Reducing boot-time

[davefes]

At a rough guess it is taking my camera (2024 version) about 2 seconds
to come out of deepsleep until the image is captured.

@glenn20
https://github.com/glenn20/upy-esp32-experiments/tree/main/OptimisingMicropythonBootTime
has done investigations into ways of reducing boot time.

A: Reduce time to boot to app_main():
has been done in mainline, but don't know if it is included in your 2024 firmware.

B: Execute app (deepsleep reboot) from frozen _boot.py module:
seems a worthwhile modification which the user can build in themselves.

C: Skip nvs_flash_init() on boot if waking from deepsleep:
I want WiFi, but maybe it could be done after the image has been
captured.

D: Skip initialisation of SPIRAM on boot if waking from deepsleep:
Maybe relevant.

Interested in your comments about reducing boot-time. If B: gives the
biggest improvement maybe I need to have another attempt at freezing
my app_main.

Thank you.