diff options
Diffstat (limited to 'drivers/usb/dwc3/gadget.c')
| -rw-r--r-- | drivers/usb/dwc3/gadget.c | 13 |
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); |