stm32: clock-control: Remove usage of SystemCoreClock

[erwango]

Is your enhancement proposal related to a problem? Please describe.
STM32 clock control driver is using variable SystemCoreClock to hold core clock frequency.
It was used in order to avoid usage of constant symbol CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC
Reason was cpu freq setting is usually done in 2 step with a default value at boot and the configured value set up at clock_control driver init.

Requires:

• removing direct usage of CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC (Decouple timers from system clock #16958)
• move clock configuration from device tree (stm32: Move clock configuration to device tree #17745)
• get sys_clock_hw_cycles_per_sec to return updated clock through implementation of CONFIG_TIMER_READS_ITS_FREQUENCY_AT_RUNTIME for STM32 (or similar)

[ikerperezdelpalomar]

Hi, I am willing to learn about Zephyr so I considered that this might be a nice issue that start working from. Is it ok if I try to solve it?

[galak]

Hi, I am willing to get learn about Zephyr so I considered that this might be a nice issue that start working from. Is it ok if I try to solve it?

@ikerperezdelpalomar are you familiar with devicetree?

[ikerperezdelpalomar]

Hi, I am willing to get learn about Zephyr so I considered that this might be a nice issue that start working from. Is it ok if I try to solve it?

@ikerperezdelpalomar are you familiar with devicetree?

A bit, I worked in project that involved devicetree 1 year ago.

[erwango]

Closing as I'm not certain this is the way to go anymore.
At least, this is not a goal by itself anymore