Before this, CIRCUITPY would start at 1MB anyway. This appeared to work
only because I hadn't checked the actual size of the CIRCUITPY drive,
and because until now the flash hadn't actually crossed that 1MB
boundary into CIRCUITPY storage.
WARNING: on pico_w, upgrading/downgrading CircuitPython across this commit
boundary will erase the CIRCUITPY filesystem. After this commit,
switching between pico and pico_w firmware will erase the CIRCUITPY
filesystem
For RP2040 boards, we now change the default flash size based on
the configured flash. We will still try to read the size from the
flash first.
Fixes#4874
This switches stage2 to C and uses Jinja to change the C code based
on flash settings from https://github.com/adafruit/nvm.toml. It
produces the fastest settings for the given set of external flashes.
Flash size is no longer hard coded so switching flashes with similar
capabilities but different sizes should *just work*.
This PR also places "ITCM" code in RAM to save the XIP cache for
code execution. Further optimization is possible. A blink code.py
still requires a number of flash fetches every blink.
Fixes#4041
The RP2040 is new microcontroller from Raspberry Pi that features
two Cortex M0s and eight PIO state machines that are good for
crunching lots of data. It has 264k RAM and a built in UF2
bootloader too.
Datasheet: https://pico.raspberrypi.org/files/rp2040_datasheet.pdf
