fixed bandwidth overage detection (#71)

The check for the amount of byte transferred in one frame time was done
before the update of the vertical pointer in the current Queue of the
last executed TD. Therefore, on the next frame time, the last executed
TD was being "executed" again. The check has now been moved to the top
of the loop.

bochs/iodev/usb/uhci_core.cc

@@ -676,6 +676,14 @@ void bx_uhci_core_c::uhci_timer(void)
 
     // start the loop. we allow USB_UHCI_LOOP_COUNT queues to be processed
     while (count--) {
+      // The UHCI (USB 1.1) only allows so many bytes to be transfered per frame.
+      // Due to control/bulk reclamation, we need to catch this and stop transferring 
+      //  or this code will just keep processing TDs.
+      if (bytes_processed >= hub.max_bandwidth) {
+        BX_DEBUG(("Process Bandwidth Limits for this frame (%d with a limit of %d).", bytes_processed, hub.max_bandwidth));
+        break;
+      }
+
       if (!USB_UHCI_IS_LINK_VALID(item))  // the the T bit is set, we are done
         break;
 
@@ -750,15 +758,7 @@ void bx_uhci_core_c::uhci_timer(void)
 
           // we processed another td within this queue line
           td_count++;
-
-          // The UHCI (USB 1.1) only allows so many bytes to be transfered per frame.
-          // Due to control/bulk reclamation, we need to catch this and stop transferring 
-          //  or this code will just keep processing TDs.
           bytes_processed += r_actlen;
-          if (bytes_processed >= hub.max_bandwidth) {
-            BX_DEBUG(("Process Bandwidth Limits for this frame (%d with a limit of %d).", bytes_processed, hub.max_bandwidth));
-            break;
-          }
 
           // move to the next item
           if (!was_stall) {
@@ -1028,7 +1028,7 @@ void bx_uhci_core_c::set_status(struct TD *td, bool stalled, bool data_buffer_er
   td->dword1 |= bitstuff_error    ? (1<<17) : 0; // bitstuff error
   td->dword1 |= (act_len & 0x7FF);               // actual length
   if (stalled || data_buffer_error || babble || crc_time_out || bitstuff_error)
-    td->dword1 &= ~((1<<28) | (1<<27));  // clear the c_err field in there was an error
+    td->dword1 &= ~((1<<28) | (1<<27));  // clear the c_err field if there was an error
 }