dwc_otg: Fix a regression when dequeueing isochronous transfers

In 282bed9 (dwc_otg: make nak_holdoff work as intended with empty queues)
the dequeue mechanism was changed to leave FIQ-enabled transfers to run
to completion - to avoid leaving hub TT buffers with stale packets lying
around.

This broke FIQ-accelerated isochronous transfers, as this then meant that
dozens of transfers were performed after the dequeue function returned.

Restore the state machine fence for isochronous transfers.

drivers/usb/host/dwc_otg/dwc_otg_hcd.c

@@ -189,13 +189,21 @@ static void kill_urbs_in_qh_list(dwc_otg_hcd_t * hcd, dwc_list_link_t * qh_list)
 
  }
  if(qh->channel) {
+ int n = qh->channel->hc_num;
  /* Using hcchar.chen == 1 is not a reliable test.
  * It is possible that the channel has already halted
  * but not yet been through the IRQ handler.
  */
  if (fiq_fsm_enable && (hcd->fiq_state->channel[qh->channel->hc_num].fsm != FIQ_PASSTHROUGH)) {
+ local_fiq_disable();
+ fiq_fsm_spin_lock(&hcd->fiq_state->lock);
  qh->channel->halt_status = DWC_OTG_HC_XFER_URB_DEQUEUE;
  qh->channel->halt_pending = 1;
+ if (hcd->fiq_state->channel[n].fsm == FIQ_HS_ISOC_TURBO ||
+ hcd->fiq_state->channel[n].fsm == FIQ_HS_ISOC_SLEEPING)
+ hcd->fiq_state->channel[n].fsm = FIQ_HS_ISOC_ABORTED;
+ fiq_fsm_spin_unlock(&hcd->fiq_state->lock);
+ local_fiq_enable();
  } else {
  dwc_otg_hc_halt(hcd->core_if, qh->channel,
  DWC_OTG_HC_XFER_URB_DEQUEUE);
@@ -596,9 +604,15 @@ int dwc_otg_hcd_urb_dequeue(dwc_otg_hcd_t * hcd,
  /* In FIQ FSM mode, we need to shut down carefully.
  * The FIQ may attempt to restart a disabled channel */
  if (fiq_fsm_enable && (hcd->fiq_state->channel[n].fsm != FIQ_PASSTHROUGH)) {
+ local_fiq_disable();
+ fiq_fsm_spin_lock(&hcd->fiq_state->lock);
  qh->channel->halt_status = DWC_OTG_HC_XFER_URB_DEQUEUE;
  qh->channel->halt_pending = 1;
- //hcd->fiq_state->channel[n].fsm = FIQ_DEQUEUE_ISSUED;
+ if (hcd->fiq_state->channel[n].fsm == FIQ_HS_ISOC_TURBO ||
+ hcd->fiq_state->channel[n].fsm == FIQ_HS_ISOC_SLEEPING)
+ hcd->fiq_state->channel[n].fsm = FIQ_HS_ISOC_ABORTED;
+ fiq_fsm_spin_unlock(&hcd->fiq_state->lock);
+ local_fiq_enable();
  } else {
  dwc_otg_hc_halt(hcd->core_if, qh->channel,
  DWC_OTG_HC_XFER_URB_DEQUEUE);