Re: [PATCH v3 2/3] usb: xhci: Add DbC support in xHCI driver

[Mathias Nyman]

Ok, review last part

> diff --git a/drivers/usb/host/xhci-dbgtty.c b/drivers/usb/host/xhci-dbgtty.c
> new file mode 100644
> index 0000000..fe5fef0
> --- /dev/null
> +++ b/drivers/usb/host/xhci-dbgtty.c
> @@ -0,0 +1,586 @@
> +/**
> + * xhci-dbgtty.c - tty glue for xHCI debug capability
> + *
> + * Copyright (C) 2017 Intel Corporation
> + *
> + * Author: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/slab.h>
> +#include <linux/tty.h>
> +#include <linux/tty_flip.h>
> +
> +#include "xhci.h"
> +#include "xhci-dbgcap.h"
> +
> +static int dbc_buf_alloc(struct dbc_buf *db, unsigned int size)
> +{
> +	db->buf_buf = kzalloc(size, GFP_KERNEL);
> +	if (!db->buf_buf)
> +		return -ENOMEM;
> +
> +	db->buf_size = size;
> +	db->buf_put = db->buf_buf;
> +	db->buf_get = db->buf_buf;
> +
> +	return 0;
> +}
> +
> +static void dbc_buf_free(struct dbc_buf *db)
> +{
> +	kfree(db->buf_buf);
> +	db->buf_buf = NULL;
> +}
> +
> +static unsigned int dbc_buf_data_avail(struct dbc_buf *db)
> +{
> +	return (db->buf_size + db->buf_put - db->buf_get) % db->buf_size;
> +}
> +
> +static unsigned int dbc_buf_space_avail(struct dbc_buf *db)
> +{
> +	return (db->buf_size + db->buf_get - db->buf_put - 1) % db->buf_size;
> +}
> +
> +static unsigned int
> +dbc_buf_put(struct dbc_buf *db, const char *buf, unsigned int count)
> +{
> +	unsigned int	len;
> +
> +	len  = dbc_buf_space_avail(db);

extra whitespace i think

> +	if (count > len)
> +		count = len;
> +
> +	if (count == 0)
> +		return 0;
> +
> +	len = db->buf_buf + db->buf_size - db->buf_put;
> +	if (count > len) {
> +		memcpy(db->buf_put, buf, len);
> +		memcpy(db->buf_buf, buf + len, count - len);
> +		db->buf_put = db->buf_buf + count - len;
> +	} else {
> +		memcpy(db->buf_put, buf, count);
> +		if (count < len)
> +			db->buf_put += count;
> +		else
> +			db->buf_put = db->buf_buf;
> +	}
> +
> +	return count;
> +}
> +
> +static unsigned int
> +dbc_buf_get(struct dbc_buf *db, char *buf, unsigned int count)
> +{
> +	unsigned int	len;
> +
> +	len = dbc_buf_data_avail(db);
> +	if (count > len)
> +		count = len;
> +
> +	if (count == 0)
> +		return 0;
> +
> +	len = db->buf_buf + db->buf_size - db->buf_get;
> +	if (count > len) {
> +		memcpy(buf, db->buf_get, len);
> +		memcpy(buf + len, db->buf_buf, count - len);
> +		db->buf_get = db->buf_buf + count - len;
> +	} else {
> +		memcpy(buf, db->buf_get, count);
> +		if (count < len)
> +			db->buf_get += count;
> +		else
> +			db->buf_get = db->buf_buf;
> +	}
> +
> +	return count;
> +}
> +
> +static unsigned int
> +dbc_send_packet(struct dbc_port *port, char *packet, unsigned int size)
> +{
> +	unsigned int		len;
> +
> +	len = dbc_buf_data_avail(&port->port_write_buf);
> +	if (len < size)
> +		size = len;
> +	if (size != 0)
> +		size = dbc_buf_get(&port->port_write_buf, packet, size);
> +	return size;
> +}
> +
> +static int dbc_start_tx(struct dbc_port *port)
> +	__releases(&port->port_lock)
> +	__acquires(&port->port_lock)
> +{
> +	int			len;
> +	struct dbc_request	*req;
> +	int			status = 0;
> +	bool			do_tty_wake = false;
> +	struct list_head	*pool = &port->write_pool;
> +
> +	while (!list_empty(pool)) {
> +		req = list_entry(pool->next, struct dbc_request, list_pool);
