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rp2: Remove 1ms timeout to make idle waiting tickless. 

The main motivation for doing this was to reduce the latency when the
system is woken by a USB interrupt.  The best_effort_wfe_or_timeout()
function calls into the pico-sdk dynamic timer framework which sets up a
new dynamic timer instance each time, and then has to tear it down before
continuing after a WFE.

Testing Python interrupt latency, it seems to be improved by about 12us
(from average of 46us to 34us running a Pin IRQ).  C-based "scheduled
nodes" should see even lower latency.

This work was funded through GitHub Sponsors.

Signed-off-by: Angus Gratton <angus@redyak.com.au>
This commit is contained in:
Angus Gratton 2023-10-31 16:42:10 +11:00 committed by Damien George
parent b41055a5a3
commit 8c432ea2d4
2 changed files with 2 additions and 2 deletions
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2
ports/rp2/modmachine.c
View File

@ -111,7 +111,7 @@ STATIC mp_obj_t machine_freq(size_t n_args, const mp_obj_t *args) {
STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_freq_obj, 0, 1, machine_freq);
STATIC mp_obj_t machine_idle(void) {
best_effort_wfe_or_timeout(make_timeout_time_ms(1));
__wfe();
return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_0(machine_idle_obj, machine_idle);

2
ports/rp2/mpconfigport.h
View File

@ -274,7 +274,7 @@ extern void mp_thread_end_atomic_section(uint32_t);
#define MICROPY_EVENT_POLL_HOOK \
do { \
MICROPY_EVENT_POLL_HOOK_FAST; \
best_effort_wfe_or_timeout(make_timeout_time_ms(1)); \
__wfe(); \
} while (0);
#define MICROPY_MAKE_POINTER_CALLABLE(p) ((void *)((mp_uint_t)(p) | 1))