usb: xhci: Add Clear_TT_Buffer

USB 2.0 specification chapter 11.17.5 says "as part of endpoint halt
processing for full-/low-speed endpoints connected via a TT, the host
software must use the Clear_TT_Buffer request to the TT to ensure
that the buffer is not in the busy state".

In our case, a full-speed speaker (ConferenceCam) is behind a high-
speed hub (ConferenceCam Connect), sometimes once we get STALL on a
request we may continue to get STALL with the folllowing requests,
like Set_Interface.

Here we invoke usb_hub_clear_tt_buffer() to send Clear_TT_Buffer
request to the hub of the device for the following Set_Interface
requests to the device to get ACK successfully.

Signed-off-by: Jim Lin <[e-mail]>
Acked-by: Mathias Nyman <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/host/xhci-ring.c

···
 	 * stream once the endpoint is on the HW schedule.
 	 */
 	if ((ep_state & EP_STOP_CMD_PENDING) || (ep_state & SET_DEQ_PENDING) ||
-	    (ep_state & EP_HALTED))
+	    (ep_state & EP_HALTED) || (ep_state & EP_CLEARING_TT))
 		return;
 	writel(DB_VALUE(ep_index, stream_id), db_addr);
 	/* The CPU has better things to do at this point than wait for a
···
 			xhci_ring_ep_doorbell(xhci, slot_id, ep_index,
 						stream_id);
 	}
+}
+
+void xhci_ring_doorbell_for_active_rings(struct xhci_hcd *xhci,
+		unsigned int slot_id,
+		unsigned int ep_index)
+{
+	ring_doorbell_for_active_rings(xhci, slot_id, ep_index);
 }
 
 /* Get the right ring for the given slot_id, ep_index and stream_id.
···
 	return NULL;
 }
 
+static void xhci_clear_hub_tt_buffer(struct xhci_hcd *xhci, struct xhci_td *td,
+		struct xhci_virt_ep *ep)
+{
+	/*
+	 * As part of low/full-speed endpoint-halt processing
+	 * we must clear the TT buffer (USB 2.0 specification 11.17.5).
+	 */
+	if (td->urb->dev->tt && !usb_pipeint(td->urb->pipe) &&
+	    (td->urb->dev->tt->hub != xhci_to_hcd(xhci)->self.root_hub) &&
+	    !(ep->ep_state & EP_CLEARING_TT)) {
+		ep->ep_state |= EP_CLEARING_TT;
+		td->urb->ep->hcpriv = td->urb->dev;
+		if (usb_hub_clear_tt_buffer(td->urb))
+			ep->ep_state &= ~EP_CLEARING_TT;
+	}
+}
+
 static void xhci_cleanup_halted_endpoint(struct xhci_hcd *xhci,
 		unsigned int slot_id, unsigned int ep_index,
 		unsigned int stream_id, struct xhci_td *td,
···
 	if (reset_type == EP_HARD_RESET) {
 		ep->ep_state |= EP_HARD_CLEAR_TOGGLE;
 		xhci_cleanup_stalled_ring(xhci, ep_index, stream_id, td);
+		xhci_clear_hub_tt_buffer(xhci, td, ep);
 	}
 	xhci_ring_cmd_db(xhci);
 }

drivers/usb/host/xhci.c

···
 }
 EXPORT_SYMBOL_GPL(xhci_gen_setup);
 
+static void xhci_clear_tt_buffer_complete(struct usb_hcd *hcd,
+		struct usb_host_endpoint *ep)
+{
+	struct xhci_hcd *xhci;
+	struct usb_device *udev;
+	unsigned int slot_id;
+	unsigned int ep_index;
+	unsigned long flags;
+
+	xhci = hcd_to_xhci(hcd);
+	udev = (struct usb_device *)ep->hcpriv;
+	slot_id = udev->slot_id;
+	ep_index = xhci_get_endpoint_index(&ep->desc);
+
+	spin_lock_irqsave(&xhci->lock, flags);
+	xhci->devs[slot_id]->eps[ep_index].ep_state &= ~EP_CLEARING_TT;
+	xhci_ring_doorbell_for_active_rings(xhci, slot_id, ep_index);
+	spin_unlock_irqrestore(&xhci->lock, flags);
+}
+
 static const struct hc_driver xhci_hc_driver = {
 	.description =		"xhci-hcd",
 	.product_desc =		"xHCI Host Controller",
···
 	.enable_usb3_lpm_timeout =	xhci_enable_usb3_lpm_timeout,
 	.disable_usb3_lpm_timeout =	xhci_disable_usb3_lpm_timeout,
 	.find_raw_port_number =	xhci_find_raw_port_number,
+	.clear_tt_buffer_complete = xhci_clear_tt_buffer_complete,
 };
 
 void xhci_init_driver(struct hc_driver *drv,

drivers/usb/host/xhci.h

···
 #define EP_GETTING_NO_STREAMS	(1 << 5)
 #define EP_HARD_CLEAR_TOGGLE	(1 << 6)
 #define EP_SOFT_CLEAR_TOGGLE	(1 << 7)
+/* usb_hub_clear_tt_buffer is in progress */
+#define EP_CLEARING_TT		(1 << 8)
 	/* ----  Related to URB cancellation ---- */
 	struct list_head	cancelled_td_list;
 	/* Watchdog timer for stop endpoint command to cancel URBs */
···
 
 void xhci_ring_ep_doorbell(struct xhci_hcd *xhci, unsigned int slot_id,
 		unsigned int ep_index, unsigned int stream_id);
+void xhci_ring_doorbell_for_active_rings(struct xhci_hcd *xhci,
+		unsigned int slot_id,
+		unsigned int ep_index);
 void xhci_cleanup_command_queue(struct xhci_hcd *xhci);
 void inc_deq(struct xhci_hcd *xhci, struct xhci_ring *ring);
 unsigned int count_trbs(u64 addr, u64 len);