> +		len = dbc_send_packet(port, req->buf, DBC_MAX_PACKET);
> +		if (len == 0)
> +			break;
> +		do_tty_wake = true;
> +
> +		req->length = len;
> +		list_del(&req->list_pool);
> +
> +		spin_unlock(&port->port_lock);
> +		status = port->out->queue(port->out, req, GFP_ATOMIC);
> +		spin_lock(&port->port_lock);
> +
> +		if (status) {
> +			list_add(&req->list_pool, pool);
> +			break;
> +		}
> +	}
> +
> +	if (do_tty_wake && port->port.tty)
> +		tty_wakeup(port->port.tty);
> +
> +	return status;
> +}
> +
> +static void dbc_start_rx(struct dbc_port *port)
> +	__releases(&port->port_lock)
> +	__acquires(&port->port_lock)
> +{
> +	struct dbc_request	*req;
> +	int			status;
> +	struct list_head	*pool = &port->read_pool;
> +
> +	while (!list_empty(pool)) {
> +		if (!port->port.tty)
> +			break;
> +
> +		req = list_entry(pool->next, struct dbc_request, list_pool);
> +		list_del(&req->list_pool);
> +		req->length = DBC_MAX_PACKET;
> +
> +		spin_unlock(&port->port_lock);
> +		status = port->in->queue(port->in, req, GFP_ATOMIC);
> +		spin_lock(&port->port_lock);
> +
> +		if (status) {
> +			list_add(&req->list_pool, pool);
> +			break;
> +		}
> +	}
> +}
> +
> +static void
> +dbc_read_complete(struct xhci_hcd *xhci, struct dbc_request *req)
> +{
> +	struct xhci_dbc		*dbc = xhci->dbc;
> +	struct dbc_port		*port = &dbc->port;
> +
> +	spin_lock(&port->port_lock);
> +	list_add_tail(&req->list_pool, &port->read_queue);
> +	tasklet_schedule(&port->push);
> +	spin_unlock(&port->port_lock);
> +}
> +
> +static void dbc_write_complete(struct xhci_hcd *xhci, struct dbc_request *req)
> +{
> +	struct xhci_dbc		*dbc = xhci->dbc;
> +	struct dbc_port		*port = &dbc->port;
> +
> +	spin_lock(&port->port_lock);
> +	list_add(&req->list_pool, &port->write_pool);
> +	switch (req->status) {
> +	case 0:
> +		dbc_start_tx(port);
> +		break;
> +	case -ESHUTDOWN:
> +		break;
> +	default:
> +		xhci_warn(xhci, "unexpected write complete status %d\n",
> +			  req->status);
> +		break;
> +	}
> +	spin_unlock(&port->port_lock);
> +}
> +
> +void xhci_dbc_free_req(struct dbc_ep *dep, struct dbc_request *req)
> +{
> +	kfree(req->buf);
> +	dep->free_request(dep, req);
> +}
> +
> +static int
> +xhci_dbc_alloc_requests(struct dbc_ep *dep, struct list_head *head,
> +			void (*fn)(struct xhci_hcd *, struct dbc_request *))
> +{
> +	int			i;
> +	struct dbc_request	*req;
> +
> +	for (i = 0; i < QUEUE_SIZE; i++) {
> +		req = dep->alloc_request(dep, GFP_ATOMIC);
> +		if (!req)
> +			break;
> +
> +		req->length = DBC_MAX_PACKET;
> +		req->buf = kmalloc(req->length, GFP_KERNEL);
> +		if (!req->buf) {
> +			xhci_dbc_free_req(dep, req);
> +			break;
> +		}
> +
> +		req->complete = fn;
> +		list_add_tail(&req->list_pool, head);
> +	}
> +
> +	return list_empty(head) ? -ENOMEM : 0;
> +}
> +
> +static void
> +xhci_dbc_free_requests(struct dbc_ep *dep, struct list_head *head)
> +{
> +	struct dbc_request	*req;
> +
> +	while (!list_empty(head)) {
> +		req = list_entry(head->next, struct dbc_request, list_pool);
> +		list_del(&req->list_pool);
> +		xhci_dbc_free_req(dep, req);
> +	}
> +}
> +
> +static int dbc_tty_install(struct tty_driver *driver, struct tty_struct *tty)
> +{
> +	struct dbc_port		*port = driver->driver_state;
> +
