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32 .Nd CPU frequency control framework
38 .Fn cpufreq_levels "device_t dev" "struct cf_level *levels" "int *count"
40 .Fn cpufreq_set "device_t dev" "const struct cf_level *level" "int priority"
42 .Fn cpufreq_get "device_t dev" "struct cf_level *level"
44 .Fo cpufreq_drv_settings
46 .Fa "struct cf_setting *sets"
50 .Fn cpufreq_drv_type "device_t dev" "int *type"
52 .Fn cpufreq_drv_set "device_t dev" "const struct cf_setting *set"
54 .Fn cpufreq_drv_get "device_t dev" "struct cf_setting *set"
58 driver provides a unified kernel and user interface to CPU frequency
60 It combines multiple drivers offering different settings into a single
61 interface of all possible levels.
62 Users can access this interface directly via
65 .Pa /etc/rc.d/power_profile
66 that it should switch settings when the AC line state changes via
69 These settings may be overridden by kernel drivers requesting alternate
71 If this occurs, the original values will be restored once the condition
72 has passed (e.g., the system has cooled sufficiently).
73 If a sysctl cannot be set due to an override condition, it will return
75 .Bl -tag -width indent
76 .It Va dev.cpu.%d.freq
77 Current active CPU frequency in MHz.
78 .It Va dev.cpu.%d.freq_levels
79 Currently available levels for the CPU (frequency/power usage).
80 Values are in units of MHz and milliwatts.
81 .It Va dev.DEVICE.%d.freq_settings
82 Currently available settings for the driver (frequency/power usage).
83 Values are in units of MHz and milliwatts.
84 This is helpful for understanding which settings are offered by which
85 driver for debugging purposes.
86 .It Va debug.cpufreq.lowest
87 Lowest CPU frequency in MHz to offer to users.
88 This setting is also accessible via a tunable with the same name.
89 This can be used to disable very low levels that may be unusable on
91 .It Va debug.cpufreq.verbose
92 Print verbose messages.
93 This setting is also accessible via a tunable with the same name.
96 The following device drivers offer absolute frequency control via the
99 Usually, only one of these can be active at a time.
101 .Bl -tag -compact -width ".Pa acpi_perf"
103 ACPI CPU performance states
105 Intel Enhanced SpeedStep
107 Intel SpeedStep for ICH
109 AMD PowerNow!\& for K7 and K8
111 Intel SMI-based SpeedStep for PIIX4
114 The following device drivers offer relative frequency control and
115 have an additive effect:
117 .Bl -tag -compact -width ".Pa acpi_throttle"
121 Pentium 4 Thermal Control Circuitry
124 Kernel components can query and set CPU frequencies through the
127 This involves obtaining a
131 to get the currently available frequency levels,
132 checking the current level with
134 and setting a new one from the list with
136 Each level may actually reference more than one
138 driver but kernel components do not need to be aware of this.
142 .Vt "struct cf_level"
143 provides a summary of the frequency and power for this level.
144 Unknown or irrelevant values are set to
145 .Dv CPUFREQ_VAL_UNKNOWN .
151 device and an empty array of
155 value should be set to the number of levels available and after the
156 function completes, will be set to the actual number of levels returned.
157 If there are more levels than
159 will allow, it should return
164 method takes a pointer to space to store a
166 After successful completion, the output will be the current active level
167 and is equal to one of the levels returned by
172 method takes a pointer a
174 and attempts to activate it.
178 .Dv CPUFREQ_PRIO_KERN )
181 whether to override previous settings while activating this level.
184 is higher than the current active level, that level will be saved and
185 overridden with the new level.
186 If a level is already saved, the new level is set without overwriting
187 the older saved level.
193 the saved level will be restored.
194 If there is no saved level,
200 is lower than the current active level's priority, this method returns
203 Kernel drivers offering hardware-specific CPU frequency control export
204 their individual settings through the
207 This involves implementing these methods:
208 .Fn cpufreq_drv_settings ,
209 .Fn cpufreq_drv_type ,
210 .Fn cpufreq_drv_set ,
212 .Fn cpufreq_drv_get .
213 Additionally, the driver must attach a device as a child of a CPU
214 device so that these methods can be called by the
219 .Fn cpufreq_drv_settings
220 method returns an array of currently available settings, each of type
221 .Vt "struct cf_setting" .
222 The driver should set unknown or irrelevant values to
223 .Dv CPUFREQ_VAL_UNKNOWN .
224 All the following elements for each setting should be returned:
227 int freq; /* CPU clock in Mhz or 100ths of a percent. */
228 int volts; /* Voltage in mV. */
229 int power; /* Power consumed in mW. */
230 int lat; /* Transition latency in us. */
231 device_t dev; /* Driver providing this setting. */
235 On entry to this method,
237 contains the number of settings that can be returned.
238 On successful completion, the driver sets it to the actual number of
240 If the driver offers more settings than
242 will allow, it should return
247 method indicates the type of settings it offers, either
248 .Dv CPUFREQ_TYPE_ABSOLUTE
250 .Dv CPUFREQ_TYPE_RELATIVE .
251 Additionally, the driver may set the
252 .Dv CPUFREQ_FLAG_INFO_ONLY
253 flag if the settings it provides are information for other drivers only
254 and cannot be passed to
260 method takes a driver setting and makes it active.
261 If the setting is invalid or not currently available, it should return
266 method returns the currently-active driver setting.
268 .Vt "struct cf_setting"
269 returned must be valid for passing to
270 .Fn cpufreq_drv_set ,
271 including all elements being filled out correctly.
272 If the driver cannot infer the current setting
273 (even by estimating it with
274 .Fn cpu_est_clockrate )
275 then it should set all elements to
276 .Dv CPUFREQ_VAL_UNKNOWN .
287 The following drivers have not yet been converted to the
292 Notification of CPU and bus frequency changes is not implemented yet.
294 When multiple CPUs offer frequency control, they cannot be set to different
295 levels and must all offer the same frequency settings.