This targets the 64-bit CPU Raspberry Pis. The BCM2711 on the Pi 4
and the BCM2837 on the Pi 3 and Zero 2W. There are 64-bit fixes
outside of the ports directory for it.
There are a couple other cleanups that were incidental:
* Use const mcu_pin_obj_t instead of omitting the const. The structs
themselves are const because they are in ROM.
* Use PTR <-> OBJ conversions in more places. They were found when
mp_obj_t was set to an integer type rather than pointer.
* Optimize submodule checkout because the Pi submodules are heavy
and unnecessary for the vast majority of builds.
Fixes#4314
This increases write rates (of gifio from #5490) from about 2.4fps to over
5fps by making more efficient use of the SD card protocol.
Because of details of oofatfs, it usually manages 64 writes in a single
CMD25, then two writes in a different area of the SD card (presumably,
filesystem metadata). I couldn't find where to increase "64" to a higher
number. This may depend on the allocation size of the filesystem.
I tried preallocating too, but oddly it significantly lowered the write
rate.
Any trailing data is committed when the file is close()d, or when
the `sync` method of the SDCard object is called.
Testing performed: That a card is successfully mounted on Pygamer with
the built in SD card slot
This module is enabled for most FULL_BUILD boards, but is disabled for
samd21 ("M0"), litex, and pca10100 for various reasons.
Timon
Jeff Epler