> +	tty->driver_data = port;
> +
> +	return tty_port_install(&port->port, driver, tty);
> +}
> +
> +static int dbc_tty_open(struct tty_struct *tty, struct file *file)
> +{
> +	struct dbc_port		*port = tty->driver_data;
> +
> +	return tty_port_open(&port->port, tty, file);
> +}
> +
> +static void dbc_tty_close(struct tty_struct *tty, struct file *file)
> +{
> +	struct dbc_port		*port = tty->driver_data;
> +
> +	tty_port_close(&port->port, tty, file);
> +}
> +
> +static int dbc_tty_write(struct tty_struct *tty,
> +			 const unsigned char *buf,
> +			 int count)
> +{
> +	struct dbc_port		*port = tty->driver_data;
> +	unsigned long		flags;
> +
> +	spin_lock_irqsave(&port->port_lock, flags);
> +	if (count)
> +		count = dbc_buf_put(&port->port_write_buf, buf, count);
> +	dbc_start_tx(port);
> +	spin_unlock_irqrestore(&port->port_lock, flags);
> +
> +	return count;
> +}
> +
> +static int dbc_tty_put_char(struct tty_struct *tty, unsigned char ch)
> +{
> +	struct dbc_port		*port = tty->driver_data;
> +	unsigned long		flags;
> +	int			status;
> +
> +	spin_lock_irqsave(&port->port_lock, flags);
> +	status = dbc_buf_put(&port->port_write_buf, &ch, 1);
> +	spin_unlock_irqrestore(&port->port_lock, flags);
> +
> +	return status;
> +}
> +
> +static void dbc_tty_flush_chars(struct tty_struct *tty)
> +{
> +	struct dbc_port		*port = tty->driver_data;
> +	unsigned long		flags;
> +
> +	spin_lock_irqsave(&port->port_lock, flags);
> +	dbc_start_tx(port);
> +	spin_unlock_irqrestore(&port->port_lock, flags);
> +}
> +
> +static int dbc_tty_write_room(struct tty_struct *tty)
> +{
> +	struct dbc_port		*port = tty->driver_data;
> +	unsigned long		flags;
> +	int			room = 0;
> +
> +	spin_lock_irqsave(&port->port_lock, flags);
> +	room = dbc_buf_space_avail(&port->port_write_buf);
> +	spin_unlock_irqrestore(&port->port_lock, flags);
> +
> +	return room;
> +}
> +
> +static int dbc_tty_chars_in_buffer(struct tty_struct *tty)
> +{
> +	struct dbc_port		*port = tty->driver_data;
> +	unsigned long		flags;
> +	int			chars = 0;
> +
> +	spin_lock_irqsave(&port->port_lock, flags);
> +	chars = dbc_buf_data_avail(&port->port_write_buf);
> +	spin_unlock_irqrestore(&port->port_lock, flags);
> +
> +	return chars;
> +}
> +
> +static void dbc_tty_unthrottle(struct tty_struct *tty)
> +{
> +	struct dbc_port		*port = tty->driver_data;
> +	unsigned long		flags;
> +
> +	spin_lock_irqsave(&port->port_lock, flags);
> +	tasklet_schedule(&port->push);
> +	spin_unlock_irqrestore(&port->port_lock, flags);
> +}
> +
> +static const struct tty_operations dbc_tty_ops = {
> +	.install		= dbc_tty_install,
> +	.open			= dbc_tty_open,
> +	.close			= dbc_tty_close,
> +	.write			= dbc_tty_write,
> +	.put_char		= dbc_tty_put_char,
> +	.flush_chars		= dbc_tty_flush_chars,
> +	.write_room		= dbc_tty_write_room,
> +	.chars_in_buffer	= dbc_tty_chars_in_buffer,
> +	.unthrottle		= dbc_tty_unthrottle,
> +};
> +
> +static struct tty_driver *dbc_tty_driver;
> +
> +int xhci_dbc_tty_register_driver(struct xhci_hcd *xhci)
> +{
> +	int			status;
> +	struct xhci_dbc		*dbc = xhci->dbc;
> +
> +	dbc_tty_driver = tty_alloc_driver(1, TTY_DRIVER_REAL_RAW |
> +					  TTY_DRIVER_DYNAMIC_DEV);
> +	if (IS_ERR(dbc_tty_driver)) {
> +		status = PTR_ERR(dbc_tty_driver);
