dvfs_core.h File Reference

Structures and functions to change frequency at the scale of a CPU core. More...

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Data Structures
struct	dvfs_core
	Represents on core. More...

Functions
int	dvfs_core_open (dvfs_core **ppCore, unsigned int id, bool seq)
	Opens the Core context for the given core ID. More...
int	dvfs_core_close (dvfs_core *core)
	Closes properly an opened Core context. More...
int	dvfs_core_get_gov (const dvfs_core *core, char *buf, size_t buf_len)
	Sets the current DVFS governor on the given core to the given buffer. More...
int	dvfs_core_set_gov (const dvfs_core *core, const char *gov)
	Changes the governor on the given core. More...
int	dvfs_core_set_freq (const dvfs_core *core, unsigned int freq)
	Sets the frequency for the given core. More...
int	dvfs_core_get_current_freq (const dvfs_core *core, unsigned int *pFreq)
	Gets the frequency currently set for the core. More...
int	dvfs_core_get_freq (const dvfs_core *core, unsigned int *pFreq, unsigned int freq_id)
	Gets the frequency currently set for the core. More...
int	dvfs_core_get_nb_freqs (const dvfs_core *core, unsigned int *pNbFreq)
	Gets the number of frequencies available for the core. More...
int	dvfs_core_get_id (const dvfs_core *core, unsigned int *pID)
	Gets the ID of the DVFS core. More...

Detailed Description

Structures and functions to change frequency at the scale of a CPU core.

Function Documentation

int dvfs_core_close

(

dvfs_core *

core

)

Closes properly an opened Core context.

Sets back the governor that was in place when opening the context.

Parameters

core	The core to close.

Returns

Return values

DVFS_SUCCESS	if everything goes right.
DVFS_ERROR_INVALID_ARG	if core is NULL.

int dvfs_core_get_current_freq	(	const dvfs_core *	core,
		unsigned int *	pFreq
	)

Gets the frequency currently set for the core.

Warning, this is not necessarily the frequency currently active for the core as other cores in the same unit may have requested a different frequency. In order to determine the frequency actually set for the core, use instead dvfs_unit_get_freq().

Parameters

core	The CPU core.
pFreq	The frequency currently set.

Returns

Return values

DVFS_SUCCESS	if everything goes right.
DVFS_ERROR_INVALID_ARG	if core or buf are NULL.
DVFS_ERROR_FILE_ERROR	operation on file failed (you can check errno for more details).

See also

dvfs_unit_get_freq()

int dvfs_core_get_freq	(	const dvfs_core *	core,
		unsigned int *	pFreq,
		unsigned int	freq_id
	)

Gets the frequency currently set for the core.

Parameters

core	The CPU core.
pFreq	The frequency currentlu set
freq_id	The id of the frequency with respect to the order in the freqs internal array

Returns

Return values

DVFS_SUCCESS	if everything goes right.
DVFS_ERROR_INVALID_ARG	if core or pFreq are NULL.
DVFS_ERROR_INVALID_FREQ_ID	the id passed is not valid

int dvfs_core_get_gov	(	const dvfs_core *	core,
		char *	buf,
		size_t	buf_len
	)

Sets the current DVFS governor on the given core to the given buffer.

Parameters

core	The core on which the governor has to be set.
buf	The pointer to the buffer which will be set to the governor string value
buf_len	The size of the buffer

Returns

Return values

DVFS_SUCCESS	if everything goes right.
DVFS_ERROR_INVALID_ARG	if core or buf are NULL.
DVFS_ERROR_BUFFER_TOO_SHORT	if the buffer for the path to the governor file is too short
DVFS_ERROR_FILE_ERROR	operation on file failed (you can check errno for more details).

int dvfs_core_get_id	(	const dvfs_core *	core,
		unsigned int *	pID
	)

Gets the ID of the DVFS core.

Parameters

core	The CPU core.
pID	Will be filled with the ID

Returns

Return values

DVFS_SUCCESS	if everything goes right.
DVFS_ERROR_INVALID_ARG	if core or pNbFreq are NULL.

int dvfs_core_get_nb_freqs	(	const dvfs_core *	core,
		unsigned int *	pNbFreq
	)

Gets the number of frequencies available for the core.

Parameters

core	The CPU core.
pNbFreq	The number of frequencies available for the core

Returns

Return values

DVFS_SUCCESS	if everything goes right.
DVFS_ERROR_INVALID_ARG	if core or pNbFreq are NULL.

int dvfs_core_open	(	dvfs_core **	ppCore,
		unsigned int	id,
		bool	seq
	)

Opens the Core context for the given core ID.

The dvfs_core is valid even if the semaphore failed. The frequency transitions will not be seqeuntialized.

Parameters

ppCore	the instanciated Core context for this core. May return NULL in case of error. The error cases are often related to file opening (such as permission denied). In such cases errno is set appropriately.
id	The id of the core to control.
seq	True when the frequency transitions must be sequentialized.

Returns

Return values

DVFS_SUCCESS	if everything goes right.
DVFS_ERROR_INVALID_ARG	if ppUnit or cores are NULL.
DVFS_ERROR_MEM_ALLOC_FAILED	if memory allocation failed.

See also

dvfs_core_close()

int dvfs_core_set_freq	(	const dvfs_core *	core,
		unsigned int	freq
	)

Sets the frequency for the given core.

Assumes that the "userspace" governor has been set, result is unknown otherwise.

Parameters

core	The related core.
freq	The frequency to set.

Returns

Return values

DVFS_SUCCESS	if everything goes right.
DVFS_ERROR_INVALID_ARG	if core or buf are NULL.
DVFS_ERROR_SET_FREQ_FILE	frequency file not operational.
DVFS_ERROR_FILE_ERROR	operation on file failed (you can check errno for more details).

int dvfs_core_set_gov	(	const dvfs_core *	core,
		const char *	gov
	)

Changes the governor on the given core.

Parameters

core	The core on which the governor has to be set.
gov	The governor to set.

Returns

Return values

DVFS_SUCCESS	if everything goes right.
DVFS_ERROR_INVALID_ARG	if core or buf are NULL.
DVFS_ERROR_BUFFER_TOO_SHORT	if the buffer for the path to the governor file is too short.
DVFS_ERROR_FILE_ERROR	operation on file failed (you can check errno for more details).