zephyr: Add threading support.

This commit implements the `_thread` module on the zephyr port.

Due to the fact that we are still using a rather old version of Zephyr,
`CONFIG_DYNAMIC_THREAD` is not available and therefore the stack for
threads cannot be allocated dynamically, only at compile time.  So for the
time being and for the purpose of this commit, a maximum of 4 Zephyr
threads (besides the main thread) can be created.  Once we manage to update
to the latest version of Zephyr this won't be a problem anymore.

Configuration for the nrf52840dk is added as part of this change, because
this board was used to test the threading support.

The Zephyr option `CONFIG_THREAD_CUSTOM_DATA` is used to enable threading
on a per board basis.  The `thread.conf` file is added as a convenient way
to enable threading.

Signed-off-by: danicampora <[email protected]>

ports/zephyr/CMakeLists.txt

@@ -47,6 +47,7 @@ set(MICROPY_SOURCE_PORT
     mphalport.c
     uart_core.c
     zephyr_storage.c
+    mpthreadport.c
 )
 list(TRANSFORM MICROPY_SOURCE_PORT PREPEND ${MICROPY_PORT_DIR}/)
 

ports/zephyr/README.md

@@ -63,6 +63,11 @@ To build for QEMU instead:
 
     $ west build -b qemu_x86 ~/micropython/ports/zephyr
 
+To build any board with the `_thread` module enabled,
+add `-DOVERLAY_CONFIG=thread.conf`, for instance:
+
+    $ west build -b frdm_k64f ~/micropython/ports/zephyr -DOVERLAY_CONFIG=thread.conf
+
 Consult the Zephyr documentation above for the list of
 supported boards.  Board configuration files appearing in `ports/zephyr/boards/`
 correspond to boards that have been tested with MicroPython and may have

ports/zephyr/boards/nrf52840dk_nrf52840.conf

@@ -0,0 +1,13 @@
+CONFIG_NETWORKING=n
+CONFIG_BT=y
+CONFIG_BT_DEVICE_NAME_DYNAMIC=y
+CONFIG_BT_PERIPHERAL=y
+CONFIG_BT_CENTRAL=y
+
+CONFIG_MICROPY_HEAP_SIZE=98304
+CONFIG_MAIN_STACK_SIZE=8192
+
+# CONFIG_DYNAMIC_THREAD=y
+CONFIG_THREAD_CUSTOM_DATA=y
+CONFIG_THREAD_MONITOR=y
+CONFIG_THREAD_STACK_INFO=y

ports/zephyr/main.c

@@ -114,14 +114,20 @@ static void vfs_init(void) {
 #endif // MICROPY_VFS
 
 int real_main(void) {
-    mp_stack_ctrl_init();
-    // Make MicroPython's stack limit somewhat smaller than full stack available
-    mp_stack_set_limit(CONFIG_MAIN_STACK_SIZE - 512);
+    volatile int stack_dummy = 0;
+
+    #if MICROPY_PY_THREAD
+    struct k_thread *z_thread = (struct k_thread *)k_current_get();
+    mp_thread_init((void *)z_thread->stack_info.start, z_thread->stack_info.size / sizeof(uintptr_t));
+    #endif
 
     init_zephyr();
     mp_hal_init();
 
 soft_reset:
+    mp_stack_set_top((void *)&stack_dummy);
+    // Make MicroPython's stack limit somewhat smaller than full stack available
+    mp_stack_set_limit(CONFIG_MAIN_STACK_SIZE - 512);
     #if MICROPY_ENABLE_GC
     gc_init(heap, heap + sizeof(heap));
     #endif
@@ -160,6 +166,14 @@ int real_main(void) {
     machine_pin_deinit();
     #endif
 
+    #if MICROPY_PY_THREAD
+    mp_thread_deinit();
+    gc_collect();
+    #endif
+
+    gc_sweep_all();
+    mp_deinit();
+
     goto soft_reset;
 
     return 0;
@@ -171,6 +185,9 @@ void gc_collect(void) {
     void *dummy;
     gc_collect_start();
     gc_collect_root(&dummy, ((mp_uint_t)MP_STATE_THREAD(stack_top) - (mp_uint_t)&dummy) / sizeof(mp_uint_t));
+    #if MICROPY_PY_THREAD
+    mp_thread_gc_others();
+    #endif
     gc_collect_end();
 }
 

ports/zephyr/mpconfigport.h

@@ -113,6 +113,13 @@
 #define MICROPY_COMP_CONST (0)
 #define MICROPY_COMP_DOUBLE_TUPLE_ASSIGN (0)
 
+// When CONFIG_THREAD_CUSTOM_DATA is enabled, MICROPY_PY_THREAD is enabled automatically
+#ifdef CONFIG_THREAD_CUSTOM_DATA
+#define MICROPY_PY_THREAD                   (1)
+#define MICROPY_PY_THREAD_GIL               (1)
+#define MICROPY_PY_THREAD_GIL_VM_DIVISOR    (32)
+#endif
+
 void mp_hal_signal_event(void);
 #define MICROPY_SCHED_HOOK_SCHEDULED mp_hal_signal_event()
 
@@ -139,3 +146,21 @@ typedef long mp_off_t;
 // extra built in names to add to the global namespace
 #define MICROPY_PORT_BUILTINS \
     { MP_ROM_QSTR(MP_QSTR_open), MP_ROM_PTR(&mp_builtin_open_obj) },
+
+#if MICROPY_PY_THREAD
+#define MICROPY_EVENT_POLL_HOOK \
+    do { \
+        extern void mp_handle_pending(bool); \
+        mp_handle_pending(true); \
+        MP_THREAD_GIL_EXIT(); \
+        k_msleep(1); \
+        MP_THREAD_GIL_ENTER(); \
+    } while (0);
+#else
+#define MICROPY_EVENT_POLL_HOOK \
+    do { \
+        extern void mp_handle_pending(bool); \
+        mp_handle_pending(true); \
+        k_msleep(1); \
+    } while (0);
+#endif

ports/zephyr/mpconfigport_minimal.h

@@ -83,3 +83,5 @@ typedef unsigned mp_uint_t; // must be pointer size
 typedef long mp_off_t;
 
 #define MP_STATE_PORT MP_STATE_VM
+
+#define MICROPY_EVENT_POLL_HOOK