In cases where we're given an SG-list which is
longer than the amount of currently available TRBs,
we will be left with the same request on
started_list and we should prioritize that request
over possible new requests on pending_list. That's
a way to guarantee requests complete in order.
Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
---
drivers/usb/dwc3/gadget.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 84b449b17160..bca4150e3cf5 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1023,6 +1023,24 @@ static void dwc3_prepare_trbs(struct dwc3_ep *dep)
if (!dwc3_calc_trbs_left(dep))
return;
+ /*
+ * We can get in a situation where there's a request in the started list
+ * but there weren't enough TRBs to fully kick it in the first time
+ * around, so it has been waiting for more TRBs to be freed up.
+ *
+ * In that case, we should check if we have a request with pending_sgs
+ * in the started list and prepare TRBs for that request first,
+ * otherwise we will prepare TRBs completely out of order and that will
+ * break things.
+ */
+ list_for_each_entry(req, &dep->started_list, list) {
+ if (req->num_pending_sgs > 0)
+ dwc3_prepare_one_trb_sg(dep, req);
+
+ if (!dwc3_calc_trbs_left(dep))
+ return;
+ }
+
list_for_each_entry_safe(req, n, &dep->pending_list, list) {
if (req->num_pending_sgs > 0)
dwc3_prepare_one_trb_sg(dep, req);
--
2.10.1
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