shared/tinyusb: Update some code comments for runtime USB.

Updates a few code comments that were out of date or poorly worded. No code
changes.

This work was funded through GitHub Sponsors.
Signed-off-by: Angus Gratton <angus@redyak.com.au>

shared/tinyusb/mp_usbd_runtime.c

@@ -44,7 +44,7 @@
 #include "device/usbd_pvt.h"
 #endif
 
-static bool in_usbd_task; // Flags if mp_usbd_task() is processing already
+static bool in_usbd_task; // Flags if mp_usbd_task() is currently running
 
 // Some top-level functions that manage global TinyUSB USBD state, not the
 // singleton object visible to Python
@@ -250,8 +250,8 @@ static uint16_t _runtime_dev_claim_itfs(tusb_desc_interface_t const *itf_desc, u
 // configuration. Returns number of bytes to claim from descriptors pointed to
 // by itf_desc.
 //
-// This is a little fiddly as it's called before any compiled-in "static"
-// TinyUSB drivers, but we don't want to override those.
+// This is a little fiddly as it's called before any built-in TinyUSB drivers,
+// but we don't want to override those.
 //
 // Also, TinyUSB expects us to know how many interfaces to claim for each time
 // this function is called, and will behave unexpectedly if we claim the wrong
@@ -266,7 +266,7 @@ static uint16_t runtime_dev_open(uint8_t rhport, tusb_desc_interface_t const *it
         return 0;
     }
 
-    // If TinyUSB built-in drivers are enabled, don't claim any interface in the static range
+    // If TinyUSB built-in drivers are enabled, don't claim any interface in the built-in range
     if (mp_usb_device_builtin_enabled(usbd) && itf_desc->bInterfaceNumber < USBD_ITF_BUILTIN_MAX) {
         return 0;
     }
@@ -400,7 +400,7 @@ usbd_class_driver_t const *usbd_app_driver_get_cb(uint8_t *driver_count) {
 
 // Top-level USB device subsystem init.
 //
-// Makes an on-demand call to mp_usbd_activate(), if USB is needed.
+// Initialises TinyUSB and/or re-activates it, provided USB is needed.
 //
 // This is called on any soft reset after boot.py runs, or on demand if the
 // user activates USB and it hasn't activated yet.
@@ -414,7 +414,7 @@ void mp_usbd_init(void) {
         // Builtin  drivers are available, so initialise as defaults
         need_usb = true;
         #else
-        // No static drivers, nothing to initialise
+        // No builtin drivers, nothing to initialise
         need_usb = false;
         #endif
     } else {
@@ -472,7 +472,10 @@ static void mp_usbd_disconnect(mp_obj_usb_device_t *usbd) {
     bool was_connected = tud_connected();
     tud_disconnect();
     if (was_connected) {
-        mp_hal_delay_ms(50); // TODO: Always???
+        // Need to ensure a long enough delay before TinyUSB re-connects that
+        // the host triggers a bus reset. This may happen anyway, but delaying here
+        // lets us be "belt and braces" sure.
+        mp_hal_delay_ms(50);
     }
 }