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Re: A simple cpufreq(9)
On Mon, Sep 26, 2011 at 10:03:06AM -0500, David Young wrote:
> Instead, provide an API routine for finding out the number of states
> (nstates) and a routine for selecting a state [0, nstates - 1].
The code is ready and it is available in . However, I can not complete it
because when trying to upgrade, I encounter PR kern/45361.
All existing drivers were converted, expect ichlpcib(4) and piixpcib(4)
(for these, I think first the SpeedStep should be splitted as a child
device of the bridge).
This breaks COMPAT_50 of cpuctl(8). How to handle that? #ifdefs?
* * *
CPUFREQ(9) NetBSD Kernel Developer's Manual CPUFREQ(9)
cpufreq, cpufreq_register, cpufreq_deregister, cpufreq_suspend,
cpufreq_resume, cpufreq_get, cpufreq_set, cpufreq_set_all -- interface
for CPU frequency scaling
cpufreq_register(struct cpufreq_if *cif);
cpufreq_suspend(struct cpu_info *ci);
cpufreq_resume(struct cpu_info *ci);
cpufreq_get(struct cpu_info *ci, uint16_t *freq);
cpufreq_get_if(struct cpufreq_if *cif);
cpufreq_set(struct cpu_info *ci, uint16_t freq);
The machine-independent cpufreq interface provides a framework for CPU
frequency scaling done by a machine-dependent backend implementation.
User space control is available via cpuctl(8).
The cpufreq interface is a per-CPU framework. It is implicitly assumed
that the frequency can be set independently for all processors in the
system. However, cpufreq does not imply any restrictions upon whether
this information is utilized by the actual machine-dependent
tion. It is possible to use cpufreq with frequency scaling implemented
via pci(4). In addition, it assumed that the available frequency
are shared uniformly by all processors in the system, even when it is
possible to control the frequency of individual processors.
It should be noted that the cpufreq interface is generally stateless.
This implies for instance that possible caching should be done in the
machine-dependent backend. The cpufreq_suspend() and cpufreq_resume()
functions are exceptions. These can be integrated with pmf(9).
The cpufreq_register() function initializes the interface by
associating a machine-dependent backend with the framework.
Only one backend can be registered. Upon successful completion,
cpufreq_register() returns 0 and sets the frequency to the maxi-
mum available level.
The following elements in the cpufreq_if structure should be
filled prior to the call:
struct cpufreq_state state[CPUFREQ_STATE_MAX];
· The name of the backend is required.
· The cpufreq_state structure conveys descriptive information
about the frequency states. The following fields can be
used for the registration:
From these freq (the clock frequency in MHz) is mandatory,
whereas the optional power can be filled to describe the
power consumption (in mW) of each state.
· The state_count defines the number of states that the back-
end has filled in the state array.
· The mp boolean should be set to false if it is known that
the backend can not handle per-CPU frequency states; changes
should always be propagated to all processors in the system.
· The cookie field is an opaque pointer passed to the backend
when cpufreq_get() cpufreq_set(), or cpufreq_set_all() is
· The get_freq and set_freq are function pointers that should
be associated with the machine-dependent functions to get
and set a frequency, respectively. The xcfunc_t type con-
forms to xcall(9). When the function pointers are invoked
by cpufreq, the first parameter is always the cookie and
the second parameter is the frequency, defined as uint16_t *.
Deregisters any possible backend in use.
The cpufreq_suspend() can be called when the processor suspends.
The function saves the current frequency of ci and sets the min-
imum available frequency.
Resumes the frequency of ci that was used before suspend.
The cpufreq_get() function obtains the current frequency level
of the processor pointed by ci in the parameter freq.
Upon successful completion, cpufreq_get_if() returns 0 and fills
cif with the information of the currently used backend.
The cpufreq_set() function sets the frequency of ci to freq.
Sets freq for all processors in the system.
The three functions cpufreq_get(), cpufreq_set(), and cpufreq_set_all()
guarantee that the call will be made in curcpu(9). The interface holds
cpu_lock while calling the functions. This, and the use of xcall(9),
implies that no memory can be allocated in the backend during the calls.
The cpufreq interface is implemented within sys/kern/subr_cpufreq.c.
cpuctl(8), pmf(9), xcall(9)
The cpufreq interface first appeared in NetBSD 6.0.
The interface does not support different ``governors'' and policies.
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