drivers: clock_control: Nordic nRF54L15 HFCLK can't be activated with `clock_control_on()` anymore

[GardeningStevie]

Describe the bug

Since PR #86354, my application can't activate the HF clock source (external HF crystal) with clock_control_on() when the crystal is physically off. The error code -EPERM (-1) is returned.

Actually, the internal flags state is set to 2 which means CLOCK_CONTROL_STATUS_ON. That's the reason why clock_control_on() returns -1. However, the clock control state is wrong. I have checked the CLOCK register and crystal itself. It is off.

The reason for CLOCK_CONTROL_STATUS_ON is the call of clkstarted_handle() here

zephyr/drivers/clock_control/clock_control_nrf.c

Lines 703 to 706 in 0f66e9c

	#if NRF_CLOCK_HAS_XO_TUNE
	case NRFX_CLOCK_EVT_XO_TUNED:
	clkstarted_handle(dev, CLOCK_CONTROL_NRF_TYPE_HFCLK);
	break;

clkstarted_handle() enforces that the internal flags state is set to CLOCK_CONTROL_STATUS_ON. Somehow that state is never reset to CLOCK_CONTROL_STATUS_OFF.

I could "fix" this issue when I replaced the current implementation with the old one that checked if the current state is CLOCK_CONTROL_STATUS_STARTING which make sense IMHO.

zephyr/drivers/clock_control/clock_control_nrf.c

Lines 719 to 730 in c326bf6

	{
	struct nrf_clock_control_sub_data *data =
	get_sub_data(dev, CLOCK_CONTROL_NRF_TYPE_HFCLK);
	/* Check needed due to anomaly 201:
	* HFCLKSTARTED may be generated twice.
	*/
	if (GET_STATUS(data->flags) == CLOCK_CONTROL_STATUS_STARTING) {
	clkstarted_handle(dev, CLOCK_CONTROL_NRF_TYPE_HFCLK);
	}
	break;

I didn't check if the clock is handled really correctly with this work-around. I have just noticed that with this fix clock_control_on() and clock_control_off() work as expected.

I use these feature for crystals frequency checking in production. Unable to enable the crystal permanently is a release blocker for me.

Regression

• This is a regression.

Steps to reproduce

Not entirely sure what is really required to reproduce. I have ...

1. Bluetooth application in advertising mode
2. Stop BT advertising
3. Call clock_control_on(CLOCK_DEVICE, CLOCK_CONTROL_NRF_SUBSYS_HF);

Relevant log output

Impact

Showstopper – Prevents release or major functionality; system unusable.

Environment

• Zephyr 4.2
• Nordic nRF54L15

Additional Context

No response

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