nrf/machine/timer: Support soft IRQ timer callbacks.

arachsys · arachsys · commit f700460d62db · 2025-06-29T11:03:43.000+01:00
machine.Timer() has inconsistent behaviour between ports: some run
callbacks in hard IRQ context whereas others schedule them like soft IRQs.

The rp2 Timer constructor now has a hard= argument to explicitly choose
between these. Add support for this to the nrf port, setting the default
to True to match the existing behaviour.

The existing hard-IRQ path doesn't seem to call mp_sched_lock() or
gc_lock() before using mp_call_function_1(callback, self) from IRQ context.
This is probably incorrect unless I have missed something; if so, I will
fix it too.

Signed-off-by: Chris Webb &lt;chris@arachsys.com&gt;
diff --git a/ports/nrf/modules/machine/timer.c b/ports/nrf/modules/machine/timer.c
@@ -39,6 +39,7 @@ enum {
 typedef struct _machine_timer_obj_t {
     mp_obj_base_t base;
     nrfx_timer_t p_instance;
+    bool ishard;
 } machine_timer_obj_t;
 
 static mp_obj_t machine_timer_callbacks[] = {
@@ -89,20 +90,25 @@ static void timer_event_handler(nrf_timer_event_t event_type, void *p_context) {
     machine_timer_obj_t *self = p_context;
     mp_obj_t callback = machine_timer_callbacks[self->p_instance.instance_id];
     if (callback != NULL) {
-        mp_call_function_1(callback, self);
+        if (self->ishard) {
+            mp_call_function_1(callback, self);
+        } else {
+            mp_sched_schedule(callback, self);
+        }
     }
 }
 
 /******************************************************************************/
 /* MicroPython bindings for machine API                                       */
 
 static mp_obj_t machine_timer_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *all_args) {
-    enum { ARG_id, ARG_period, ARG_mode, ARG_callback };
+    enum { ARG_id, ARG_period, ARG_mode, ARG_callback, ARG_hard };
     static const mp_arg_t allowed_args[] = {
         { MP_QSTR_id,       MP_ARG_OBJ, {.u_obj = MP_OBJ_NEW_SMALL_INT(-1)} },
         { MP_QSTR_period,   MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 1000000} }, // 1 second
         { MP_QSTR_mode,     MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = TIMER_MODE_PERIODIC} },
         { MP_QSTR_callback, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_obj = mp_const_none} },
+        { MP_QSTR_hard,     MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = true} },
     };
 
     // parse args
@@ -133,6 +139,7 @@ static mp_obj_t machine_timer_make_new(const mp_obj_type_t *type, size_t n_args,
     } else {
         mp_raise_ValueError(MP_ERROR_TEXT("callback must be a function"));
     }
+    self->ishard = args[ARG_hard].u_bool;
 
     // Timer peripheral usage:
     // Every timer instance has a number of capture/compare (CC) registers.
