[PATCH v2] usb: xhci: fix lack of short packet event trb handling

[Ran Wang]

For bulk IN transfer, the codes will set ISP flag to request event TRB
being generated by xHC for case of short packet. So in
buffer-cross-64K-boundary case (which we will divide payload and enqueuqe
more than 1 transfer TRB), if the first TRB ends up with a short packet
condition it will trigger an short packet code transfer event per that
flag and cause more than 1 event TRB gegerated for this transfer.

However, current codes will only handle the first transfer event TRB
then mark current transfer completed, which causing next transfer
failure due to event TRB mis-match.

Such issue has been observed on some Layerscape platforms (LS1028A,
LS1088A, etc) with USB ethernet device

This patch adds a loop to make sure the event TRB for last transfer TRB
has been  handled in time.

Signed-off-by: Ran Wang <ran.wang_1 at nxp.com>
---
Change in v2:
 - Re-write commit message to describe context more clearly.
 - Add prefix 'le64_to_cpu' for 'event->trans_event.buffer'.

 drivers/usb/host/xhci-ring.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 13065d7..e0ccf01 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -580,10 +580,13 @@ int xhci_bulk_tx(struct usb_device *udev, unsigned long pipe,
 	int ret;
 	u32 trb_fields[4];
 	u64 val_64 = virt_to_phys(buffer);
+	void *last_transfer_trb_addr;
+	int available_length;
 
 	debug("dev=%p, pipe=%lx, buffer=%p, length=%d\n",
 		udev, pipe, buffer, length);
 
+	available_length = length;
 	ep_index = usb_pipe_ep_index(pipe);
 	virt_dev = ctrl->devs[slot_id];
 
@@ -697,7 +700,7 @@ int xhci_bulk_tx(struct usb_device *udev, unsigned long pipe,
 		trb_fields[2] = length_field;
 		trb_fields[3] = field | TRB_TYPE(TRB_NORMAL);
 
-		queue_trb(ctrl, ring, (num_trbs > 1), trb_fields);
+		last_transfer_trb_addr = queue_trb(ctrl, ring, (num_trbs > 1), trb_fields);
 
 		--num_trbs;
 
@@ -710,6 +713,7 @@ int xhci_bulk_tx(struct usb_device *udev, unsigned long pipe,
 
 	giveback_first_trb(udev, ep_index, start_cycle, start_trb);
 
+again:
 	event = xhci_wait_for_event(ctrl, TRB_TRANSFER);
 	if (!event) {
 		debug("XHCI bulk transfer timed out, aborting...\n");
@@ -718,12 +722,19 @@ int xhci_bulk_tx(struct usb_device *udev, unsigned long pipe,
 		udev->act_len = 0;
 		return -ETIMEDOUT;
 	}
-	field = le32_to_cpu(event->trans_event.flags);
 
+	if ((void *)le64_to_cpu(event->trans_event.buffer) != last_transfer_trb_addr) {
+		available_length -=
+			(int)EVENT_TRB_LEN(le32_to_cpu(event->trans_event.transfer_len));
+		xhci_acknowledge_event(ctrl);
+		goto again;
+	}
+
+	field = le32_to_cpu(event->trans_event.flags);
 	BUG_ON(TRB_TO_SLOT_ID(field) != slot_id);
 	BUG_ON(TRB_TO_EP_INDEX(field) != ep_index);
 
-	record_transfer_result(udev, event, length);
+	record_transfer_result(udev, event, available_length);
 	xhci_acknowledge_event(ctrl);
 	xhci_inval_cache((uintptr_t)buffer, length);
 
-- 
2.7.4