> +		dbc_tty_driver = NULL;
> +		return status;
> +	}
> +
> +	dbc_tty_driver->driver_name = "dbc_serial";
> +	dbc_tty_driver->name = "ttyDBC";
> +
> +	dbc_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
> +	dbc_tty_driver->subtype = SERIAL_TYPE_NORMAL;
> +	dbc_tty_driver->init_termios = tty_std_termios;
> +	dbc_tty_driver->init_termios.c_cflag =
> +			B9600 | CS8 | CREAD | HUPCL | CLOCAL;
> +	dbc_tty_driver->init_termios.c_ispeed = 9600;
> +	dbc_tty_driver->init_termios.c_ospeed = 9600;
> +	dbc_tty_driver->driver_state = &dbc->port;
> +
> +	tty_set_operations(dbc_tty_driver, &dbc_tty_ops);
> +
> +	status = tty_register_driver(dbc_tty_driver);
> +	if (status) {
> +		xhci_err(xhci,
> +			 "can't register dbc tty driver, err %d\n", status);
> +		put_tty_driver(dbc_tty_driver);
> +		dbc_tty_driver = NULL;
> +	}
> +
> +	return status;
> +}
> +
> +void xhci_dbc_tty_unregister_driver(void)
> +{
> +	tty_unregister_driver(dbc_tty_driver);
> +	put_tty_driver(dbc_tty_driver);
> +	dbc_tty_driver = NULL;
> +}
> +
> +static void dbc_rx_push(unsigned long _port)
> +{
> +	struct dbc_request	*req;
> +	struct tty_struct	*tty;
> +	bool			do_push = false;
> +	bool			disconnect = false;
> +	struct dbc_port		*port = (void *)_port;
> +	struct list_head	*queue = &port->read_queue;
> +
> +	spin_lock_irq(&port->port_lock);
> +	tty = port->port.tty;
> +	while (!list_empty(queue)) {
> +		req = list_first_entry(queue, struct dbc_request, list_pool);
> +
> +		if (tty && tty_throttled(tty))
> +			break;
> +
> +		switch (req->status) {
> +		case 0:
> +			break;
> +		case -ESHUTDOWN:
> +			disconnect = true;
> +			break;
> +		default:
> +			pr_warn("ttyDBC0: unexpected RX status %d\n",
> +				req->status);
> +			break;
> +		}
> +
> +		if (req->actual) {
> +			char		*packet = req->buf;
> +			unsigned int	n, size = req->actual;
> +			int		count;
> +
> +			n = port->n_read;
> +			if (n) {
> +				packet += n;
> +				size -= n;
> +			}
> +
> +			count = tty_insert_flip_string(&port->port, packet,
> +						       size);
> +			if (count)
> +				do_push = true;
> +			if (count != size) {
> +				port->n_read += count;
> +				break;
> +			}
> +			port->n_read = 0;
> +		}
> +
> +		list_move(&req->list_pool, &port->read_pool);
> +	}
> +
> +	if (do_push)
> +		tty_flip_buffer_push(&port->port);
> +
> +	if (!list_empty(queue) && tty) {
> +		if (!tty_throttled(tty)) {
> +			if (do_push)
> +				tasklet_schedule(&port->push);
> +			else
> +				pr_warn("ttyDBC0: RX not scheduled?\n");
> +		}
> +	}
> +
> +	if (!disconnect)
> +		dbc_start_rx(port);
> +
> +	spin_unlock_irq(&port->port_lock);
> +}
> +
> +static int dbc_port_activate(struct tty_port *_port, struct tty_struct *tty)
> +{
> +	struct dbc_port	*port = container_of(_port, struct dbc_port, port);
> +
> +	spin_lock_irq(&port->port_lock);
> +	dbc_start_rx(port);
> +	spin_unlock_irq(&port->port_lock);
> +
> +	return 0;
> +}
> +
> +static const struct tty_port_operations dbc_port_ops = {
> +	.activate =	dbc_port_activate,
> +};
> +
> +static void
> +xhci_dbc_tty_init_port(struct xhci_hcd *xhci, struct dbc_port *port)
> +{
> +	tty_port_init(&port->port);
> +	spin_lock_init(&port->port_lock);
> +	tasklet_init(&port->push, dbc_rx_push, (unsigned long)port);
> +	INIT_LIST_HEAD(&port->read_pool);
