mp_spiflash_read had a bug in it where "dest" and "addr" were incremented
twice for a certain special case. This was fixed, which then allowed the
function to be simplified to reduce code size.
mp_spiflash_write had a bug in it where "src" was not incremented correctly
for the case where the data to be written included the caching buffer as
well as some bytes after this buffer. This was fixed and the resulting
code simplified.
This patch alters the SPI-flash memory driver so that it uses the new
low-level C SPI protocol (from drivers/bus/spi.h) instead of the uPy SPI
protocol (from extmod/machine_spi.h). This allows the SPI-flash driver to
be used independently from the uPy runtime.
The spiflash memory driver is reworked to allow the underlying bus to be
either normal SPI or QSPI. In both cases the bus can be implemented in
software or hardware, as long as the spiflash driver is passed the correct
configuration structure.
The SPI flash driver now supports using an arbitrary SPI object to
communicate with the flash chip, and in particular can use a hardware SPI
peripheral.
