Merge pull request #3490 from Precidata/non-blocking-host-v2

Fully asynchrounous host code (v2)

3 files changed, 267 insertions, 171 deletions

diff --git a/src/host/hcd.h b/src/host/hcd.h
index 36a7f5da5..47d672f9e 100644
--- a/src/host/hcd.h
+++ b/src/host/hcd.h
@@ -59,7 +59,7 @@ typedef enum {
   HCD_EVENT_XFER_COMPLETE,
 
   USBH_EVENT_FUNC_CALL, // Not an HCD event
-  HCD_EVENT_COUNT
+  HCD_EVENT_INVALID
 } hcd_eventid_t;
 
 typedef struct {
@@ -72,7 +72,6 @@ typedef struct {
     struct {
       uint8_t hub_addr;
       uint8_t hub_port;
-      uint8_t speed;
     } connection;
 
     // XFER_COMPLETE
diff --git a/src/host/usbh.c b/src/host/usbh.c
index d702e9186..20791340e 100644
--- a/src/host/usbh.c
+++ b/src/host/usbh.c
@@ -169,6 +169,12 @@ static OSAL_SPINLOCK_DEF(_usbh_spin, usbh_int_set);
 OSAL_QUEUE_DEF(usbh_int_set, _usbh_qdef, CFG_TUH_TASK_QUEUE_SZ, hcd_event_t);
 static osal_queue_t _usbh_q;
 
+  #if CFG_TUH_HUB
+// Deferred attachment queue, only needed when using hub
+OSAL_QUEUE_DEF(usbh_int_set, _usbh_daqdef, CFG_TUH_HUB, hcd_event_t);
+static osal_queue_t _usbh_daq;
+  #endif
+
 // Control transfers: since most controllers do not support multiple control transfers
 // on multiple devices concurrently and control transfers are not used much except for
 // enumeration, we will only execute control transfers one at a time.
@@ -184,11 +190,18 @@ typedef struct {
 } usbh_ctrl_xfer_info_t;
 
 typedef struct {
+  tusb_defer_func_t func;
+  uintptr_t         arg;
+  uint32_t          at_ms;
+} usbh_call_after_t;
+
+typedef struct {
   uint8_t controller_id;      // controller ID
   uint8_t enumerating_daddr;  // device address of the device being enumerated
   uint8_t attach_debouncing_bm;  // bitmask for roothub port attach debouncing
   tuh_bus_info_t dev0_bus;    // bus info for dev0 in enumeration
   usbh_ctrl_xfer_info_t ctrl_xfer_info; // control transfer
+  usbh_call_after_t call_after;
 } usbh_data_t;
 
 static usbh_data_t _usbh_data = {
@@ -311,7 +324,8 @@ TU_ATTR_ALWAYS_INLINE static inline usbh_class_driver_t const *get_driver(uint8_
 //--------------------------------------------------------------------+
 // Function Inline and Prototypes
 //--------------------------------------------------------------------+
-static bool enum_new_device(hcd_event_t* event);
+static void enum_new_device(hcd_event_t* event);
+static void enum_delay_async(uintptr_t state);
 static void process_remove_event(hcd_event_t *event);
 static void remove_device_tree(uint8_t rhport, uint8_t hub_addr, uint8_t hub_port);
 static bool usbh_edpt_control_open(uint8_t dev_addr, uint8_t max_packet_size);
@@ -349,6 +363,15 @@ TU_ATTR_ALWAYS_INLINE static inline bool usbh_setup_send(uint8_t daddr, const ui
   return ret;
 }
 
+bool usbh_defer_func_ms_async(uint32_t ms, tusb_defer_func_t func, uintptr_t param) {
+  TU_ASSERT(_usbh_data.call_after.func == NULL);
+  TU_LOG_USBH("USBH schedule function after %u ms\r\n", (unsigned int)ms);
+  _usbh_data.call_after.func  = func;
+  _usbh_data.call_after.arg   = param;
+  _usbh_data.call_after.at_ms = tusb_time_millis_api() + ms;
+  return true;
+}
+
 TU_ATTR_ALWAYS_INLINE static inline void usbh_device_close(uint8_t rhport, uint8_t daddr) {
   hcd_device_close(rhport, daddr);
 
@@ -360,6 +383,10 @@ TU_ATTR_ALWAYS_INLINE static inline void usbh_device_close(uint8_t rhport, uint8
   // invalidate if enumerating
   if (daddr == _usbh_data.enumerating_daddr) {
     _usbh_data.enumerating_daddr = TUSB_INDEX_INVALID_8;
+    // clear enum delay function of the device being removed
+    if (_usbh_data.call_after.func == enum_delay_async) {
+      _usbh_data.call_after.func = NULL;
+    }
   }
 }
 
