esp32: Consider CPU frequency constraints when Wi-Fi/BT is enabled

[garywill]

Port, board and/or hardware

esp32

MicroPython version

v1.26.1

Reproduction

I’ve tested this myself:

1. Turn on Wi-Fi

2. machine.freq(40_000_000)
   MPY freezes

3. freq(40_000_000) first

4. wlan.active(True)
   MPY freezes

Expected behaviour

Espressif’s docs do say that APB clock must be ≥80 MHz when wireless is on, and APB = CPU freq when it’s under 80 MHz

Observed behaviour

MPY freezes when cpu freq not compatitable with wireless module.

I think it stucks here:

micropython/ports/esp32/modmachine.c

Lines 128 to 130 in 27544a2

	while (esp_rom_get_cpu_ticks_per_us() != freq) {
	vTaskDelay(1);
	}

micropython/ports/esp32/network_wlan.c

Lines 291 to 294 in 27544a2

	// Wait for the interface to be in the correct state.
	while (self->active != active) {
	MICROPY_EVENT_POLL_HOOK;
	}

Additional Information

Would it be possible to add a safeguard in MPY? For example:
If Wi-Fi or BLE is active, set a min allowed freq (raise an exception or warn if user tries to go lower)
When CPU freq already low, don't allow to enable wifi

Some tips from web:

CPU Frequency	Wi-Fi (STA/AP)	BLE (Low Energy)	Bluetooth Classic (A2DP, SPP, etc.)
≥ 160 MHz	✅ Stable	✅ Stable	✅ Recommended / Stable
80 – 159 MHz	✅ Generally OK	✅ Generally OK	⚠️ May be unstable (not recommended)
< 80 MHz	❌ Unreliable / Hangs	❌ Unreliable / Hangs	❌ Likely to fail

Code of Conduct

Yes, I agree

[Josverl]

I think documenting such limits makes more sense that adding code for every possible incorrect combination.