Improve resolution of mp_hal_delay_ms() to subticks.

ports/broadcom/supervisor/port.c

@@ -143,7 +143,11 @@ uint64_t port_get_raw_ticks(uint8_t *subticks) {
     }
     COMPLETE_MEMORY_READS;
     uint64_t microseconds = hi << 32 | lo;
-    return 1024 * (microseconds / 1000000) + (microseconds % 1000000) / 977;
+    int64_t all_subticks = microseconds * 512 / 15625;
+    if (subticks != NULL) {
+        *subticks = all_subticks % 32;
+    }
+    return all_subticks / 32;
 }
 
 void TIMER_1_IRQHandler(void) {

ports/cxd56/supervisor/port.c

@@ -124,7 +124,9 @@ void board_timerhook(void) {
 
 uint64_t port_get_raw_ticks(uint8_t *subticks) {
     uint64_t count = cxd56_rtc_count();
-    *subticks = count % 32;
+    if (subticks != NULL) {
+        *subticks = count % 32;
+    }
 
     return count / 32;
 }

ports/litex/supervisor/port.c

@@ -114,6 +114,9 @@ uint64_t port_get_raw_ticks(uint8_t *subticks) {
     common_hal_mcu_disable_interrupts();
     uint64_t raw_tick_snapshot = raw_ticks;
     common_hal_mcu_enable_interrupts();
+    if (subticks != NULL) {
+        *subticks = 0;
+    }
     return raw_tick_snapshot;
 }
 

ports/raspberrypi/supervisor/port.c

@@ -491,11 +491,11 @@ static volatile bool ticks_enabled;
 static volatile bool _woken_up;
 
 uint64_t port_get_raw_ticks(uint8_t *subticks) {
-    uint64_t microseconds = time_us_64();
+    int64_t all_subticks = time_us_64() * 512 / 15625;
     if (subticks != NULL) {
-        *subticks = (uint8_t)(((microseconds % 1000000) % 977) / 31);
+        *subticks = all_subticks % 32;
     }
-    return 1024 * (microseconds / 1000000) + (microseconds % 1000000) / 977;
+    return all_subticks / 32;
 }
 
 static void _tick_callback(uint alarm_num) {

supervisor/shared/tick.c

@@ -85,6 +85,13 @@ void supervisor_tick(void) {
     background_callback_add(&tick_callback, supervisor_background_tick, NULL);
 }
 
+uint64_t supervisor_get_raw_subticks(void) {
+    uint64_t ticks;
+    uint8_t subticks;
+    ticks = port_get_raw_ticks(&subticks);
+    return (ticks << 5) | subticks;
+}
+
 uint64_t supervisor_ticks_ms64() {
     uint64_t result;
     result = port_get_raw_ticks(NULL);
@@ -97,26 +104,30 @@ uint32_t supervisor_ticks_ms32() {
 }
 
 void mp_hal_delay_ms(mp_uint_t delay_ms) {
-    uint64_t start_tick = port_get_raw_ticks(NULL);
-    // Adjust the delay to ticks vs ms.
-    uint64_t delay_ticks = (delay_ms * (uint64_t)1024) / 1000;
-    uint64_t end_tick = start_tick + delay_ticks;
-    int64_t remaining = delay_ticks;
+    uint64_t start_subtick = supervisor_get_raw_subticks();
+    // Convert delay from ms to subticks
+    uint64_t delay_subticks = (delay_ms * (uint64_t)32768) / 1000;
+    uint64_t end_subtick = start_subtick + delay_subticks;
+    int64_t remaining = delay_subticks;
 
     // Loop until we've waited long enough or we've been CTRL-Ced by autoreload
     // or the user.
     while (remaining > 0 && !mp_hal_is_interrupted()) {
         RUN_BACKGROUND_TASKS;
-        remaining = end_tick - port_get_raw_ticks(NULL);
-        // We break a bit early so we don't risk setting the alarm before the time when we call
-        // sleep.
-        if (remaining < 1) {
+        // Exit if interrupted while running background tasks
+        if (mp_hal_is_interrupted()) {
             break;
         }
-        port_interrupt_after_ticks(remaining);
-        // Idle until an interrupt happens.
-        port_idle_until_interrupt();
-        remaining = end_tick - port_get_raw_ticks(NULL);
+        // Recalculate remaining delay after running background tasks
+        remaining = end_subtick - supervisor_get_raw_subticks();
+        // If remaining delay is less than 1 tick, idle loop until end of delay
+        int64_t remaining_ticks = remaining / 32;
+        if (remaining_ticks > 0) {
+            port_interrupt_after_ticks(remaining_ticks);
+            // Idle until an interrupt happens.
+            port_idle_until_interrupt();
+        }
+        remaining = end_subtick - supervisor_get_raw_subticks();
     }
 }
 

supervisor/shared/tick.h

@@ -33,6 +33,13 @@ extern uint32_t supervisor_ticks_ms32(void);
  */
 extern uint64_t supervisor_ticks_ms64(void);
 
+/** @brief Get 64-bit current time in subticks
+ *
+ * Time is returned as a 64-bit count of subticks where each subtick is 1/32768
+ * of a second.
+ */
+extern uint64_t supervisor_get_raw_subticks(void);
+
 extern void supervisor_enable_tick(void);
 extern void supervisor_disable_tick(void);