DVFS

This section introduces the DVFS driver APIs including terms and acronyms, supported features, details on how to use this driver, DVFS function groups, enums, structures and functions. More...

Overview

This section introduces the DVFS driver APIs including terms and acronyms, supported features, details on how to use this driver, DVFS function groups, enums, structures and functions.

Terms and acronyms

The following provides descriptions of the terms commonly used in the DVFS driver and how to use its various functions.

Terms	Details
DVFS	Dynamic Voltage and Frequency Scaling.
OPP	Operating Performance Point, a tuple of frequency and voltage. For more details, please refer to the section "Power modes" in MediaTek MT2523 datasheet.

How to use the driver

• The DVFS framework adjusts to the ideal CPU frequency at a suitable voltage level.
  • Step1: Call hal_dvfs_init() to initialize the DVFS module only once at system initialization.
  • Step2: Call hal_dvfs_get_cpu_frequency() to get the current CPU frequency.
  • Step3: Call hal_dvfs_get_cpu_frequency_list() to get the supported CPU frequencies.
  • Step4: Call hal_dvfs_target_cpu_frequency() to change the current CPU frequency.
  • Step5: Call hal_dvfs_get_cpu_frequency() to get the current CPU frequency.
  • Step6: Print out the frequencies obtained from Step2 and Step5 to identify the difference.
  • Sample code:

    uint32_t old_freq, cur_freq, list_num;
    const uint32_t *cpu_freq_list;
    
    hal_dvfs_init();
    old_freq = hal_dvfs_get_cpu_frequency();
    hal_dvfs_get_cpu_frequency_list(&cpu_freq_list, &list_num);
    hal_dvfs_target_cpu_frequency(cpu_freq_list[0], HAL_DVFS_FREQ_RELATION_L); // cpu_freq_list[0] is the highest and cpu_freq_list[list_num-1] is the lowest frequency.
    cur_freq = hal_dvfs_get_cpu_frequency();
    log_hal_info("old_freq=%d, cur_freq=%d\n", old_freq, cur_freq);

Functions
hal_dvfs_status_t	hal_dvfs_init (void)
	The function initializes the DVFS framework. More...
hal_dvfs_status_t	hal_dvfs_target_cpu_frequency (uint32_t target_freq, hal_dvfs_freq_relation_t relation)
	This function adjusts the CPU frequency to a suitable target frequency according to the passed-in relation. More...
uint32_t	hal_dvfs_get_cpu_frequency (void)
	This function gets the current CPU frequency. More...
hal_dvfs_status_t	hal_dvfs_get_cpu_frequency_list (const uint32_t **list, uint32_t *list_num)
	This function gets all adjustable CPU frequencies listed in the OPP table. More...

Modules
	Enum

Function Documentation

uint32_t hal_dvfs_get_cpu_frequency

(

void

)

This function gets the current CPU frequency.

Returns

The current CPU frequency is in kHz.

hal_dvfs_status_t hal_dvfs_get_cpu_frequency_list	(	const uint32_t **	list,
		uint32_t *	list_num
	)

This function gets all adjustable CPU frequencies listed in the OPP table.

Parameters

[out]	list	is a double pointer to the frequency table.
[out]	list_num	is a pointer to the number of the entries in the frequency table.

Returns

HAL_DVFS_STATUS_OK, if the operation completed successfully.
HAL_DVFS_STATUS_ERROR, if an error occurred during the operation..

hal_dvfs_status_t hal_dvfs_init

(

void

)

The function initializes the DVFS framework.

Returns

HAL_DVFS_STATUS_OK, if the initialization completed successfully.
HAL_DVFS_STATUS_ERROR, if an error occurred during the initialization.

hal_dvfs_status_t hal_dvfs_target_cpu_frequency	(	uint32_t	target_freq,
		hal_dvfs_freq_relation_t	relation
	)

This function adjusts the CPU frequency to a suitable target frequency according to the passed-in relation.

Parameters

[in]	target_freq	is the target frequency in kHz.
[in]	relation	is the relationship between the target frequency and the final frequency. HAL_DVFS_FREQ_RELATION_L, the lowest frequency at or above the target level. HAL_DVFS_FREQ_RELATION_H, the highest frequency below or at the target level. Example 1. hal_dvfs_target_cpu_frequency(103000, HAL_DVFS_FREQ_RELATION_L). The final CPU frequency is equal to or greater than 103MHz. Example 2. hal_dvfs_target_cpu_frequency(103000, HAL_DVFS_FREQ_RELATION_H). The final CPU frequency is equal to or less than 103MHz.

Returns

HAL_DVFS_STATUS_OK, if OK.
HAL_DVFS_STATUS_INVALID_PARAM, if the parameter value is invalid.
HAL_DVFS_STATUS_ERROR, if an error occurred.