They are the same as the existing raw constants (namely 0, 1, 2) but we
want to explicitly show that one can use the HAL's constants if necessary
(eg the mpconfigboard.h files do use the HAL's constants to define the
pull state of certain configurable pins).
So long as a port defines relevant mp_hal_pin_xxx functions (and delay) it
can make use of this software SPI class without the need for additional
code.
Add 2 macros in mphalport.h that clean and invalidate data caches only on
STM32F7 MCUs. They are needed to ensure the cache coherency before/after
DMA transferts.
* MP_HAL_CLEANINVALIDATE_DCACHE cleans and invalidate the data cache. It
must be called before starting a DMA transfer from the peripheral to the
RAM memory.
* MP_HAL_CLEAN_DCACHE cleans the data cache. It must be called before
starting a DMA transfert from the RAM memory to the peripheral.
These macros are called in sdcard.c, before reading from and writing to
the SDCard, when DMA is used.
__GPIOI_CLK_ENABLE is defined in hal/l4/inc/Legacy/stm32_hal_legacy.h
as __HAL_RCC_GPIOI_CLK_ENABLE, and that latter macro is not defined
anywhere else (because the L4 does not have port GPIOI). So the test
for GPIOI is needed, along with the test for the CLK_ENABLE macro.
py/mphal.h contains declarations for generic mp_hal_XXX functions, such
as stdio and delay/ticks, which ports should provide definitions for. A
port will also provide mphalport.h with further HAL declarations.
