1config CPU_FREQ 2 bool "CPU Frequency scaling" 3 help 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. 7 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. 11 12 For details, take a look at <file:Documentation/cpu-freq>. 13 14 If in doubt, say N. 15 16if CPU_FREQ 17 18config CPU_FREQ_TABLE 19 tristate 20 21config CPU_FREQ_DEBUG 22 bool "Enable CPUfreq debugging" 23 help 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 27 cpufreq.debug=<value> 28 29 To get <value>, add 30 1 to activate CPUfreq core debugging, 31 2 to activate CPUfreq drivers debugging, and 32 4 to activate CPUfreq governor debugging 33 34config CPU_FREQ_STAT 35 tristate "CPU frequency translation statistics" 36 select CPU_FREQ_TABLE 37 default y 38 help 39 This driver exports CPU frequency statistics information through sysfs 40 file system 41 42config CPU_FREQ_STAT_DETAILS 43 bool "CPU frequency translation statistics details" 44 depends on CPU_FREQ_STAT 45 help 46 This will show detail CPU frequency translation table in sysfs file 47 system 48 49# Note that it is not currently possible to set the other governors (such as ondemand) 50# as the default, since if they fail to initialise, cpufreq will be 51# left in an undefined state. 52 53choice 54 prompt "Default CPUFreq governor" 55 default CPU_FREQ_DEFAULT_GOV_USERSPACE if CPU_FREQ_SA1100 || CPU_FREQ_SA1110 56 default CPU_FREQ_DEFAULT_GOV_PERFORMANCE 57 help 58 This option sets which CPUFreq governor shall be loaded at 59 startup. If in doubt, select 'performance'. 60 61config CPU_FREQ_DEFAULT_GOV_PERFORMANCE 62 bool "performance" 63 select CPU_FREQ_GOV_PERFORMANCE 64 help 65 Use the CPUFreq governor 'performance' as default. This sets 66 the frequency statically to the highest frequency supported by 67 the CPU. 68 69config CPU_FREQ_DEFAULT_GOV_USERSPACE 70 bool "userspace" 71 select CPU_FREQ_GOV_USERSPACE 72 help 73 Use the CPUFreq governor 'userspace' as default. This allows 74 you to set the CPU frequency manually or when an userspace 75 program shall be able to set the CPU dynamically without having 76 to enable the userspace governor manually. 77 78endchoice 79 80config CPU_FREQ_GOV_PERFORMANCE 81 tristate "'performance' governor" 82 help 83 This cpufreq governor sets the frequency statically to the 84 highest available CPU frequency. 85 86 If in doubt, say Y. 87 88config CPU_FREQ_GOV_POWERSAVE 89 tristate "'powersave' governor" 90 help 91 This cpufreq governor sets the frequency statically to the 92 lowest available CPU frequency. 93 94 If in doubt, say Y. 95 96config CPU_FREQ_GOV_USERSPACE 97 tristate "'userspace' governor for userspace frequency scaling" 98 help 99 Enable this cpufreq governor when you either want to set the 100 CPU frequency manually or when an userspace program shall 101 be able to set the CPU dynamically, like on LART 102 <http://www.lartmaker.nl/>. 103 104 For details, take a look at <file:Documentation/cpu-freq/>. 105 106 If in doubt, say Y. 107 108config CPU_FREQ_GOV_ONDEMAND 109 tristate "'ondemand' cpufreq policy governor" 110 select CPU_FREQ_TABLE 111 help 112 'ondemand' - This driver adds a dynamic cpufreq policy governor. 113 The governor does a periodic polling and 114 changes frequency based on the CPU utilization. 115 The support for this governor depends on CPU capability to 116 do fast frequency switching (i.e, very low latency frequency 117 transitions). 118 119 For details, take a look at linux/Documentation/cpu-freq. 120 121 If in doubt, say N. 122 123config CPU_FREQ_GOV_CONSERVATIVE 124 tristate "'conservative' cpufreq governor" 125 depends on CPU_FREQ 126 help 127 'conservative' - this driver is rather similar to the 'ondemand' 128 governor both in its source code and its purpose, the difference is 129 its optimisation for better suitability in a battery powered 130 environment. The frequency is gracefully increased and decreased 131 rather than jumping to 100% when speed is required. 132 133 If you have a desktop machine then you should really be considering 134 the 'ondemand' governor instead, however if you are using a laptop, 135 PDA or even an AMD64 based computer (due to the unacceptable 136 step-by-step latency issues between the minimum and maximum frequency 137 transitions in the CPU) you will probably want to use this governor. 138 139 For details, take a look at linux/Documentation/cpu-freq. 140 141 If in doubt, say N. 142 143endif # CPU_FREQ 144