usb: xhci: Add DbC support in xHCI driver

xHCI compatible USB host controllers(i.e. super-speed USB3 controllers)
can be implemented with the Debug Capability(DbC). It presents a debug
device which is fully compliant with the USB framework and provides the
equivalent of a very high performance full-duplex serial link. The debug
capability operation model and registers interface are defined in 7.6.8
of the xHCI specification, revision 1.1.

The DbC debug device shares a root port with the xHCI host. By default,
the debug capability is disabled and the root port is assigned to xHCI.
When the DbC is enabled, the root port will be assigned to the DbC debug
device, and the xHCI sees nothing on this port. This implementation uses
a sysfs node named <dbc> under the xHCI device to manage the enabling
and disabling of the debug capability.

When the debug capability is enabled, it will present a debug device
through the debug port. This debug device is fully compliant with the
USB3 framework, and it can be enumerated by a debug host on the other
end of the USB link. As soon as the debug device is configured, a TTY
serial device named /dev/ttyDBC0 will be created.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 497 insertions, 0 deletions

diff --git a/drivers/usb/host/xhci-dbgtty.c b/drivers/usb/host/xhci-dbgtty.c
new file mode 100644
index 000000000000..48811d72a94c
--- /dev/null
+++ b/drivers/usb/host/xhci-dbgtty.c
@@ -0,0 +1,497 @@
+/**
+ * xhci-dbgtty.c - tty glue for xHCI debug capability
+ *
+ * Copyright (C) 2017 Intel Corporation
+ *
+ * Author: Lu Baolu <baolu.lu@linux.intel.com>
+ */
+
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+
+#include "xhci.h"
+#include "xhci-dbgcap.h"
+
+static unsigned int
+dbc_send_packet(struct dbc_port *port, char *packet, unsigned int size)
+{
+	unsigned int		len;
+
+	len = kfifo_len(&port->write_fifo);
+	if (len < size)
+		size = len;
+	if (size != 0)
+		size = kfifo_out(&port->write_fifo, 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 = dbc_ep_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 = dbc_ep_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);
+	dbc_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 < DBC_QUEUE_SIZE; i++) {
+		req = dbc_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 = kfifo_in(&port->write_fifo, 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 = kfifo_put(&port->write_fifo, ch);
+	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 = kfifo_avail(&port->write_fifo);
+	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 = kfifo_len(&port->write_fifo);
+	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 = kfifo_alloc(&port->write_fifo, DBC_WRITE_BUF_SIZE, GFP_KERNEL);
+	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);
+	kfifo_free(&port->write_fifo);
+
+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;
+
+	kfifo_free(&port->write_fifo);
+	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);
+}