WIP delay clearing EP_RX_ST

Avoid a race condition by delaying clearing EP_RX_ST on EP0 until the
packet buffer has been read.

Author: tlyu

system/GD32F30x_firmware/GD32F30x_usbd_library/device/Source/usbd_transc.c

@@ -35,6 +35,7 @@ OF SUCH DAMAGE.
 
 #include "usbd_enum.h"
 #include "usbd_transc.h"
+#include "usbd_lld_regs.h"
 
 /* local function prototypes ('static') */
 static inline void usb_stall_transc (usb_dev *udev);
@@ -56,8 +57,12 @@ void _usb_setup_transc (usb_dev *udev, uint8_t ep_num)
 
     usb_reqsta reqstat = REQ_NOTSUPP;
 
+    /* Force to IDLE state, to cancel actions by any pending completion handlers. */
+    udev->control.ctl_state = USBD_CTL_IDLE;
+
     uint16_t count = udev->drv_handler->ep_read((uint8_t *)(&udev->control.req), 0U, (uint8_t)EP_BUF_SNG);
 
+    USBD_EP_RX_ST_CLEAR(ep_num);
     if (count != USB_SETUP_PACKET_LEN) {
         udev->drv_handler->err(count);
         usb_stall_transc(udev);

system/GD32F30x_firmware/GD32F30x_usbd_library/usbd/Source/usbd_lld_int.c

@@ -118,7 +118,9 @@ void usbd_isr (void)
                 /* handle the USB OUT direction transaction */
                 if (USBD_EPxCS(ep_num) & EPxCS_RX_ST) {
                     /* clear successful receive interrupt flag */
-                    USBD_EP_RX_ST_CLEAR(ep_num);
+                    if (0U != ep_num) {
+                        USBD_EP_RX_ST_CLEAR(ep_num);
+                    }
 
                     if (USBD_EPxCS(ep_num) & EPxCS_SETUP) {
 
@@ -132,6 +134,10 @@ void usbd_isr (void)
 
                         uint16_t count = udev->drv_handler->ep_read (transc->xfer_buf, ep_num, (uint8_t)EP_BUF_SNG);
 
+                        if (0U == ep_num) {
+                            USBD_EP_RX_ST_CLEAR(ep_num);
+                        }
+
                         transc->xfer_buf += count;
                         transc->xfer_count += count;