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USB: serial: remove multi-urb write from generic driver
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Remove multi-urb write from the generic driver and simplify the
prepare_write_buffer prototype:

	int (*prepare_write_buffer)(struct usb_serial_port *port,
						void *dest, size_t size);

The default implementation simply fills dest with data from port write
fifo but drivers can override it if they need to process the outgoing
data (e.g. add headers).

Turn ftdi_sio into a generic fifo-based driver, which lowers CPU usage
significantly for small writes while retaining maximum throughput.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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Johan Hovold authored and Greg Kroah-Hartman committed May 20, 2010
1 parent 27c7acf commit c23e5fc
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Showing 4 changed files with 48 additions and 176 deletions.
7 changes: 3 additions & 4 deletions drivers/usb/serial/aircable.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -84,9 +84,10 @@ static const struct usb_device_id id_table[] = {
MODULE_DEVICE_TABLE(usb, id_table);

static int aircable_prepare_write_buffer(struct usb_serial_port *port,
void **dest, size_t size, const void *src, size_t count)
void *dest, size_t size)
{
unsigned char *buf = *dest;
int count;
unsigned char *buf = dest;

count = kfifo_out_locked(&port->write_fifo, buf + HCI_HEADER_LENGTH,
size - HCI_HEADER_LENGTH, &port->lock);
Expand Down Expand Up @@ -185,8 +186,6 @@ static struct usb_serial_driver aircable_device = {
.id_table = id_table,
.num_ports = 1,
.bulk_out_size = HCI_COMPLETE_FRAME,
/* Must modify prepare_write_buffer if multi_urb_write is changed. */
.multi_urb_write = 0,
.probe = aircable_probe,
.process_read_urb = aircable_process_read_urb,
.prepare_write_buffer = aircable_prepare_write_buffer,
Expand Down
59 changes: 21 additions & 38 deletions drivers/usb/serial/ftdi_sio.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -781,7 +781,7 @@ static void ftdi_close(struct usb_serial_port *port);
static void ftdi_dtr_rts(struct usb_serial_port *port, int on);
static void ftdi_process_read_urb(struct urb *urb);
static int ftdi_prepare_write_buffer(struct usb_serial_port *port,
void **dest, size_t size, const void *buf, size_t count);
void *dest, size_t size);
static void ftdi_set_termios(struct tty_struct *tty,
struct usb_serial_port *port, struct ktermios *old);
static int ftdi_tiocmget(struct tty_struct *tty, struct file *file);
Expand All @@ -808,8 +808,7 @@ static struct usb_serial_driver ftdi_sio_device = {
.id_table = id_table_combined,
.num_ports = 1,
.bulk_in_size = 512,
/* Must modify prepare_write_buffer if multi_urb_write is changed. */
.multi_urb_write = 1,
.bulk_out_size = 256,
.probe = ftdi_sio_probe,
.port_probe = ftdi_sio_port_probe,
.port_remove = ftdi_sio_port_remove,
Expand Down Expand Up @@ -1531,15 +1530,6 @@ static int ftdi_sio_port_probe(struct usb_serial_port *port)
quirk->port_probe(priv);

priv->port = port;

/* Free port's existing write urb and transfer buffer. */
if (port->write_urb) {
usb_free_urb(port->write_urb);
port->write_urb = NULL;
}
kfree(port->bulk_out_buffer);
port->bulk_out_buffer = NULL;

usb_set_serial_port_data(port, priv);

ftdi_determine_type(port);
Expand Down Expand Up @@ -1734,8 +1724,7 @@ static void ftdi_close(struct usb_serial_port *port)

dbg("%s", __func__);

/* shutdown our bulk read */
usb_kill_urb(port->read_urb);
usb_serial_generic_close(port);
kref_put(&priv->kref, ftdi_sio_priv_release);
}

Expand All @@ -1747,40 +1736,34 @@ static void ftdi_close(struct usb_serial_port *port)
* The new devices do not require this byte
*/
static int ftdi_prepare_write_buffer(struct usb_serial_port *port,
void **dest, size_t size, const void *src, size_t count)
void *dest, size_t size)
{
struct ftdi_private *priv;
unsigned char *buffer;
int len;
int count;
unsigned long flags;

priv = usb_get_serial_port_data(port);

len = count;
if (priv->chip_type == SIO && count != 0)
len += ((count - 1) / (priv->max_packet_size - 1)) + 1;

buffer = kmalloc(len, GFP_ATOMIC);
if (!buffer) {
dev_err(&port->dev, "%s - could not allocate buffer\n",
__func__);
return -ENOMEM;
}

if (priv->chip_type == SIO) {
int i, msg_len;

for (i = 0; i < len; i += priv->max_packet_size) {
msg_len = min_t(int, len - i, priv->max_packet_size) - 1;
buffer[i] = (msg_len << 2) + 1;
memcpy(&buffer[i + 1], src, msg_len);
src += msg_len;
unsigned char *buffer = dest;
int i, len, c;

count = 0;
spin_lock_irqsave(&port->lock, flags);
for (i = 0; i < size - 1; i += priv->max_packet_size) {
len = min_t(int, size - i, priv->max_packet_size) - 1;
buffer[i] = (len << 2) + 1;
c = kfifo_out(&port->write_fifo, &buffer[i + 1], len);
if (!c)
break;
count += c + 1;
}
spin_unlock_irqrestore(&port->lock, flags);
} else {
memcpy(buffer, src, count);
count = kfifo_out_locked(&port->write_fifo, dest, size,
&port->lock);
}

