[PATCH v29 02/33] xhci: add helper to stop endpoint and wait for completion

[Wesley Cheng <quic_wcheng@xxxxxxxxxxx>]

From: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>

Expose xhci_stop_endpoint_sync() which is a synchronous variant of
xhci_queue_stop_endpoint().  This is useful for client drivers that are
using the secondary interrupters, and need to stop the current endpoint
session.

This does not go through the normal xhci_handle_cmd_stop_ep() command
completion handler, because it utilizes the completion path to achieve
synchronous behavior.  Users of this API are primarily intended to be
clients that maintain their own transfer rings, such as in the case of USB
audio offload.

Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Signed-off-by: Wesley Cheng <quic_wcheng@xxxxxxxxxxx>
---
 drivers/usb/host/xhci.c | 45 +++++++++++++++++++++++++++++++++++++++++
 drivers/usb/host/xhci.h |  2 ++
 2 files changed, 47 insertions(+)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index ed1bb7ed44b0..8d7566e33faf 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -2784,6 +2784,51 @@ static int xhci_reserve_bandwidth(struct xhci_hcd *xhci,
 	return -ENOMEM;
 }
 
+/*
+ * Synchronous XHCI stop endpoint helper.  Issues the stop endpoint command and
+ * waits for the command completion before returning.  This does not call
+ * xhci_handle_cmd_stop_ep(), which has additional handling for 'context error'
+ * cases, along with transfer ring cleanup.
+ *
+ * xhci_stop_endpoint_sync() is intended to be utilized by clients that manage
+ * their own transfer ring, such as offload situations.
+ */
+int xhci_stop_endpoint_sync(struct xhci_hcd *xhci, struct xhci_virt_ep *ep, int suspend,
+			    gfp_t gfp_flags)
+{
+	struct xhci_command *command;
+	unsigned long flags;
+	int ret;
+
+	command = xhci_alloc_command(xhci, true, gfp_flags);
+	if (!command)
+		return -ENOMEM;
+
+	spin_lock_irqsave(&xhci->lock, flags);
+	ret = xhci_queue_stop_endpoint(xhci, command, ep->vdev->slot_id,
+				       ep->ep_index, suspend);
+	if (ret < 0) {
+		spin_unlock_irqrestore(&xhci->lock, flags);
+		goto out;
+	}
+
+	xhci_ring_cmd_db(xhci);
+	spin_unlock_irqrestore(&xhci->lock, flags);
+
+	wait_for_completion(command->completion);
+
+	/* No handling for COMP_CONTEXT_STATE_ERROR done at command completion*/
+	if (command->status == COMP_COMMAND_ABORTED ||
+	    command->status == COMP_COMMAND_RING_STOPPED) {
+		xhci_warn(xhci, "Timeout while waiting for stop endpoint command\n");
+		ret = -ETIME;
+	}
+out:
+	xhci_free_command(xhci, command);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xhci_stop_endpoint_sync);
 
 /* Issue a configure endpoint command or evaluate context command
  * and wait for it to finish.
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 324644165d93..51a992d8ffcf 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1917,6 +1917,8 @@ void xhci_ring_doorbell_for_active_rings(struct xhci_hcd *xhci,
 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);
+int xhci_stop_endpoint_sync(struct xhci_hcd *xhci, struct xhci_virt_ep *ep,
+			    int suspend, gfp_t gfp_flags);
 
 /* xHCI roothub code */
 void xhci_set_link_state(struct xhci_hcd *xhci, struct xhci_port *port,