> +	INIT_LIST_HEAD(&port->read_queue);
> +	INIT_LIST_HEAD(&port->write_pool);
> +
> +	port->in =		get_in_ep(xhci);
> +	port->out =		get_out_ep(xhci);
> +	port->port.ops =	&dbc_port_ops;
> +	port->n_read =		0;
> +}
> +
> +static void
> +xhci_dbc_tty_exit_port(struct dbc_port *port)
> +{
> +	tasklet_kill(&port->push);
> +	tty_port_destroy(&port->port);
> +}
> +
> +int xhci_dbc_tty_register_device(struct xhci_hcd *xhci)
> +{
> +	int			ret;
> +	struct device		*tty_dev;
> +	struct xhci_dbc		*dbc = xhci->dbc;
> +	struct dbc_port		*port = &dbc->port;
> +
> +	xhci_dbc_tty_init_port(xhci, port);
> +	tty_dev = tty_port_register_device(&port->port,
> +					   dbc_tty_driver, 0, NULL);
> +	ret = IS_ERR_OR_NULL(tty_dev);
> +	if (ret)
> +		goto register_fail;
> +
> +	ret = dbc_buf_alloc(&port->port_write_buf, WRITE_BUF_SIZE);
> +	if (ret)
> +		goto buf_alloc_fail;
> +
> +	ret = xhci_dbc_alloc_requests(port->in, &port->read_pool,
> +				      dbc_read_complete);
> +	if (ret)
> +		goto request_fail;
> +
> +	ret = xhci_dbc_alloc_requests(port->out, &port->write_pool,
> +				      dbc_write_complete);
> +	if (ret)
> +		goto request_fail;
> +
> +	port->registered = true;
> +
> +	return 0;
> +
> +request_fail:
> +	xhci_dbc_free_requests(port->in, &port->read_pool);
> +	xhci_dbc_free_requests(port->out, &port->write_pool);
> +	dbc_buf_free(&port->port_write_buf);
> +
> +buf_alloc_fail:
> +	tty_unregister_device(dbc_tty_driver, 0);
> +
> +register_fail:
> +	xhci_dbc_tty_exit_port(port);
> +
> +	xhci_err(xhci, "can't register tty port, err %d\n", ret);
> +
> +	return ret;
> +}
> +
> +void xhci_dbc_tty_unregister_device(struct xhci_hcd *xhci)
> +{
> +	struct xhci_dbc		*dbc = xhci->dbc;
> +	struct dbc_port		*port = &dbc->port;
> +
> +	tty_unregister_device(dbc_tty_driver, 0);
> +	xhci_dbc_tty_exit_port(port);
> +	port->registered = false;
> +
> +	dbc_buf_free(&port->port_write_buf);
> +	xhci_dbc_free_requests(get_out_ep(xhci), &port->read_pool);
> +	xhci_dbc_free_requests(get_out_ep(xhci), &port->read_queue);
> +	xhci_dbc_free_requests(get_in_ep(xhci), &port->write_pool);
> +}
> diff --git a/drivers/usb/host/xhci-trace.h b/drivers/usb/host/xhci-trace.h
> index 8ce96de..bf2013c 100644
> --- a/drivers/usb/host/xhci-trace.h
> +++ b/drivers/usb/host/xhci-trace.h
> @@ -26,6 +26,7 @@
>   
>   #include <linux/tracepoint.h>
>   #include "xhci.h"
> +#include "xhci-dbgcap.h"
>   
>   #define XHCI_MSG_MAX	500
>   
> @@ -158,6 +159,21 @@ DEFINE_EVENT(xhci_log_trb, xhci_queue_trb,
>   	TP_ARGS(ring, trb)
>   );
>   
> +DEFINE_EVENT(xhci_log_trb, xhci_dbc_handle_event,
> +	TP_PROTO(struct xhci_ring *ring, struct xhci_generic_trb *trb),
> +	TP_ARGS(ring, trb)
> +);
> +
> +DEFINE_EVENT(xhci_log_trb, xhci_dbc_handle_transfer,
> +	TP_PROTO(struct xhci_ring *ring, struct xhci_generic_trb *trb),
> +	TP_ARGS(ring, trb)
> +);
> +
> +DEFINE_EVENT(xhci_log_trb, xhci_dbc_gadget_ep_queue,
> +	TP_PROTO(struct xhci_ring *ring, struct xhci_generic_trb *trb),
> +	TP_ARGS(ring, trb)
> +);
> +
>   DECLARE_EVENT_CLASS(xhci_log_virt_dev,
>   	TP_PROTO(struct xhci_virt_device *vdev),
>   	TP_ARGS(vdev),
> @@ -453,6 +469,50 @@ DEFINE_EVENT(xhci_log_ring, xhci_inc_deq,
>   	TP_PROTO(struct xhci_ring *ring),
>   	TP_ARGS(ring)
>   );
> +