*dest = buffer;

return count;
}

Expand Down
150 changes: 22 additions & 128 deletions drivers/usb/serial/generic.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -26,8 +26,6 @@

static int debug;

#define MAX_TX_URBS 40

#ifdef CONFIG_USB_SERIAL_GENERIC

static int generic_probe(struct usb_interface *interface,
Expand Down Expand Up @@ -172,90 +170,9 @@ void usb_serial_generic_close(struct usb_serial_port *port)
EXPORT_SYMBOL_GPL(usb_serial_generic_close);

int usb_serial_generic_prepare_write_buffer(struct usb_serial_port *port,
void **dest, size_t size, const void *src, size_t count)
void *dest, size_t size)
{
if (!*dest) {
size = count;
*dest = kmalloc(count, GFP_ATOMIC);
if (!*dest) {
dev_err(&port->dev, "%s - could not allocate buffer\n",
__func__);
return -ENOMEM;
}
}
if (src) {
count = size;
memcpy(*dest, src, size);
} else {
count = kfifo_out_locked(&port->write_fifo, *dest, size,
&port->lock);
}
return count;
}
EXPORT_SYMBOL_GPL(usb_serial_generic_prepare_write_buffer);

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;
void *buffer;
int status;

spin_lock_irqsave(&port->lock, flags);
if (port->tx_urbs == MAX_TX_URBS) {
spin_unlock_irqrestore(&port->lock, flags);
dbg("%s - write limit hit", __func__);
return 0;
}
port->tx_urbs++;
spin_unlock_irqrestore(&port->lock, flags);

urb = usb_alloc_urb(0, GFP_ATOMIC);
if (!urb) {
dev_err(&port->dev, "%s - no free urbs available\n", __func__);
status = -ENOMEM;
goto err_urb;
}

buffer = NULL;
count = min_t(int, count, PAGE_SIZE);
count = port->serial->type->prepare_write_buffer(port, &buffer, 0,
buf, count);
if (count < 0) {
status = count;
goto err_buf;
}
usb_serial_debug_data(debug, &port->dev, __func__, count, buffer);
usb_fill_bulk_urb(urb, port->serial->dev,
usb_sndbulkpipe(port->serial->dev,
port->bulk_out_endpointAddress),
buffer, count,
port->serial->type->write_bulk_callback, port);

status = usb_submit_urb(urb, GFP_ATOMIC);
if (status) {
dev_err(&port->dev, "%s - error submitting urb: %d\n",
__func__, status);
goto err;
}
spin_lock_irqsave(&port->lock, flags);
port->tx_bytes += urb->transfer_buffer_length;
spin_unlock_irqrestore(&port->lock, flags);

usb_free_urb(urb);

return count;
err:
kfree(buffer);
err_buf:
usb_free_urb(urb);
err_urb:
spin_lock_irqsave(&port->lock, flags);
port->tx_urbs--;
spin_unlock_irqrestore(&port->lock, flags);

return status;
return kfifo_out_locked(&port->write_fifo, dest, size, &port->lock);
}

/**
Expand Down Expand Up @@ -286,8 +203,8 @@ static int usb_serial_generic_write_start(struct usb_serial_port *port)

urb = port->write_urbs[i];
count = port->serial->type->prepare_write_buffer(port,
&urb->transfer_buffer,
port->bulk_out_size, NULL, 0);
urb->transfer_buffer,
port->bulk_out_size);
urb->transfer_buffer_length = count;
usb_serial_debug_data(debug, &port->dev, __func__, count,
urb->transfer_buffer);
Expand Down Expand Up @@ -328,7 +245,6 @@ static int usb_serial_generic_write_start(struct usb_serial_port *port)
int usb_serial_generic_write(struct tty_struct *tty,
struct usb_serial_port *port, const unsigned char *buf, int count)
{
struct usb_serial *serial = port->serial;
int result;

dbg("%s - port %d", __func__, port->number);
Expand All @@ -340,23 +256,18 @@ int usb_serial_generic_write(struct tty_struct *tty,
if (!count)
return 0;

if (serial->type->multi_urb_write)
return usb_serial_multi_urb_write(tty, port, buf, count);

count = kfifo_in_locked(&port->write_fifo, buf, count, &port->lock);
result = usb_serial_generic_write_start(port);
if (result)
return result;

if (result >= 0)
result = count;

return result;
return count;
}
EXPORT_SYMBOL_GPL(usb_serial_generic_write);

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;

