rp2: Fix wakeup from WFE on core1.

If core1 executes `mp_wfe_or_timeout()` then it needs to receive an
interrupt or a SEV to resume execution, but the soft timer interrupt only
fires on core 0.  This fix adds a SEV to the soft timer interrupt handler.

This issue was masked by the issue fixed in the previous commit, as WFE
previously wasn't suspending properly.

Verified via the existing thread_sleep2 test.

This work was funded through GitHub Sponsors.

Signed-off-by: Angus Gratton <[email protected]>

Author: projectgus

ports/rp2/mphalport.c

@@ -228,6 +228,13 @@ static void soft_timer_hardware_callback(unsigned int alarm_num) {
     // The timer alarm ISR needs to call here and trigger PendSV dispatch via
     // a second ISR, as PendSV may be currently suspended by the other CPU.
     pendsv_schedule_dispatch(PENDSV_DISPATCH_SOFT_TIMER, soft_timer_handler);
+
+    // This ISR only runs on core0, but if core1 is running Python code then it
+    // may be blocked in WFE so wake it up as well. Unfortunately this also sets
+    // the event flag on core0, so a subsequent WFE on this core will not suspend
+    if (core1_entry != NULL) {
+        __sev();
+    }
 }
 
 void soft_timer_init(void) {

ports/rp2/mpthreadport.c

@@ -39,7 +39,7 @@ extern uint8_t __StackTop, __StackBottom;
 void *core_state[2];
 
 // This will be non-NULL while Python code is executing.
-static void *(*core1_entry)(void *) = NULL;
+core_entry_func_t core1_entry = NULL;
 
 static void *core1_arg = NULL;
 static uint32_t *core1_stack = NULL;

ports/rp2/mpthreadport.h

@@ -32,6 +32,10 @@ typedef struct mutex mp_thread_mutex_t;
 
 extern void *core_state[2];
 
+typedef void *(*core_entry_func_t)(void *);
+
+extern core_entry_func_t core1_entry;
+
 void mp_thread_init(void);
 void mp_thread_deinit(void);
 void mp_thread_gc_others(void);