提交 715b1dc0 编写于 作者: J Jason Wessel 提交者: Greg Kroah-Hartman

USB: usb_debug, usb_generic_serial: implement multi urb write

The usb_debug driver, when used as the console, will always fail to
insert the carriage return and new line sequence as well as randomly
drop console output.  This is a result of only having the single
write_urb and that the tty layer will have a lock that prevents the
processing of the back to back urb requests.

The solution is to allow more than one urb to be outstanding and have
a slightly deeper transmit queue.  The idea and some code is borrowed
from the ftdi_sio usb driver.

The generic usb serial driver was modified so as to allow the classic
method of 1 write urb, or a multi write urb scheme with N allowed
outstanding urbs where N is controlled by max_in_flight_urbs.  When
max_in_flight_urbs in a "struct usb_serial_driver" is non zero the
multi write urb scheme will be used.

The size of 4000 was selected for the usb_debug driver so that the
driver lowers possibility of losing the queued console messages during
the kernel startup.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>
上级 b0cda8c5
......@@ -190,6 +190,88 @@ void usb_serial_generic_close(struct usb_serial_port *port)
generic_cleanup(port);
}
static int usb_serial_multi_urb_write(struct tty_struct *tty,
struct usb_serial_port *port, const unsigned char *buf, int count)
{
unsigned long flags;
struct urb *urb;
unsigned char *buffer;
int status;
int towrite;
int bwrite = 0;
dbg("%s - port %d", __func__, port->number);
if (count == 0)
dbg("%s - write request of 0 bytes", __func__);
while (count > 0) {
towrite = (count > port->bulk_out_size) ?
port->bulk_out_size : count;
spin_lock_irqsave(&port->lock, flags);
if (port->urbs_in_flight >
port->serial->type->max_in_flight_urbs) {
spin_unlock_irqrestore(&port->lock, flags);
dbg("%s - write limit hit\n", __func__);
return bwrite;
}
port->tx_bytes_flight += towrite;
port->urbs_in_flight++;
spin_unlock_irqrestore(&port->lock, flags);
buffer = kmalloc(towrite, GFP_ATOMIC);
if (!buffer) {
dev_err(&port->dev,
"%s ran out of kernel memory for urb ...\n", __func__);
goto error_no_buffer;
}
urb = usb_alloc_urb(0, GFP_ATOMIC);
if (!urb) {
dev_err(&port->dev, "%s - no more free urbs\n",
__func__);
goto error_no_urb;
}
/* Copy data */
memcpy(buffer, buf + bwrite, towrite);
usb_serial_debug_data(debug, &port->dev, __func__,
towrite, buffer);
/* fill the buffer and send it */
usb_fill_bulk_urb(urb, port->serial->dev,
usb_sndbulkpipe(port->serial->dev,
port->bulk_out_endpointAddress),
buffer, towrite,
usb_serial_generic_write_bulk_callback, port);
status = usb_submit_urb(urb, GFP_ATOMIC);
if (status) {
dev_err(&port->dev,
"%s - failed submitting write urb, error %d\n",
__func__, status);
goto error;
}
/* This urb is the responsibility of the host driver now */
usb_free_urb(urb);
dbg("%s write: %d", __func__, towrite);
count -= towrite;
bwrite += towrite;
}
return bwrite;
error:
usb_free_urb(urb);
error_no_urb:
kfree(buffer);
error_no_buffer:
spin_lock_irqsave(&port->lock, flags);
port->urbs_in_flight--;
port->tx_bytes_flight -= towrite;
spin_unlock_irqrestore(&port->lock, flags);
return bwrite;
}
int usb_serial_generic_write(struct tty_struct *tty,
struct usb_serial_port *port, const unsigned char *buf, int count)
{
......@@ -207,6 +289,11 @@ int usb_serial_generic_write(struct tty_struct *tty,
