FLL Runtime

group FLL Runtime

Host-side FLL parameter calculation and frequency switching utilities.

These functions operate above the low-level FLL driver (drivers_fll) and handle the higher-level tasks: computing multiplier/divider values, switching both the SOC and cluster FLLs in concert, and reconfiguring the UART baud rate after a frequency change.

Functions

int calculate_fll_params(uint32_t target_freq, uint32_t rtc_freq, uint32_t *mult, uint32_t *div)

Calculate FLL parameters for a target frequency.

Parameters:

  • target_freq – Target frequency in Hz

  • rtc_freq – RTC frequency in Hz

  • mult – Output: FLL multiplier

  • div – Output: FLL divider (power of 2)

Returns:

0 on success, -1 on error

uint32_t configure_fll(uint32_t target_freq, uint32_t rtc_freq)

Configure FLLs to target frequency and reconfigure UART.

Parameters:

  • target_freq – Target frequency in Hz

  • rtc_freq – RTC frequency in Hz

Returns:

Actual configured frequency in Hz, or 0 on error

uint32_t restore_default_freq(uint32_t rtc_freq)

Restore the core frequency to its reset value and reconfigure UART.

Measures the actual reset-domain clock frequency using the CLINT as a reference, then reopens the UART with the measured frequency so that the baud rate remains correct after an FLL is switched off.

Parameters:

rtc_freq – Reference RTC frequency in Hz (used as timing reference).

Returns:

Measured core frequency in Hz, or 0 on error.