From 3ccf644dd0afd85ad8d8c6c67494cebab172b5a8 Mon Sep 17 00:00:00 2001
From: Scott Shawcroft <scott@tannewt.org>
Date: Fri, 9 Oct 2020 12:53:00 -0700
Subject: [PATCH] Fix autoreload on SAMD21

The issue was that a time.sleep() would set the RTC wake up
further into the future even if we wanted to tick every ms. Ticking
every ms is used to time the autoreload delay and without it,
autoreload doesn't work.

Fixes #3528
---
 ports/atmel-samd/supervisor/port.c | 58 +++++++++++++++++-------------
 1 file changed, 34 insertions(+), 24 deletions(-)

diff --git a/ports/atmel-samd/supervisor/port.c b/ports/atmel-samd/supervisor/port.c
index 8d52c30c53..e69062296d 100644
--- a/ports/atmel-samd/supervisor/port.c
+++ b/ports/atmel-samd/supervisor/port.c
@@ -430,6 +430,33 @@ uint32_t port_get_saved_word(void) {
 static volatile uint64_t overflowed_ticks = 0;
 static volatile bool _ticks_enabled = false;
 
+static uint32_t _get_count(void) {
+    #ifdef SAM_D5X_E5X
+    while ((RTC->MODE0.SYNCBUSY.reg & (RTC_MODE0_SYNCBUSY_COUNTSYNC | RTC_MODE0_SYNCBUSY_COUNT)) != 0) {}
+    #endif
+    #ifdef SAMD21
+    while (RTC->MODE0.STATUS.bit.SYNCBUSY != 0) {}
+    #endif
+
+    return RTC->MODE0.COUNT.reg;
+}
+
+static void _port_interrupt_after_ticks(uint32_t ticks) {
+    uint32_t current_ticks = _get_count();
+    if (ticks > 1 << 28) {
+        // We'll interrupt sooner with an overflow.
+        return;
+    }
+#ifdef SAMD21
+    if (hold_interrupt) {
+        return;
+    }
+#endif
+    RTC->MODE0.COMP[0].reg = current_ticks + (ticks << 4);
+    RTC->MODE0.INTFLAG.reg = RTC_MODE0_INTFLAG_CMP0;
+    RTC->MODE0.INTENSET.reg = RTC_MODE0_INTENSET_CMP0;
+}
+
 void RTC_Handler(void) {
     uint32_t intflag = RTC->MODE0.INTFLAG.reg;
     if (intflag & RTC_MODE0_INTFLAG_OVF) {
@@ -452,7 +479,7 @@ void RTC_Handler(void) {
             supervisor_tick();
             // Check _ticks_enabled again because a tick handler may have turned it off.
             if (_ticks_enabled) {
-                port_interrupt_after_ticks(1);
+                _port_interrupt_after_ticks(1);
             }
         }
         #endif
@@ -462,17 +489,6 @@ void RTC_Handler(void) {
     }
 }
 
-static uint32_t _get_count(void) {
-    #ifdef SAM_D5X_E5X
-    while ((RTC->MODE0.SYNCBUSY.reg & (RTC_MODE0_SYNCBUSY_COUNTSYNC | RTC_MODE0_SYNCBUSY_COUNT)) != 0) {}
-    #endif
-    #ifdef SAMD21
-    while (RTC->MODE0.STATUS.bit.SYNCBUSY != 0) {}
-    #endif
-
-    return RTC->MODE0.COUNT.reg;
-}
-
 uint64_t port_get_raw_ticks(uint8_t* subticks) {
     uint32_t current_ticks = _get_count();
     if (subticks != NULL) {
@@ -490,7 +506,7 @@ void port_enable_tick(void) {
     #endif
     #ifdef SAMD21
     _ticks_enabled = true;
-    port_interrupt_after_ticks(1);
+    _port_interrupt_after_ticks(1);
     #endif
 }
 
@@ -505,20 +521,14 @@ void port_disable_tick(void) {
     #endif
 }
 
+// This is called by sleep, we ignore it when our ticks are enabled because
+// they'll wake us up earlier. If we don't, we'll mess up ticks by overwriting
+// the next RTC wake up time.
 void port_interrupt_after_ticks(uint32_t ticks) {
-    uint32_t current_ticks = _get_count();
-    if (ticks > 1 << 28) {
-        // We'll interrupt sooner with an overflow.
+    if (_ticks_enabled) {
         return;
     }
-#ifdef SAMD21
-    if (hold_interrupt) {
-        return;
-    }
-#endif
-    RTC->MODE0.COMP[0].reg = current_ticks + (ticks << 4);
-    RTC->MODE0.INTFLAG.reg = RTC_MODE0_INTFLAG_CMP0;
-    RTC->MODE0.INTENSET.reg = RTC_MODE0_INTENSET_CMP0;
+    _port_interrupt_after_ticks(ticks);
 }
 
 void port_sleep_until_interrupt(void) {