@@ -493,11 +520,17 @@ bool tuh_rhport_init(uint8_t rhport, const tusb_rhport_init_t* rh_init) {
     _usbh_q = osal_queue_create(&_usbh_qdef);
     TU_ASSERT(_usbh_q != NULL);
 
-#if OSAL_MUTEX_REQUIRED
+  #if CFG_TUH_HUB
+    // Deferred attachment queue
+    _usbh_daq = osal_queue_create(&_usbh_daqdef);
+    TU_ASSERT(_usbh_daq != NULL);
+  #endif
+
+  #if OSAL_MUTEX_REQUIRED
     // Init mutex
     _usbh_mutex = osal_mutex_create(&_usbh_mutexdef);
     TU_ASSERT(_usbh_mutex);
-#endif
+  #endif
 
     // Get application driver if available
     _app_driver = usbh_app_driver_get_cb(&_app_driver_count);
@@ -558,11 +591,16 @@ bool tuh_deinit(uint8_t rhport) {
     osal_queue_delete(_usbh_q);
     _usbh_q = NULL;
 
-    #if OSAL_MUTEX_REQUIRED
+  #if CFG_TUH_HUB
+    osal_queue_delete(_usbh_daq);
+    _usbh_daq = NULL;
+  #endif
+
+  #if OSAL_MUTEX_REQUIRED
     // TODO make sure there is no task waiting on this mutex
     osal_mutex_delete(_usbh_mutex);
     _usbh_mutex = NULL;
-    #endif
+  #endif
   }
 
   return true;
@@ -570,9 +608,19 @@ bool tuh_deinit(uint8_t rhport) {
 
 bool tuh_task_event_ready(void) {
   if (!tuh_inited()) {
-    return false; // Skip if stack is not initialized
+    return false; // Skip if tusb stack is not initialized
   }
-  return !osal_queue_empty(_usbh_q);
+  if (!osal_queue_empty(_usbh_q)) {
+    return true;
+  }
+
+  #if CFG_TUH_HUB
+  if (!osal_queue_empty(_usbh_daq)) {
+    return true;
+  }
+  #endif
+
+  return false;
 }
 
 /* USB Host Driver task
@@ -592,51 +640,87 @@ bool tuh_task_event_ready(void) {
     @endcode
  */
 void tuh_task_ext(uint32_t timeout_ms, bool in_isr) {
-  (void) in_isr; // not implemented yet
-
   // Skip if stack is not initialized
   if (!tuh_inited()) {
     return;
   }
 
+  (void) in_isr; // not implemented yet
+
   // Loop until there are no more events in the queue or CFG_TUH_TASK_EVENTS_PER_RUN is reached
   for (unsigned epr = 0;; epr++) {
-#if CFG_TUH_TASK_EVENTS_PER_RUN > 0
+  #if CFG_TUH_TASK_EVENTS_PER_RUN > 0
     if (epr >= CFG_TUH_TASK_EVENTS_PER_RUN) {
       TU_LOG_USBH("USBH event limit (" TU_XSTRING(CFG_TUH_TASK_EVENTS_PER_RUN) ") reached\r\n");
       break;
     }
-#endif
+  #endif
+
+    // Process call_after_ms function if ms is reached
+    tusb_defer_func_t after_cb = _usbh_data.call_after.func;
+    if (after_cb) {
+      int32_t remain_ms = (int32_t)(_usbh_data.call_after.at_ms - tusb_time_millis_api());
+      if (remain_ms <= 0) {
+        // delay expired, run callback now
+        TU_LOG_USBH("USBH invoke scheduled function\r\n");
+        _usbh_data.call_after.func = NULL;
+        after_cb(_usbh_data.call_after.arg);
+      }
+
+      // above after_cb() can re-schedule another function, we need to re-check and reduce timeout of
+      // the main event timeout to make sure we aren't blocking more than call_after remaining ms.
+      if (_usbh_data.call_after.func != NULL) {
+        remain_ms = (int32_t) (_usbh_data.call_after.at_ms - tusb_time_millis_api());
+        if (remain_ms <= 0) {
+          timeout_ms = 0; // expired already
+        } else if (timeout_ms > (uint32_t)remain_ms) {
+          timeout_ms = (uint32_t)remain_ms;
+        }
+      }
+    }
+
     hcd_event_t event;
-    if (!osal_queue_receive(_usbh_q, &event, timeout_ms)) { return; }
+
+  #if CFG_TUH_HUB
+    // Get deferred device attachments if none is enumerating
+    bool has_deferred_attach = false;
+    if (_usbh_data.enumerating_daddr == TUSB_INDEX_INVALID_8) {
+      // zero wait to avoid blocking the main event queue
+      has_deferred_attach = osal_queue_receive(_usbh_daq, &event, 0);
+    }
+
+    if (!has_deferred_attach) // skip event queue to process deferred attach
+  #endif
+    {
+      if (!osal_queue_receive(_usbh_q, &event, timeout_ms)) {
+        return;
+      }
+    }
 
