---
 drivers/usb/host/xhci-sideband.c  | 29 ++++++++++++++++++++++++++++-
 drivers/usb/host/xhci.c           |  3 +++
 include/linux/usb/xhci-sideband.h | 30 +++++++++++++++++++++++++++++-
 3 files changed, 60 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/host/xhci-sideband.c b/drivers/usb/host/xhci-sideband.c
index 742bbc6c2d9b..d49f9886dd84 100644
--- a/drivers/usb/host/xhci-sideband.c
+++ b/drivers/usb/host/xhci-sideband.c

@@ -88,6 +88,30 @@ __xhci_sideband_remove_endpoint(struct xhci_sideband *sb, struct xhci_virt_ep *e

 /* sideband api functions */

+/**
+ * xhci_sideband_notify_ep_ring_free - notify client of xfer ring free
+ * @sb: sideband instance for this usb device
+ * @ep_index: usb endpoint index
+ *
+ * Notifies the xHCI sideband client driver of a xHCI transfer ring free
+ * routine.  This will allow for the client to ensure that all transfers
+ * are completed.
+ *
+ * The callback should be synchronous, as the ring free happens after.
+ */
+void xhci_sideband_notify_ep_ring_free(struct xhci_sideband *sb,
+                                      unsigned int ep_index)
+{
+       struct xhci_sideband_event evt;
+
+       evt.type = XHCI_SIDEBAND_XFER_RING_FREE;
+       evt.evt_data = &ep_index;
+
+       if (sb->notify_client)
+               sb->notify_client(sb->intf, &evt);
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_notify_ep_ring_free);
+
 /**
  * xhci_sideband_add_endpoint - add endpoint to sideband access list
  * @sb: sideband instance for this usb device

@@ -342,7 +366,9 @@ EXPORT_SYMBOL_GPL(xhci_sideband_interrupter_id);
  * Return: pointer to a new xhci_sideband instance if successful. NULL otherwise.
  */
 struct xhci_sideband *
-xhci_sideband_register(struct usb_interface *intf, enum xhci_sideband_type type)
+xhci_sideband_register(struct usb_interface *intf, enum xhci_sideband_type type,
+                      int (*notify_client)(struct usb_interface *intf,
+                                   struct xhci_sideband_event *evt))
 {
        struct usb_device *udev = interface_to_usbdev(intf);
        struct usb_hcd *hcd = bus_to_hcd(udev->bus);

@@ -381,6 +407,7 @@ xhci_sideband_register(struct usb_interface *intf, enum xhci_sideband_type type)
        sb->vdev = vdev;
        sb->intf = intf;
        sb->type = type;
+       sb->notify_client = notify_client;
        vdev->sideband = sb;

        spin_unlock_irq(&xhci->lock);

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 61950a350432..91e2d6eac8b7 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c

@@ -20,6 +20,7 @@
 #include <linux/string_choices.h>
 #include <linux/dmi.h>
 #include <linux/dma-mapping.h>
+#include <linux/usb/xhci-sideband.h>

 #include "xhci.h"
 #include "xhci-trace.h"

@@ -3919,6 +3920,8 @@ static int xhci_discover_or_reset_device(struct usb_hcd *hcd,
                }

                if (ep->ring) {
+                       if (ep->sideband)
+                               xhci_sideband_notify_ep_ring_free(ep->sideband, i);
                        xhci_debugfs_remove_endpoint(xhci, virt_dev, i);
                        xhci_free_endpoint_ring(xhci, virt_dev, i);
                }

diff --git a/include/linux/usb/xhci-sideband.h b/include/linux/usb/xhci-sideband.h
index f8722afb8a2d..45288c392f6e 100644
--- a/include/linux/usb/xhci-sideband.h
+++ b/include/linux/usb/xhci-sideband.h

@@ -21,6 +21,20 @@ enum xhci_sideband_type {
        XHCI_SIDEBAND_VENDOR,
 };

+enum xhci_sideband_notify_type {
+       XHCI_SIDEBAND_XFER_RING_FREE,
+};
+
+/**
+ * struct xhci_sideband_event - sideband event
+ * @type: notifier type
+ * @evt_data: event data
+ */
+struct xhci_sideband_event {
+       enum xhci_sideband_notify_type type;
+       void *evt_data;
+};
+
 /**
  * struct xhci_sideband - representation of a sideband accessed usb device.
  * @xhci: The xhci host controller the usb device is connected to

@@ -30,6 +44,7 @@ enum xhci_sideband_type {
  * @type: xHCI sideband type
  * @mutex: mutex for sideband operations
  * @intf: USB sideband client interface
+ * @notify_client: callback for xHCI sideband sequences
  *
  * FIXME usb device accessed via sideband Keeping track of sideband accessed usb devices.
  */

@@ -44,10 +59,14 @@ struct xhci_sideband {
        struct mutex                    mutex;

        struct usb_interface            *intf;
+       int (*notify_client)(struct usb_interface *intf,
+                            struct xhci_sideband_event *evt);
 };

 struct xhci_sideband *
-xhci_sideband_register(struct usb_interface *intf, enum xhci_sideband_type type);
+xhci_sideband_register(struct usb_interface *intf, enum xhci_sideband_type type,
+                      int (*notify_client)(struct usb_interface *intf,
+                                   struct xhci_sideband_event *evt));
 void
 xhci_sideband_unregister(struct xhci_sideband *sb);
 int

@@ -71,4 +90,13 @@ void
 xhci_sideband_remove_interrupter(struct xhci_sideband *sb);
 int
 xhci_sideband_interrupter_id(struct xhci_sideband *sb);
+
+#if IS_ENABLED(CONFIG_USB_XHCI_SIDEBAND)
+void xhci_sideband_notify_ep_ring_free(struct xhci_sideband *sb,
+                                      unsigned int ep_index);
+#else
+static inline void xhci_sideband_notify_ep_ring_free(struct xhci_sideband *sb,
+                                                    unsigned int ep_index)
+{ }
+#endif /* IS_ENABLED(CONFIG_USB_XHCI_SIDEBAND) */
 #endif /* __LINUX_XHCI_SIDEBAND_H */