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path: root/drivers/usb/dwc3/gadget.c
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Diffstat (limited to 'drivers/usb/dwc3/gadget.c')
-rw-r--r--drivers/usb/dwc3/gadget.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 520031ba38aa..183b90923f51 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1291,6 +1291,19 @@ static void __dwc3_prepare_one_trb(struct dwc3_ep *dep, struct dwc3_trb *trb,
if (usb_endpoint_xfer_bulk(dep->endpoint.desc) && dep->stream_capable)
trb->ctrl |= DWC3_TRB_CTRL_SID_SOFN(stream_id);
+ /*
+ * As per data book 4.2.3.2TRB Control Bit Rules section
+ *
+ * The controller autonomously checks the HWO field of a TRB to determine if the
+ * entire TRB is valid. Therefore, software must ensure that the rest of the TRB
+ * is valid before setting the HWO field to '1'. In most systems, this means that
+ * software must update the fourth DWORD of a TRB last.
+ *
+ * However there is a possibility of CPU re-ordering here which can cause
+ * controller to observe the HWO bit set prematurely.
+ * Add a write memory barrier to prevent CPU re-ordering.
+ */
+ wmb();
trb->ctrl |= DWC3_TRB_CTRL_HWO;
dwc3_ep_inc_enq(dep);