     switch (event.event_id) {
       case HCD_EVENT_DEVICE_ATTACH:
         // Should we miss the hub detach event due to high traffic, Or due to physical debouncing, some devices can
-        // cause multiple attaches (actually reset) without detach event.
+        // cause multiple attaches (actually reset) without a detached event.
         // Force remove currently mounted with the same bus info (rhport, hub addr, hub port) if exists
         process_remove_event(&event);
 
         // due to the shared control buffer, we must fully complete enumerating one device first.
-        // TODO better to have an separated queue for newly attached devices
         if (_usbh_data.enumerating_daddr == TUSB_INDEX_INVALID_8) {
           // New device attached and we are ready
           TU_LOG_USBH("[%u:] USBH Device Attach\r\n", event.rhport);
           _usbh_data.enumerating_daddr = 0; // enumerate new device with address 0
           enum_new_device(&event);
-        } else {
-          // currently enumerating another device
+        }
+  #if CFG_TUH_HUB
+        else {
           TU_LOG_USBH("[%u:] USBH Defer Attach until current enumeration complete\r\n", event.rhport);
-          const bool is_empty = osal_queue_empty(_usbh_q);
-          queue_event(&event, in_isr);
-          if (is_empty) {
-            return; // Exit if this is the only event in the queue, otherwise we loop forever
-          }
+          TU_ASSERT(osal_queue_send(_usbh_daq, &event, in_isr), );
         }
+  #endif
         break;
 
       case HCD_EVENT_DEVICE_REMOVE:
-        TU_LOG_USBH("[%u:%u:%u] USBH DEVICE REMOVED\r\n", event.rhport, event.connection.hub_addr, event.connection.hub_port);
+        TU_LOG_USBH("[%u:%u:%u] USBH Device Removed\r\n", event.rhport, event.connection.hub_addr, event.connection.hub_port);
         process_remove_event(&event);
         break;
 
@@ -709,10 +793,8 @@ void tuh_task_ext(uint32_t timeout_ms, bool in_isr) {
         break;
     }
 
-#if CFG_TUSB_OS != OPT_OS_NONE && CFG_TUSB_OS != OPT_OS_PICO
-    // return if there is no more events, for application to run other background
-    if (osal_queue_empty(_usbh_q)) return;
-#endif
+    // allow to exit tuh_task() if there is no event in the next run
+    timeout_ms = 0;
   }
 }
 
@@ -770,10 +852,8 @@ bool tuh_control_xfer (tuh_xfer_t* xfer) {
 
     while (result == XFER_RESULT_INVALID) {
       // Note: this can be called within an callback ie. part of tuh_task()
-      // therefore event with RTOS tuh_task() still need to be invoked
-      if (tuh_task_event_ready()) {
-        tuh_task();
-      }
+      // therefore even with RTOS tuh_task_ext() still need to be invoked
+      tuh_task_ext(0, false);
       // TODO probably some timeout to prevent hanged
     }
 
@@ -1423,10 +1503,10 @@ enum {                                      // USB 2.0 specs 7.1.7 for timing
 enum {
   ENUM_IDLE,
   ENUM_HUB_RERSET,
-  ENUM_HUB_GET_STATUS_AFTER_RESET,
+  ENUM_HUB_RESET_COMPLETE,
   ENUM_HUB_CLEAR_RESET,
+  ENUM_HUB_CLEAR_RESET_RETRY, // 2nd attempt waiting for hub reset
   ENUM_HUB_CLEAR_RESET_COMPLETE,
-
   ENUM_ADDR0_DEVICE_DESC,
   ENUM_SET_ADDR,
   ENUM_GET_DEVICE_DESC,
@@ -1445,104 +1525,139 @@ enum {
 };
 
 static uint8_t enum_get_new_address(bool is_hub);
-static bool enum_parse_configuration_desc (uint8_t dev_addr, tusb_desc_configuration_t const* desc_cfg);
-static void enum_full_complete(bool success);
-static void process_enumeration(tuh_xfer_t* xfer);
+static bool    enum_parse_configuration_desc(uint8_t dev_addr, const tusb_desc_configuration_t *desc_cfg);
+static void    enum_full_complete(bool success);
+static void    process_enumeration(tuh_xfer_t *xfer);
 