Expand All @@ -366,10 +277,7 @@ int usb_serial_generic_write_room(struct tty_struct *tty)
return 0;

spin_lock_irqsave(&port->lock, flags);
if (serial->type->multi_urb_write)
room = (MAX_TX_URBS - port->tx_urbs) * PAGE_SIZE;
else
room = kfifo_avail(&port->write_fifo);
room = kfifo_avail(&port->write_fifo);
spin_unlock_irqrestore(&port->lock, flags);

dbg("%s - returns %d", __func__, room);
Expand All @@ -379,7 +287,6 @@ int usb_serial_generic_write_room(struct tty_struct *tty)
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;
unsigned long flags;
int chars;

Expand All @@ -389,10 +296,7 @@ int usb_serial_generic_chars_in_buffer(struct tty_struct *tty)
return 0;

spin_lock_irqsave(&port->lock, flags);
if (serial->type->multi_urb_write)
chars = port->tx_bytes;
else
chars = kfifo_len(&port->write_fifo) + port->tx_bytes;
chars = kfifo_len(&port->write_fifo) + port->tx_bytes;
spin_unlock_irqrestore(&port->lock, flags);

dbg("%s - returns %d", __func__, chars);
Expand Down Expand Up @@ -479,35 +383,25 @@ void usb_serial_generic_write_bulk_callback(struct urb *urb)

dbg("%s - port %d", __func__, port->number);

if (port->serial->type->multi_urb_write) {
kfree(urb->transfer_buffer);
for (i = 0; i < ARRAY_SIZE(port->write_urbs); ++i)
if (port->write_urbs[i] == urb)
break;

spin_lock_irqsave(&port->lock, flags);
port->tx_bytes -= urb->transfer_buffer_length;
port->tx_urbs--;
spin_unlock_irqrestore(&port->lock, flags);
} else {
for (i = 0; i < ARRAY_SIZE(port->write_urbs); ++i)
if (port->write_urbs[i] == urb)
break;
spin_lock_irqsave(&port->lock, flags);
port->tx_bytes -= urb->transfer_buffer_length;
set_bit(i, &port->write_urbs_free);
spin_unlock_irqrestore(&port->lock, flags);

if (status) {
dbg("%s - non-zero urb status: %d", __func__, status);

spin_lock_irqsave(&port->lock, flags);
port->tx_bytes -= urb->transfer_buffer_length;
set_bit(i, &port->write_urbs_free);
kfifo_reset_out(&port->write_fifo);
spin_unlock_irqrestore(&port->lock, flags);

if (status) {
spin_lock_irqsave(&port->lock, flags);
kfifo_reset_out(&port->write_fifo);
spin_unlock_irqrestore(&port->lock, flags);
} else {
usb_serial_generic_write_start(port);
}
} else {
usb_serial_generic_write_start(port);
}

if (status)
dbg("%s - non-zero urb status: %d", __func__, status);

usb_serial_port_softint(port);
}
EXPORT_SYMBOL_GPL(usb_serial_generic_write_bulk_callback);
Expand Down
8 changes: 2 additions & 6 deletions include/linux/usb/serial.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,6 @@ enum port_dev_state {
* @write_urbs: pointers to the bulk out urbs for this port
* @write_urbs_free: status bitmap the for bulk out urbs
* @tx_bytes: number of bytes currently in host stack queues
* @tx_urbs: number of urbs currently in host stack queues
* @bulk_out_endpointAddress: endpoint address for the bulk out pipe for this
* port.
* @flags: usb serial port flags
Expand Down Expand Up @@ -112,7 +111,6 @@ struct usb_serial_port {
__u8 bulk_out_endpointAddress;

int tx_bytes;
int tx_urbs;

unsigned long flags;
wait_queue_head_t write_wait;
Expand Down Expand Up @@ -238,8 +236,6 @@ struct usb_serial_driver {
struct usb_driver *usb_driver;
struct usb_dynids dynids;

unsigned char multi_urb_write:1;

size_t bulk_in_size;
size_t bulk_out_size;

Expand Down Expand Up @@ -291,7 +287,7 @@ struct usb_serial_driver {
void (*process_read_urb)(struct urb *urb);
/* Called by the generic write implementation */
int (*prepare_write_buffer)(struct usb_serial_port *port,
void **dest, size_t size, const void *src, size_t count);
void *dest, size_t size);
};
#define to_usb_serial_driver(d) \
container_of(d, struct usb_serial_driver, driver)
Expand Down Expand Up @@ -345,7 +341,7 @@ extern int usb_serial_generic_submit_read_urb(struct usb_serial_port *port,
gfp_t mem_flags);
extern void usb_serial_generic_process_read_urb(struct urb *urb);
extern int usb_serial_generic_prepare_write_buffer(struct usb_serial_port *port,
void **dest, size_t size, const void *src, size_t count);
void *dest, size_t size);
extern int usb_serial_handle_sysrq_char(struct tty_struct *tty,
struct usb_serial_port *port,
unsigned int ch);
Expand Down

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