rp2/mpconfigport: Allow MICROPY_PY_THREAD to be disabled by a board.

Signed-off-by: Damien George <damien@micropython.org>

ports/rp2/mpconfigport.h

@@ -89,9 +89,11 @@
 // Fine control over Python builtins, classes, modules, etc
 #define MICROPY_PY_BUILTINS_HELP_TEXT           rp2_help_text
 #define MICROPY_PY_SYS_PLATFORM                 "rp2"
+#ifndef MICROPY_PY_THREAD
 #define MICROPY_PY_THREAD                       (1)
 #define MICROPY_PY_THREAD_GIL                   (0)
 #define MICROPY_THREAD_YIELD()                  mp_handle_pending(true)
+#endif
 
 // Extended modules
 #define MICROPY_EPOCH_IS_1970                   (1)

ports/rp2/mphalport.h

@@ -37,8 +37,13 @@
 #define MICROPY_HW_USB_CDC_TX_TIMEOUT (500)
 
 // Entering a critical section.
+#if MICROPY_PY_THREAD
 #define MICROPY_BEGIN_ATOMIC_SECTION()     mp_thread_begin_atomic_section()
 #define MICROPY_END_ATOMIC_SECTION(state)  mp_thread_end_atomic_section(state)
+#else
+#define MICROPY_BEGIN_ATOMIC_SECTION()     save_and_disable_interrupts()
+#define MICROPY_END_ATOMIC_SECTION(state)  restore_interrupts(state)
+#endif
 
 #define MICROPY_PY_PENDSV_ENTER   pendsv_suspend()
 #define MICROPY_PY_PENDSV_EXIT    pendsv_resume()