-// start a new enumeration process
-static bool enum_new_device(hcd_event_t* event) {
-  tuh_bus_info_t* dev0_bus = &_usbh_data.dev0_bus;
-  dev0_bus->rhport = event->rhport;
-  dev0_bus->hub_addr = event->connection.hub_addr;
-  dev0_bus->hub_port = event->connection.hub_port;
+enum {
+  ENUM_AFTER_DEBOUNCING_DELAY,
+  ENUM_AFTER_RESET_ROOT_DELAY,
+  ENUM_AFTER_RESET_ROOT_POST_DELAY,
+  ENUM_AFTER_RESET_HUB_DELAY,
+  ENUM_AFTER_RESET_HUB_DELAY_RETRY,
+  ENUM_AFTER_RESET_RECOVERY_DELAY,
+  ENUM_AFTER_SET_ADDRESS_RECOVERY_DELAY,
+};
 
-  // wait until device connection is stable TODO non blocking
-  tusb_time_delay_ms_api(ENUM_DEBOUNCING_DELAY_MS);
+// process async delay in enumeration
+static void enum_delay_async(uintptr_t state) {
+  tuh_bus_info_t *dev0_bus = &_usbh_data.dev0_bus;
+  switch (state) {
+    case ENUM_AFTER_DEBOUNCING_DELAY:
+  #if CFG_TUH_HUB
+      if (dev0_bus->hub_addr != 0) {
+        // connected via hub
+        TU_VERIFY(dev0_bus->hub_port != 0, );
+        TU_ASSERT(hub_port_get_status(dev0_bus->hub_addr, dev0_bus->hub_port, NULL, process_enumeration,
+                                      ENUM_HUB_RERSET), );
+      } else
+  #endif
+      {
+        // connected directly to roothub
+        _usbh_data.attach_debouncing_bm &= (uint8_t)~TU_BIT(dev0_bus->rhport); // clear roothub debouncing delay
+        if (!hcd_port_connect_status(dev0_bus->rhport)) {
+          TU_LOG_USBH("Device unplugged while debouncing\r\n");
+          enum_full_complete(false);
+          return;
+        }
+        hcd_port_reset(dev0_bus->rhport); // reset port
+        usbh_defer_func_ms_async(ENUM_RESET_ROOT_DELAY_MS, enum_delay_async, ENUM_AFTER_RESET_ROOT_DELAY);
+      }
+      break;
 
-  if (dev0_bus->hub_addr == 0) {
-    // connected directly to roothub
-    // USB bus not active and frame number is not available yet.
-    // need to depend on tusb_time_millis_api() TODO non blocking
+    case ENUM_AFTER_RESET_ROOT_DELAY:
+      hcd_port_reset_end(dev0_bus->rhport);
+      usbh_defer_func_ms_async(ENUM_RESET_ROOT_POST_DELAY_MS, enum_delay_async, ENUM_AFTER_RESET_ROOT_POST_DELAY);
+      break;
 
-    _usbh_data.attach_debouncing_bm &= (uint8_t) ~TU_BIT(dev0_bus->rhport); // clear roothub debouncing delay
+    case ENUM_AFTER_RESET_ROOT_POST_DELAY:
+      if (!hcd_port_connect_status(dev0_bus->rhport)) {
+        // device unplugged while delaying
+        enum_full_complete(false);
+        return;
+      }
 
-    if (!hcd_port_connect_status(dev0_bus->rhport)) {
-      TU_LOG_USBH("Device unplugged while debouncing\r\n");
-      enum_full_complete(false);
-      return true;
-    }
+      dev0_bus->speed = hcd_port_speed_get(dev0_bus->rhport);
+      TU_LOG_USBH("%s Speed\r\n", tu_str_speed[dev0_bus->speed]);
 
