Adds a lot of code, makes IRQs a bit less efficient, but is very useful
for debugging. Usage: pyb.irq_stats() returns a memory view that can be
read and written, eg:
list(pyb.irq_stats())
pyb.irq_stats()[0]
pyb.irq_stats()[0] = 0
The patch provides general IRQ_ENTER() and IRQ_EXIT() macros that can be
modified to provide further IRQ statistics if desired.
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.
These functions are generally 1 machine instruction, and are used in
critical code, so makes sense to have them inline.
Also leave these functions uninverted (ie 0 means enable, 1 means
disable) and provide macro constants if you really need to distinguish
the states. This makes for smaller code as well (combined with
inlining).
Applied to teensy port as well.
Damien George