avoid race condition enabling EP0 RX

Even if RX_ST is reset and EP0 is set to NAK, a Setup packet can still be received early. Don't enable receive if that happens, but instead let the next iteration of the ISR handle it.
keyboardio · Feb 24, 2023 · f1a815d · f1a815d
1 parent 2b78fc7
commit f1a815d
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/system/GD32F30x_firmware/GD32F30x_usbd_library/usbd/Source/usbd_lld_core.c b/system/GD32F30x_firmware/GD32F30x_usbd_library/usbd/Source/usbd_lld_core.c
@@ -374,6 +374,10 @@ static void usbd_ep_rx_enable (usb_dev *udev, uint8_t ep_addr)
 {
     (void)udev;
 
+    /* don't enable receive if a setup packet has come in */
+    if (0U == EP_ID(ep_addr) && (USBD_EPxCS(0U) & EPxCS_RX_ST)) {
+        return;
+    }
     /* enable endpoint to receive */
     USBD_EP_RX_STAT_SET(EP_ID(ep_addr), EPRX_VALID);
 }