-    // reset device
-    hcd_port_reset(dev0_bus->rhport);
-    tusb_time_delay_ms_api(ENUM_RESET_ROOT_DELAY_MS);
-    hcd_port_reset_end(dev0_bus->rhport);
-    tusb_time_delay_ms_api(ENUM_RESET_ROOT_POST_DELAY_MS);
+      // fake transfer to kick-off the enumeration process
+      tuh_xfer_t xfer;
+      xfer.daddr     = 0;
+      xfer.result    = XFER_RESULT_SUCCESS;
+      xfer.user_data = ENUM_ADDR0_DEVICE_DESC;
+      process_enumeration(&xfer);
+      break;
 
-    if (!hcd_port_connect_status(dev0_bus->rhport)) {
-      // device unplugged while delaying
-      enum_full_complete(false);
-      return true;
-    }
+  #if CFG_TUH_HUB
+    case ENUM_AFTER_RESET_HUB_DELAY:
+    case ENUM_AFTER_RESET_HUB_DELAY_RETRY:
+      // get status after reset complete to check for reset change
+      TU_ASSERT(hub_port_get_status(dev0_bus->hub_addr, dev0_bus->hub_port, NULL, process_enumeration,
+                                    state == ENUM_AFTER_RESET_HUB_DELAY ? ENUM_HUB_CLEAR_RESET
+                                                                        : ENUM_HUB_CLEAR_RESET_RETRY), );
+      break;
+  #endif
 
-    dev0_bus->speed = hcd_port_speed_get(dev0_bus->rhport);
-    TU_LOG_USBH("%s Speed\r\n", tu_str_speed[dev0_bus->speed]);
+    case ENUM_AFTER_RESET_RECOVERY_DELAY:
+      // TODO probably doesn't need to open/close each enumeration
+      if (!usbh_edpt_control_open(0, 8)) {
+        TU_LOG_USBH("Failed to open dev0's control endpoint\r\n");
+        enum_full_complete(false); // Stop enumeration gracefully
+        return;
+      }
+      // Get first 8 bytes of device descriptor for control endpoint size
+      TU_LOG_USBH("Get 8 byte of Device Descriptor\r\n");
+      TU_ASSERT(tuh_descriptor_get_device(0, _usbh_epbuf.ctrl, 8, process_enumeration, ENUM_SET_ADDR), );
+      break;
 
-    // fake transfer to kick-off the enumeration process
-    tuh_xfer_t xfer;
-    xfer.daddr = 0;
-    xfer.result = XFER_RESULT_SUCCESS;
-    xfer.user_data = ENUM_ADDR0_DEVICE_DESC;
-    process_enumeration(&xfer);
-  }
-  #if CFG_TUH_HUB
-  else {
-    // connected via hub
-    TU_VERIFY(dev0_bus->hub_port != 0);
-    TU_ASSERT(hub_port_get_status(dev0_bus->hub_addr, dev0_bus->hub_port, NULL,
-                                  process_enumeration, ENUM_HUB_RERSET));
+    case ENUM_AFTER_SET_ADDRESS_RECOVERY_DELAY: {
+      const uint8_t  new_addr = _usbh_data.enumerating_daddr;
+      usbh_device_t *new_dev  = get_device(new_addr);
+      TU_ASSERT(new_dev, );
+      if (!usbh_edpt_control_open(new_addr, new_dev->bMaxPacketSize0)) {
+        TU_LOG_USBH("Failed to open new device's control endpoint\r\n");
+        clear_device(new_dev);
+        enum_full_complete(false);
+        return;
+      }
+      TU_LOG_USBH("Get Device Descriptor\r\n");
+      TU_ASSERT(tuh_descriptor_get_device(new_addr, _usbh_epbuf.ctrl, sizeof(tusb_desc_device_t), process_enumeration,
+                                          ENUM_GET_STRING_LANGUAGE_ID_LEN), );
+      break;
+    }
+
+    default:
+      break;
   }
-  #endif // hub
+}
 
-  return true;
+// start a new enumeration process
+static void enum_new_device(hcd_event_t *event) {
+  tuh_bus_info_t *dev0_bus = &_usbh_data.dev0_bus;
+  dev0_bus->rhport         = event->rhport;
+  dev0_bus->hub_addr       = event->connection.hub_addr;
+  dev0_bus->hub_port       = event->connection.hub_port;
+  usbh_defer_func_ms_async(ENUM_DEBOUNCING_DELAY_MS, enum_delay_async, ENUM_AFTER_DEBOUNCING_DELAY);
 }
 