/* only do something if we have a bulk out endpoint */
if (serial->num_bulk_out) {
unsigned long flags;
if (serial->type->max_in_flight_urbs)
return usb_serial_multi_urb_write(tty, port,
buf, count);
spin_lock_irqsave(&port->lock, flags);
if (port->write_urb_busy) {
spin_unlock_irqrestore(&port->lock, flags);
......@@ -257,15 +344,18 @@ int usb_serial_generic_write_room(struct tty_struct *tty)
{
struct usb_serial_port *port = tty->driver_data;
struct usb_serial *serial = port->serial;
unsigned long flags;
int room = 0;
dbg("%s - port %d", __func__, port->number);
/* FIXME: Locking */
if (serial->num_bulk_out) {
if (!(port->write_urb_busy))
spin_lock_irqsave(&port->lock, flags);
if (serial->type->max_in_flight_urbs) {
if (port->urbs_in_flight < serial->type->max_in_flight_urbs)
room = port->bulk_out_size;
} else if (serial->num_bulk_out && !(port->write_urb_busy)) {
room = port->bulk_out_size;
}
spin_unlock_irqrestore(&port->lock, flags);
dbg("%s - returns %d", __func__, room);
return room;
......@@ -276,11 +366,16 @@ int usb_serial_generic_chars_in_buffer(struct tty_struct *tty)
struct usb_serial_port *port = tty->driver_data;
struct usb_serial *serial = port->serial;
int chars = 0;
unsigned long flags;
dbg("%s - port %d", __func__, port->number);
/* FIXME: Locking */
if (serial->num_bulk_out) {
if (serial->type->max_in_flight_urbs) {
spin_lock_irqsave(&port->lock, flags);
chars = port->tx_bytes_flight;
spin_unlock_irqrestore(&port->lock, flags);
} else if (serial->num_bulk_out) {
/* FIXME: Locking */
if (port->write_urb_busy)
chars = port->write_urb->transfer_buffer_length;
}
......@@ -363,12 +458,24 @@ EXPORT_SYMBOL_GPL(usb_serial_generic_read_bulk_callback);
void usb_serial_generic_write_bulk_callback(struct urb *urb)
{
unsigned long flags;
struct usb_serial_port *port = urb->context;
int status = urb->status;
dbg("%s - port %d", __func__, port->number);
port->write_urb_busy = 0;
if (port->serial->type->max_in_flight_urbs) {
spin_lock_irqsave(&port->lock, flags);
--port->urbs_in_flight;
port->tx_bytes_flight -= urb->transfer_buffer_length;
if (port->urbs_in_flight < 0)
port->urbs_in_flight = 0;
spin_unlock_irqrestore(&port->lock, flags);
} else {
/* Handle the case for single urb mode */
port->write_urb_busy = 0;
}
if (status) {
dbg("%s - nonzero write bulk status received: %d",
__func__, status);
......
......@@ -15,6 +15,7 @@
#include <linux/usb.h>
#include <linux/usb/serial.h>
#define URB_DEBUG_MAX_IN_FLIGHT_URBS 4000
#define USB_DEBUG_MAX_PACKET_SIZE 8
static struct usb_device_id id_table [] = {
......@@ -46,6 +47,7 @@ static struct usb_serial_driver debug_device = {
.id_table = id_table,
.num_ports = 1,
.open = usb_debug_open,
.max_in_flight_urbs = URB_DEBUG_MAX_IN_FLIGHT_URBS,
};
static int __init debug_init(void)
......
......@@ -91,6 +91,9 @@ struct usb_serial_port {
int write_urb_busy;
__u8 bulk_out_endpointAddress;
int tx_bytes_flight;
int urbs_in_flight;
wait_queue_head_t write_wait;
struct work_struct work;
char throttled;
......@@ -207,6 +210,7 @@ struct usb_serial_driver {
struct device_driver driver;
struct usb_driver *usb_driver;
struct usb_dynids dynids;
int max_in_flight_urbs;
int (*probe)(struct usb_serial *serial, const struct usb_device_id *id);
int (*attach)(struct usb_serial *serial);
......
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