zephyr: keep the endpoint queues free during suspend

c2usb/port/zephyr/udc_mac.cpp

@@ -368,13 +368,15 @@ int udc_mac::process_event(const udc_event& event)
         process_ep_event(event.buf);
         break;
     case UDC_EVT_RESET:
+        cancel_all_transfers();
         bus_reset();
         break;
     case UDC_EVT_SUSPEND:
         set_power_state(power::state::L2_SUSPEND);
         break;
     case UDC_EVT_RESUME:
     case UDC_EVT_VBUS_READY:
+        cancel_all_transfers();
         set_power_state(power::state::L0_ON);
         break;
     case UDC_EVT_VBUS_REMOVED:
@@ -583,6 +585,19 @@ usb::endpoint::address udc_mac::ep_handle_to_address(ep_handle eph) const
     return endpoint::address(udc_get_buf_info(ep_handle_to_buf(eph))->ep);
 }
 
+void udc_mac::cancel_all_transfers()
+{
+    for (auto* buf : ep_bufs_)
+    {
+        endpoint::address addr{udc_get_buf_info(buf)->ep};
+        if (busy_flags_.test(addr))
+        {
+            [[maybe_unused]] auto ret = udc_ep_dequeue(dev_, addr);
+            busy_flags_.clear(addr);
+        }
+    }
+}
+
 usb::df::ep_handle udc_mac::ep_open(const usb::df::config::endpoint& ep)
 {
     auto ret = udc_ep_enable(dev_, ep.address(), ep.bmAttributes, ep.wMaxPacketSize, ep.bInterval);
@@ -611,7 +626,7 @@ usb::result udc_mac::ep_transfer(usb::df::ep_handle eph, const transfer& t, usb:
         return result::BUSY;
     }
 #endif
-    if (busy_flags_.test_and_set(addr))
+    if ((power_state() != power::state::L0_ON) or busy_flags_.test_and_set(addr))
     {
         return result::BUSY;
     }

c2usb/port/zephyr/udc_mac.hpp

@@ -84,6 +84,7 @@ class udc_mac : public df::mac
     usb::result ep_clear_stall(endpoint::address addr);
     usb::result ep_transfer(usb::df::ep_handle eph, const usb::df::transfer& t, usb::direction dir);
 
+    void cancel_all_transfers();
     usb::df::ep_handle ep_open(const usb::df::config::endpoint& ep) override;
     usb::result ep_send(usb::df::ep_handle eph, const std::span<const uint8_t>& data) override;
     usb::result ep_receive(usb::df::ep_handle eph, const std::span<uint8_t>& data) override;