 // process device enumeration
-static void process_enumeration(tuh_xfer_t* xfer) {
-  // Retry a few times while enumerating since device can be unstable when starting up
-  static uint8_t failed_count = 0;
+static void process_enumeration(tuh_xfer_t *xfer) {
   if (XFER_RESULT_FAILED == xfer->result) {
-    enum {
-      ATTEMPT_COUNT_MAX = 3,
-      ATTEMPT_DELAY_MS = 100
-    };
-
-    // retry if not reaching max attempt
-    failed_count++;
-    bool retry = (_usbh_data.enumerating_daddr != TUSB_INDEX_INVALID_8) && (failed_count < ATTEMPT_COUNT_MAX);
-    if (retry) {
-      tusb_time_delay_ms_api(ATTEMPT_DELAY_MS); // delay a bit
-      TU_LOG_USBH("Enumeration attempt %u/%u\r\n", failed_count+1, ATTEMPT_COUNT_MAX);
-      retry = tuh_control_xfer(xfer);
-    }
-
-    if (!retry) {
-      enum_full_complete(false); // complete as failed
-    }
+    enum_full_complete(false); // failed to enum
     return;
   }
-  failed_count = 0;
 
-  uint8_t const daddr = xfer->daddr;
-  uintptr_t const state = xfer->user_data;
-  usbh_device_t* dev = get_device(daddr);
-  tuh_bus_info_t* dev0_bus = &_usbh_data.dev0_bus;
+  const uint8_t   daddr    = xfer->daddr;
+  const uintptr_t state    = xfer->user_data;
+  usbh_device_t  *dev      = get_device(daddr);
+  tuh_bus_info_t *dev0_bus = &_usbh_data.dev0_bus;
   if (daddr > 0) {
     TU_ASSERT(dev != NULL,);
   }
   uint16_t langid = 0x0409; // default is English
 
   switch (state) {
-    #if CFG_TUH_HUB
+  #if CFG_TUH_HUB
     case ENUM_HUB_RERSET: {
       hub_port_status_response_t port_status;
       hub_port_get_status_local(dev0_bus->hub_addr, dev0_bus->hub_port, &port_status);
@@ -1553,30 +1668,31 @@ static void process_enumeration(tuh_xfer_t* xfer) {
         return;
       }
 
-      TU_ASSERT(hub_port_reset(dev0_bus->hub_addr, dev0_bus->hub_port, process_enumeration, ENUM_HUB_GET_STATUS_AFTER_RESET),);
+      TU_ASSERT(hub_port_reset(dev0_bus->hub_addr, dev0_bus->hub_port, process_enumeration, ENUM_HUB_RESET_COMPLETE), );
       break;
     }
 
-    case ENUM_HUB_GET_STATUS_AFTER_RESET: {
-      tusb_time_delay_ms_api(ENUM_RESET_HUB_DELAY_MS); // wait for reset to take effect
-
-      // get status to check for reset change
-      TU_ASSERT(hub_port_get_status(dev0_bus->hub_addr, dev0_bus->hub_port, NULL, process_enumeration, ENUM_HUB_CLEAR_RESET),);
+    case ENUM_HUB_RESET_COMPLETE:
+      // wait for reset to take effect
+      usbh_defer_func_ms_async(ENUM_RESET_HUB_DELAY_MS, enum_delay_async, ENUM_AFTER_RESET_HUB_DELAY);
       break;
-    }
 
-    case ENUM_HUB_CLEAR_RESET: {
+    case ENUM_HUB_CLEAR_RESET:
+    case ENUM_HUB_CLEAR_RESET_RETRY: {
       hub_port_status_response_t port_status;
       hub_port_get_status_local(dev0_bus->hub_addr, dev0_bus->hub_port, &port_status);
 
       if (1 == port_status.change.reset) {
         // Acknowledge Port Reset Change
-        TU_ASSERT(hub_port_clear_reset_change(dev0_bus->hub_addr, dev0_bus->hub_port, process_enumeration, ENUM_HUB_CLEAR_RESET_COMPLETE),);
+        TU_ASSERT(hub_port_clear_reset_change(dev0_bus->hub_addr, dev0_bus->hub_port, process_enumeration,
+                                              ENUM_HUB_CLEAR_RESET_COMPLETE), );
+      } else if (state == ENUM_HUB_CLEAR_RESET) {
+        // retry one more time if reset change not set yet
+        usbh_defer_func_ms_async(ENUM_RESET_HUB_DELAY_MS, enum_delay_async, ENUM_AFTER_RESET_HUB_DELAY_RETRY);
       } else {
-        // maybe retry if reset change not set but we need timeout to prevent infinite loop
-        // TU_ASSERT(hub_port_get_status(dev0_bus->hub_addr, dev0_bus->hub_port, NULL, process_enumeration, ENUM_HUB_CLEAR_RESET_COMPLETE),);
+        // retry but still not set --> failed
+        enum_full_complete(false);
       }
-
       break;
     }
 
