usb: dwc3: gadget: Allow restarting a transfer
It's possible that there's no new TRBs prepared when kicking a transfer.
This happens when we need to stop and restart a transfer such as in the
case of reinitiating a stream or retrying isoc transfer. For streams,
sometime host may reject a stream and the device may need to reinitiate
that stream by stopping and restarting a transfer. In this case, all the
TRBs may have already been prepared. Allow the function
__dwc3_gadget_kick_transfer() to go through even though there's no new
TRB.
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 359824c..76c383e 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1326,8 +1326,13 @@ static int __dwc3_gadget_kick_transfer(struct dwc3_ep *dep)
int ret;
u32 cmd;
+ /*
+ * Note that it's normal to have no new TRBs prepared (i.e. ret == 0).
+ * This happens when we need to stop and restart a transfer such as in
+ * the case of reinitiating a stream or retrying an isoc transfer.
+ */
ret = dwc3_prepare_trbs(dep);
- if (ret <= 0)
+ if (ret < 0)
return ret;
starting = !(dep->flags & DWC3_EP_TRANSFER_STARTED);