> +DECLARE_EVENT_CLASS(xhci_dbc_log_request,
> +	TP_PROTO(struct dbc_request *req),
> +	TP_ARGS(req),
> +	TP_STRUCT__entry(
> +		__field(struct dbc_request *, req)
> +		__field(bool, dir)
> +		__field(unsigned int, actual)
> +		__field(unsigned int, length)
> +		__field(int, status)
> +	),
> +	TP_fast_assign(
> +		__entry->req = req;
> +		__entry->dir = req->direction;
> +		__entry->actual = req->actual;
> +		__entry->length = req->length;
> +		__entry->status = req->status;
> +	),
> +	TP_printk("%s: req %p length %u/%u ==> %d",
> +		__entry->dir ? "bulk-in" : "bulk-out",
> +		__entry->req, __entry->actual,
> +		__entry->length, __entry->status
> +	)
> +);
> +
> +DEFINE_EVENT(xhci_dbc_log_request, xhci_dbc_alloc_request,
> +	TP_PROTO(struct dbc_request *req),
> +	TP_ARGS(req)
> +);
> +
> +DEFINE_EVENT(xhci_dbc_log_request, xhci_dbc_free_request,
> +	TP_PROTO(struct dbc_request *req),
> +	TP_ARGS(req)
> +);
> +
> +DEFINE_EVENT(xhci_dbc_log_request, xhci_dbc_queue_request,
> +	TP_PROTO(struct dbc_request *req),
> +	TP_ARGS(req)
> +);
> +
> +DEFINE_EVENT(xhci_dbc_log_request, xhci_dbc_giveback_request,
> +	TP_PROTO(struct dbc_request *req),
> +	TP_ARGS(req)
> +);
>   #endif /* __XHCI_TRACE_H */
>   
>   /* this part must be outside header guard */
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index b2ff1ff..39a9a88 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -32,6 +32,7 @@
>   #include "xhci.h"
>   #include "xhci-trace.h"
>   #include "xhci-mtk.h"
> +#include "xhci-dbgcap.h"
>   
>   #define DRIVER_AUTHOR "Sarah Sharp"
>   #define DRIVER_DESC "'eXtensible' Host Controller (xHC) Driver"
> @@ -632,6 +633,9 @@ int xhci_run(struct usb_hcd *hcd)
>   	}
>   	xhci_dbg_trace(xhci, trace_xhci_dbg_init,
>   			"Finished xhci_run for USB2 roothub");
> +
> +	dbc_create_sysfs_file(xhci);
> +
>   	return 0;
>   }
>   EXPORT_SYMBOL_GPL(xhci_run);
> @@ -660,6 +664,8 @@ static void xhci_stop(struct usb_hcd *hcd)
>   		return;
>   	}
>   
> +	dbc_remove_sysfs_file(xhci);
> +
>   	spin_lock_irq(&xhci->lock);
>   	xhci->xhc_state |= XHCI_STATE_HALTED;
>   	xhci->cmd_ring_state = CMD_RING_STATE_STOPPED;
> @@ -876,6 +882,8 @@ int xhci_suspend(struct xhci_hcd *xhci, bool do_wakeup)
>   			xhci->shared_hcd->state != HC_STATE_SUSPENDED)
>   		return -EINVAL;
>   
> +	xhci_dbc_suspend(xhci);
> +
>   	/* Clear root port wake on bits if wakeup not allowed. */
>   	if (!do_wakeup)
>   		xhci_disable_port_wake_on_bits(xhci);
> @@ -1071,6 +1079,8 @@ int xhci_resume(struct xhci_hcd *xhci, bool hibernated)
>   
>   	spin_unlock_irq(&xhci->lock);
>   
> +	xhci_dbc_resume(xhci);
> +
>    done:
>   	if (retval == 0) {
>   		/* Resume root hubs only when have pending events. */
> diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
> index 62bcdcd..bae2538 100644
> --- a/drivers/usb/host/xhci.h
> +++ b/drivers/usb/host/xhci.h
> @@ -1850,6 +1850,7 @@ struct xhci_hcd {
>   /* Compliance Mode Timer Triggered every 2 seconds */
>   #define COMP_MODE_RCVRY_MSECS 2000
>   
> +	void			*dbc;
>   	/* platform-specific data -- must come last */
>   	unsigned long		priv[0] __aligned(sizeof(s64));
>   };

Did only a really quick overview of this, It all looks fine.
If you make a new revision I'll send it out after rc1

Thanks
-Mathias