lwIP_ESPHost - using interrupt

[JAndrassy]

I attempt to make the ESPHost work with interrupt. There are two problems.

First problem is small. The DATA_READY pin is active HGH with esp_hosted. So we need a way to return from RawDev the state for interrupt.

Second problem is big. The semaphores don't work. It is a problem without the interrupt too, but with the interrupt version handlePackets doesn't run in async_context so there is no locking.
ethernet_arch_lwip_begin/end only guards code executed within async_context so using it elsewhere doesn't stop the code executing. It only blocks handlePackets if executed from the timer worker.

[earlephilhower]

For the 2nd problem, how is this different from the other Ethernet drivers? I'm not sure I understand it. When using IRQs the callback here does the processing which keeps the LWIP locked:

arduino-pico/libraries/lwIP_Ethernet/src/LwipIntfDev.h

Lines 431 to 438 in 77209a1

	template<class RawDev>
	void LwipIntfDev<RawDev>::_irq(void *param) {
	LwipIntfDev *d = static_cast<LwipIntfDev*>(param);
	ethernet_arch_lwip_begin();
	d->handlePackets();
	sys_check_timeouts();
	ethernet_arch_lwip_end();
	}

The only gotcha is the sendFrame call needs to mask off all Ethernet GPIO IRQs during processing, like here, to avoid Ethernet re-entrancy/deadlock:

arduino-pico/libraries/lwIP_w5100/src/utility/w5100.cpp

Lines 280 to 281 in 77209a1

	uint16_t Wiznet5100::sendFrame(const uint8_t* buf, uint16_t len) {
	ethernet_arch_lwip_gpio_mask(); // So we don't fire an IRQ and interrupt the send w/a receive!

...all the sendFrame procesing, finishing with...

arduino-pico/libraries/lwIP_w5100/src/utility/w5100.cpp

Lines 312 to 314 in 77209a1

	ethernet_arch_lwip_gpio_unmask();
	return len;
	}

Also, the LWIP mutex also disables GPIO IRQs while held so you don't end up with a packet coming in while other LWIP stuff is ongoing.

arduino-pico/cores/rp2040/lwip_wrap.cpp

Lines 43 to 46 in 77209a1

	LWIPMutex() {
	if (ethernet_arch_lwip_gpio_mask) {
	ethernet_arch_lwip_gpio_mask();
	}

arduino-pico/cores/rp2040/lwip_wrap.cpp

Lines 74 to 76 in 77209a1

	if (ethernet_arch_lwip_gpio_unmask) {
	ethernet_arch_lwip_gpio_unmask();
	}

[JAndrassy]

sorry, I forgot to check the other lwip_X for recent changes. I will try to use ethernet_arch_lwip_gpio_mask(); to block the IRQ while accessing the library from the main thread. I need to block access to ESPHost library not just from lwip, but from WiFi functions like MACAddress(mac) and RSSI() too.

[JAndrassy]

ok. ethernet_arch_lwip_gpio_mask() works. thank you

[JAndrassy]

Did you get any idea how much this helps with latency for, say, ping?

I didn't have much time. Today I continue the testing and I want to do a PR for the interrupt change state setting, which would be merged before this one.

[earlephilhower]

Thanks!