usb: dwc3: gadget: never pre-start Isochronous endpoints
We cannot pre-start isochronous endpoints because we
rely on the micro-frame number passed via
XferNotReady command for proper Isochronous
scheduling.
Fixes: 08a36b543803 ("usb: dwc3: gadget: simplify __dwc3_gadget_ep_queue()")
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 3c3ced1..f15147f 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1073,9 +1073,17 @@
list_add_tail(&req->list, &dep->pending_list);
- if (usb_endpoint_xfer_isoc(dep->endpoint.desc) &&
- dep->flags & DWC3_EP_PENDING_REQUEST) {
- if (list_empty(&dep->started_list)) {
+ /*
+ * NOTICE: Isochronous endpoints should NEVER be prestarted. We must
+ * wait for a XferNotReady event so we will know what's the current
+ * (micro-)frame number.
+ *
+ * Without this trick, we are very, very likely gonna get Bus Expiry
+ * errors which will force us issue EndTransfer command.
+ */
+ if (usb_endpoint_xfer_isoc(dep->endpoint.desc)) {
+ if ((dep->flags & DWC3_EP_PENDING_REQUEST) &&
+ list_empty(&dep->started_list)) {
dwc3_stop_active_transfer(dwc, dep->number, true);
dep->flags = DWC3_EP_ENABLED;
}