@@ -1590,30 +1706,17 @@ static void process_enumeration(tuh_xfer_t* xfer) {
         return;
       }
 
-      dev0_bus->speed = (port_status.status.high_speed) ? TUSB_SPEED_HIGH :
-                        (port_status.status.low_speed) ? TUSB_SPEED_LOW : TUSB_SPEED_FULL;
+      dev0_bus->speed = (port_status.status.high_speed)  ? TUSB_SPEED_HIGH
+                        : (port_status.status.low_speed) ? TUSB_SPEED_LOW
+                                                         : TUSB_SPEED_FULL;
 
       TU_ATTR_FALLTHROUGH;
     }
-    #endif
-
-    case ENUM_ADDR0_DEVICE_DESC: {
-      tusb_time_delay_ms_api(ENUM_RESET_RECOVERY_DELAY_MS); // reset recovery
-
-      // TODO probably doesn't need to open/close each enumeration
-      uint8_t const addr0 = 0;
-      if (!usbh_edpt_control_open(addr0, 8)) {
-        // Stop enumeration gracefully
-        enum_full_complete(false);
-        TU_ASSERT(false,);
-      }
+  #endif
 
-      // Get first 8 bytes of device descriptor for control endpoint size
-      TU_LOG_USBH("Get 8 byte of Device Descriptor\r\n");
-      TU_ASSERT(tuh_descriptor_get_device(addr0, _usbh_epbuf.ctrl, 8,
-                                          process_enumeration, ENUM_SET_ADDR),);
+    case ENUM_ADDR0_DEVICE_DESC:
+      usbh_defer_func_ms_async(ENUM_RESET_RECOVERY_DELAY_MS, enum_delay_async, ENUM_AFTER_RESET_RECOVERY_DELAY);
       break;
-    }
 
     case ENUM_SET_ADDR: {
       const tusb_desc_device_t *desc_device = (const tusb_desc_device_t *) _usbh_epbuf.ctrl;
@@ -1625,31 +1728,19 @@ static void process_enumeration(tuh_xfer_t* xfer) {
       new_dev->connected = 1;
       new_dev->bMaxPacketSize0 = desc_device->bMaxPacketSize0;
 
-      TU_ASSERT(tuh_address_set(0, new_addr, process_enumeration, ENUM_GET_DEVICE_DESC),);
+      TU_ASSERT(tuh_address_set(0, new_addr, process_enumeration, ENUM_GET_DEVICE_DESC), );
       break;
     }
 
     case ENUM_GET_DEVICE_DESC: {
-      tusb_time_delay_ms_api(ENUM_SET_ADDRESS_RECOVERY_DELAY_MS); // set address recovery
-
-      const uint8_t new_addr = (uint8_t) tu_le16toh(xfer->setup->wValue);
-      usbh_device_t* new_dev = get_device(new_addr);
-      TU_ASSERT(new_dev,);
-      new_dev->addressed = 1;
+      const uint8_t  new_addr = (uint8_t)tu_le16toh(xfer->setup->wValue);
+      usbh_device_t *new_dev  = get_device(new_addr);
+      TU_ASSERT(new_dev, );
+      new_dev->addressed           = 1;
       _usbh_data.enumerating_daddr = new_addr;
 
       usbh_device_close(dev0_bus->rhport, 0); // close dev0
-
-      if (!usbh_edpt_control_open(new_addr, new_dev->bMaxPacketSize0)) { // open new control endpoint
-        // Stop enumeration gracefully
-        clear_device(new_dev);
-        enum_full_complete(false);
-        TU_ASSERT(false,);
-      }
-
-      TU_LOG_USBH("Get Device Descriptor\r\n");
-      TU_ASSERT(tuh_descriptor_get_device(new_addr, _usbh_epbuf.ctrl, sizeof(tusb_desc_device_t),
-                                          process_enumeration, ENUM_GET_STRING_LANGUAGE_ID_LEN),);
+      usbh_defer_func_ms_async(ENUM_SET_ADDRESS_RECOVERY_DELAY_MS, enum_delay_async, ENUM_AFTER_SET_ADDRESS_RECOVERY_DELAY);
       break;
     }
 
