Interrupt service routines are not placed in IRAM

[hajosc]

Board

Board-independent

Device Description

Valid for all Tensilica

Hardware Configuration

Any GPIO being interrupt-capable

Version

latest stable Release (if not listed below)

Type

Bug

IDE Name

Arduino-cli

Operating System

Linux

Flash frequency

80M

PSRAM enabled

no

Upload speed

921600

Description

Although Tensilica explicitly recommends putting ISRs into IRAM, GPIO-hal appears to put the underlying pin ISR into Flash. This leads to a lot of lost interrupts if Flash write is used, it appears that hundreds of msecs seem to be the order of magnitude.
I think this should at least be clearly mentioned and the related CONFIG_ARDUINO_ISR_IRAM be explained or another functionality be provided for the user to select behavior.

Sketch

Just look at the .MAP file, user ISRs are in flash.

Debug Message

Again, the memory map is enough as proof.

Other Steps to Reproduce

No response

I have checked existing issues, online documentation and the Troubleshooting Guide

• I confirm I have checked existing issues, online documentation and Troubleshooting guide.

[hajosc]

In #8802 the OP observes this problem, #8802 (comment) states the fact...

[me-no-dev]

Chips have limited IRAM size. If we put interrupts in IRAM, many projects will fail to compile, because IRAM overflow. There are more reasons why IRAM interrupts are a problem, like the fact that everything that gets called inside IRAM interrupt MUST be also in IRAM or Flash will still get accessed and if not expected, that can cause a whole lot of other problems. We have decided interrupt to not be in IRAM in order to make them more friendly to users and the things they want to do in them, but have provided a way to compile Arduino with IRAM support, which is highly advanced topic and not something that is at all recommended. With that said, many things that need to be in IRAM are in IRAM inside ESP-IDF on which Arduino is built.

[hajosc]

I'm fully aware of the limitstions of putting an interrupt into IRAM. I consider interrupts an advanced topic to start with; run times, race conditions when exchanging data with the process level, debugging methodology, etc. As such I'd expect a user to be able to handle IRAM memory size as well.
Anyways, it's your decision to dumb it down and make user interrupts incompatible with other libraries such as Flash FS. But to save other users lots of time and grievance you could at least, as I mentioned above, clearly mark the limitations of your implementation; I.e. interrupts won't trigger during Flash write/erase. And possibly others, I do observe some other inconsistency which maybe has to do with timing of flash access, cache misses; haven't dug deeper into that.

[SuGlider]

The way for having ISRs placed in IRAM is to build the Arduino User Application using Arduino as IDF Component building process and setting whatever necessary using idf.py menuconfig

https://docs.espressif.com/projects/arduino-esp32/en/latest/esp-idf_component.html

[me-no-dev]

Or create a file in your sketch folder called "build_opt.h", add inside -D CONFIG_ARDUINO_ISR_IRAM=1 and see where that takes you.

There are cases where if you combine enough IDF parts in your sketch, you will exhaust IRAM even with that option off in Arduino.

Good luck!