usb: dwc3: workaround: missing disconnect event

DWC3 revisions <1.88a have an issue which would
case a missing Disconnect event if cable is
disconnected while there's a Setup packet
pending the FIFO.

Signed-off-by: Felipe Balbi <balbi@ti.com>

3 files changed, 37 insertions, 0 deletions

diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index b901a4d3b068..836cf9942a4f 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -578,6 +578,7 @@ struct dwc3_hwparams {
  * @ep0_bounced: true when we used bounce buffer
  * @ep0_expect_in: true when we expect a DATA IN transfer
  * @start_config_issued: true when StartConfig command has been issued
+ * @setup_packet_pending: true when there's a Setup Packet in FIFO. Workaround
  * @ep0_next_event: hold the next expected event
  * @ep0state: state of endpoint zero
  * @link_state: link state
@@ -633,6 +634,7 @@ struct dwc3 {
         unsigned                ep0_bounced:1;
         unsigned                ep0_expect_in:1;
         unsigned                start_config_issued:1;
+        unsigned                setup_packet_pending:1;
         unsigned                delayed_status:1;
 
         enum dwc3_ep0_next      ep0_next_event;
diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
index 314acb289d23..ed44525c8d62 100644
--- a/drivers/usb/dwc3/ep0.c
+++ b/drivers/usb/dwc3/ep0.c
@@ -625,6 +625,7 @@ static void dwc3_ep0_xfer_complete(struct dwc3 *dwc,
         struct dwc3_ep          *dep = dwc->eps[event->endpoint_number];
 
         dep->flags &= ~DWC3_EP_BUSY;
+        dwc->setup_packet_pending = false;
 
         switch (dwc->ep0state) {
         case EP0_SETUP_PHASE:
@@ -726,6 +727,8 @@ static void dwc3_ep0_do_control_status(struct dwc3 *dwc, u32 epnum)
 static void dwc3_ep0_xfernotready(struct dwc3 *dwc,
                 const struct dwc3_event_depevt *event)
 {
+        dwc->setup_packet_pending = true;
+
         /*
          * This part is very tricky: If we has just handled
          * XferNotReady(Setup) and we're now expecting a
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 6704a52c9f12..7c98b3f2e6a7 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1640,6 +1640,7 @@ static void dwc3_gadget_disconnect_interrupt(struct dwc3 *dwc)
         dwc->start_config_issued = false;
 
         dwc->gadget.speed = USB_SPEED_UNKNOWN;
+        dwc->setup_packet_pending = false;
 }
 
 static void dwc3_gadget_usb3_phy_power(struct dwc3 *dwc, int on)
@@ -1676,6 +1677,37 @@ static void dwc3_gadget_reset_interrupt(struct dwc3 *dwc)
 
         dev_vdbg(dwc->dev, "%s\n", __func__);
 
+        /*
+         * WORKAROUND: DWC3 revisions <1.88a have an issue which
+         * would cause a missing Disconnect Event if there's a
+         * pending Setup Packet in the FIFO.
+         *
+         * There's no suggested workaround on the official Bug
+         * report, which states that "unless the driver/application
+         * is doing any special handling of a disconnect event,
+         * there is no functional issue".
+         *
+         * Unfortunately, it turns out that we _do_ some special
+         * handling of a disconnect event, namely complete all
+         * pending transfers, notify gadget driver of the
+         * disconnection, and so on.
+         *
+         * Our suggested workaround is to follow the Disconnect
+         * Event steps here, instead, based on a setup_packet_pending
+         * flag. Such flag gets set whenever we have a XferNotReady
+         * event on EP0 and gets cleared on XferComplete for the
+         * same endpoint.
+         *
+         * Refers to:
+         *
+         * STAR#9000466709: RTL: Device : Disconnect event not
+         * generated if setup packet pending in FIFO
+         */
+        if (dwc->revision < DWC3_REVISION_188A) {
+                if (dwc->setup_packet_pending)
+                        dwc3_gadget_disconnect_interrupt(dwc);
+        }
+
         /* Enable PHYs */
         dwc3_gadget_usb2_phy_power(dwc, true);
         dwc3_gadget_usb3_phy_power(dwc, true);