@@ -1799,11 +1890,12 @@ static void process_enumeration(tuh_xfer_t* xfer) {
       TU_LOG_USBH("Device configured\r\n");
       dev->configured = 1;
 
-    #if CFG_TUH_HUB
+  #if CFG_TUH_HUB
+      // get next hub status now since device can be unplugged before set_configure() is complete
       if (_usbh_data.dev0_bus.hub_addr != 0) {
-        hub_edpt_status_xfer(_usbh_data.dev0_bus.hub_addr); // get next hub status
+        hub_edpt_status_xfer(_usbh_data.dev0_bus.hub_addr);
       }
-    #endif
+  #endif
 
       // Parse configuration & set up drivers
       // driver_open() must not make any usb transfer
@@ -1858,10 +1950,10 @@ static bool enum_parse_configuration_desc(uint8_t dev_addr, tusb_desc_configurat
 
   TU_LOG_USBH("Parsing Configuration descriptor (wTotalLength = %u)\r\n", total_len);
 
-  // parse each interfaces
+  // parse all interfaces
   while (tu_desc_in_bounds(p_desc, desc_end)) {
     if (0 == tu_desc_len(p_desc)) {
-      // A zero length descriptor indicates that the device is off spec (e.g. wrong wTotalLength).
+      // A zero-length descriptor indicates that the device is off spec (e.g. wrong wTotalLength).
       // Parsed interfaces should still be usable
       TU_LOG_USBH("Encountered a zero-length descriptor after %" PRIu32 " bytes\r\n", (uint32_t)p_desc - (uint32_t)desc_cfg);
       break;
@@ -1877,7 +1969,7 @@ static bool enum_parse_configuration_desc(uint8_t dev_addr, tusb_desc_configurat
     // uint16_t const drv_len = tu_desc_get_interface_total_len(desc_itf, assoc_itf_count, (uint16_t)
     // (desc_end-p_desc)); TU_ASSERT(drv_len >= sizeof(tusb_desc_interface_t));
 
-    // Find driver for this interface
+    // Find a driver for this interface
     const uint16_t remaining_len = (uint16_t)(desc_end - p_desc);
     uint8_t        drv_id;
     for (drv_id = 0; drv_id < TOTAL_DRIVER_COUNT; drv_id++) {
@@ -1925,7 +2017,7 @@ void usbh_driver_set_config_complete(uint8_t dev_addr, uint8_t itf_num) {
     }
   }
 
-  // all interface are configured
+  // all interfaces are configured
   if (itf_num == CFG_TUH_INTERFACE_MAX) {
     enum_full_complete(true);
 
@@ -1940,16 +2032,17 @@ void usbh_driver_set_config_complete(uint8_t dev_addr, uint8_t itf_num) {
 
 static void enum_full_complete(bool success) {
   (void)success;
-  // mark enumeration as complete
-  _usbh_data.enumerating_daddr = TUSB_INDEX_INVALID_8;
+  TU_LOG_USBH("Enumeration complete: success = %u\r\n", success);
 
-#if CFG_TUH_HUB
+  _usbh_data.enumerating_daddr = TUSB_INDEX_INVALID_8; // mark enumeration as complete
+  _usbh_data.call_after.func = NULL;
+
+  #if CFG_TUH_HUB
   // Hub status is already requested in case of successful enumeration
-  if (_usbh_data.dev0_bus.hub_addr != 0 && !success) {
-    hub_edpt_status_xfer(_usbh_data.dev0_bus.hub_addr); // get next hub status
+  if (!success && _usbh_data.dev0_bus.hub_addr != 0) {
+    hub_edpt_status_xfer(_usbh_data.dev0_bus.hub_addr);
   }
-#endif
-
+  #endif
 }
 
 #endif
diff --git a/src/host/usbh_pvt.h b/src/host/usbh_pvt.h
index 57428e3c5..adb6a8c44 100644
--- a/src/host/usbh_pvt.h
+++ b/src/host/usbh_pvt.h
@@ -68,8 +68,12 @@ uint8_t* usbh_get_enum_buf(void);
 
 void usbh_int_set(bool enabled);
 
+// Invoke this function later in tuh_task() by putting it into task queue
 void usbh_defer_func(osal_task_func_t func, void *param, bool in_isr);
 
+// Schedules a function to be called after certain time asynchronously
+bool usbh_defer_func_ms_async(uint32_t ms, tusb_defer_func_t func, uintptr_t param);
+
 void usbh_spin_lock(bool in_isr);
 void usbh_spin_unlock(bool in_isr);