shared/tinyusb: Add optional port-specific hook on USBD init.

This allows a port to do hardware initialization just before the TinyUSB
stack is brought up.  That means the hardware is only turned on when it's
needed.

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

Author: dpgeorge

shared/tinyusb/mp_usbd.h

@@ -45,6 +45,10 @@
 #define MICROPY_WRAP_TUD_EVENT_HOOK_CB(name) name
 #endif
 
+#ifndef MICROPY_HW_TINYUSB_LL_INIT
+#define MICROPY_HW_TINYUSB_LL_INIT()
+#endif
+
 #if MICROPY_HW_ENABLE_USBDEV
 
 #include "py/obj.h"
@@ -102,6 +106,7 @@ void mp_usbd_task_callback(mp_sched_node_t *node);
 static inline void mp_usbd_init(void) {
     // Without runtime USB support, this can be a thin wrapper wrapper around tusb_init()
     // which is called in the below helper function.
+    MICROPY_HW_TINYUSB_LL_INIT();
     mp_usbd_init_tud();
 }
 

shared/tinyusb/mp_usbd_runtime.c

@@ -430,6 +430,8 @@ void mp_usbd_init(void) {
     }
 
     if (need_usb) {
+        // Call any port-specific initialization code.
+        MICROPY_HW_TINYUSB_LL_INIT();
         // The following will call tusb_init(), which is safe to call redundantly.
         mp_usbd_init_tud();
         // Reconnect if mp_usbd_deinit() has disconnected.