CPU_FREQ_GOV_USERSPACE
125 tristate "'userspace' governor for userspace frequency scaling"
127 Enable this cpufreq governor when you either want to set the
128 CPU frequency manually or when a userspace program shall
129 be able to set the CPU dynamically, like on LART
130 <http://www.lartmaker.nl/>.
132 To compile this driver as a module, choose M here: the
133 module will be called cpufreq_userspace.
135 For details, take a look at <file:Documentation/cpu-freq/>.
139 config CPU_FREQ_GOV_ONDEMAND
140 tristate "'ondemand' cpufreq policy governor"
141 select CPU_FREQ_TABLE
143 'ondemand' - This driver adds a dynamic cpufreq policy governor.
144 The governor does a periodic polling and
145 changes frequency based on the CPU utilization.
146 The support for this governor depends on CPU capability to
147 do fast frequency switching (i.e, very low latency frequency
150 To compile this driver as a module, choose M here: the
151 module will be called cpufreq_ondemand.
153 For details, take a look at linux/Documentation/cpu-freq.
157 config CPU_FREQ_GOV_CONSERVATIVE
158 tristate "'conservative' cpufreq governor"
161 'conservative' - this driver is rather similar to the 'ondemand'
162 governor both in its source code and its purpose, the difference is
163 its optimisation for better suitability in a battery powered
164 environment. The frequency is gracefully increased and decreased
165 rather than jumping to 100% when speed is required.
167 If you have a desktop machine then you should really be considering
168 the 'ondemand' governor instead, however if you are using a laptop,
169 PDA or even an AMD64 based computer (due to the unacceptable
170 step-by-step latency issues between the minimum and maximum frequency
171 transitions in the CPU) you will probably want to use this governor.
173 To compile this driver as a module, choose M here: the
174 module will be called cpufreq_conservative.
176 For details, take a look at linux/Documentation/cpu-freq.