From 1160635608ebeaf3868a327803c0ca248f549123 Mon Sep 17 00:00:00 2001
From: Scott Shawcroft <scott@tannewt.org>
Date: Thu, 16 Jul 2020 19:02:26 -0700
Subject: [PATCH] Enable PYSTACK to keep function state out of the heap

---
 main.c                  | 8 ++++++++
 py/circuitpy_mpconfig.h | 5 +++++
 2 files changed, 13 insertions(+)

diff --git a/main.c b/main.c
index f928d0d62f..f1dfa63c6f 100755
--- a/main.c
+++ b/main.c
@@ -97,6 +97,10 @@ void do_str(const char *src, mp_parse_input_kind_t input_kind) {
     }
 }
 
+#if MICROPY_ENABLE_PYSTACK
+static size_t PLACE_IN_DTCM_BSS(_pystack)[CIRCUITPY_PYSTACK_SIZE / sizeof(size_t)];
+#endif
+
 void start_mp(supervisor_allocation* heap) {
     reset_status_led();
     autoreload_stop();
@@ -125,6 +129,10 @@ void start_mp(supervisor_allocation* heap) {
     // Clear the readline history. It references the heap we're about to destroy.
     readline_init0();
 
+    #if MICROPY_ENABLE_PYSTACK
+    mp_pystack_init(_pystack, _pystack + sizeof(_pystack));
+    #endif
+
     #if MICROPY_ENABLE_GC
     gc_init(heap->ptr, heap->ptr + heap->length / 4);
     #endif
diff --git a/py/circuitpy_mpconfig.h b/py/circuitpy_mpconfig.h
index d05a246fce..a7853fabda 100644
--- a/py/circuitpy_mpconfig.h
+++ b/py/circuitpy_mpconfig.h
@@ -119,6 +119,7 @@
 #define MICROPY_QSTR_BYTES_IN_HASH       (1)
 #define MICROPY_REPL_AUTO_INDENT         (1)
 #define MICROPY_REPL_EVENT_DRIVEN        (0)
+#define MICROPY_ENABLE_PYSTACK           (1)
 #define MICROPY_STACK_CHECK              (1)
 #define MICROPY_STREAMS_NON_BLOCK        (1)
 #ifndef MICROPY_USE_INTERNAL_PRINTF
@@ -785,6 +786,10 @@ void supervisor_run_background_tasks_if_tick(void);
 #define CIRCUITPY_FILESYSTEM_FLUSH_INTERVAL_MS 1000
 #endif
 
+#ifndef CIRCUITPY_PYSTACK_SIZE
+#define CIRCUITPY_PYSTACK_SIZE 1024
+#endif
+
 #define CIRCUITPY_BOOT_OUTPUT_FILE "/boot_out.txt"
 
 #define CIRCUITPY_VERBOSE_BLE 0