USB: serial: add support for multiple read urbs

Add support for multiple read urbs to generic read implementation.

Use a static array of two read urbs for now which is enough to get a
50% throughput increase in one test setup.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/generic.c

@@ -1,7 +1,7 @@
 /*
  * USB Serial Converter Generic functions
  *
- * Copyright (C) 2010 Johan Hovold (jhovold@gmail.com)
+ * Copyright (C) 2010 - 2011 Johan Hovold (jhovold@gmail.com)
  * Copyright (C) 1999 - 2002 Greg Kroah-Hartman (greg@kroah.com)
  *
  *	This program is free software; you can redistribute it and/or
@@ -132,7 +132,7 @@ int usb_serial_generic_open(struct tty_struct *tty, struct usb_serial_port *port
 
 	/* if we have a bulk endpoint, start reading from it */
 	if (port->bulk_in_size)
-		result = usb_serial_generic_submit_read_urb(port, GFP_KERNEL);
+		result = usb_serial_generic_submit_read_urbs(port, GFP_KERNEL);
 
 	return result;
 }
@@ -157,8 +157,10 @@ static void generic_cleanup(struct usb_serial_port *port)
 			kfifo_reset_out(&port->write_fifo);
 			spin_unlock_irqrestore(&port->lock, flags);
 		}
-		if (port->bulk_in_size)
-			usb_kill_urb(port->read_urb);
+		if (port->bulk_in_size) {
+			for (i = 0; i < ARRAY_SIZE(port->read_urbs); ++i)
+				usb_kill_urb(port->read_urbs[i]);
+		}
 	}
 }
 
@@ -308,19 +310,52 @@ int usb_serial_generic_chars_in_buffer(struct tty_struct *tty)
 	return chars;
 }
 
-int usb_serial_generic_submit_read_urb(struct usb_serial_port *port,
+static int usb_serial_generic_submit_read_urb(struct usb_serial_port *port,
+						int index, gfp_t mem_flags)
+{
+	int res;
+
+	if (!test_and_clear_bit(index, &port->read_urbs_free))
+		return 0;
+
+	dbg("%s - port %d, urb %d\n", __func__, port->number, index);
+
+	res = usb_submit_urb(port->read_urbs[index], mem_flags);
+	if (res) {
+		if (res != -EPERM) {
+			dev_err(&port->dev,
+					"%s - usb_submit_urb failed: %d\n",
+					__func__, res);
+		}
+		set_bit(index, &port->read_urbs_free);
+		return res;
+	}
+
+	return 0;
+}
+
+int usb_serial_generic_submit_read_urbs(struct usb_serial_port *port,
 					gfp_t mem_flags)
 {
-	int result;
+	int res;
+	int i;
 
-	result = usb_submit_urb(port->read_urb, mem_flags);
-	if (result && result != -EPERM) {
-		dev_err(&port->dev, "%s - error submitting urb: %d\n",
-							__func__, result);
+	dbg("%s - port %d", __func__, port->number);
+
+	for (i = 0; i < ARRAY_SIZE(port->read_urbs); ++i) {
+		res = usb_serial_generic_submit_read_urb(port, i, mem_flags);
+		if (res)
+			goto err;
 	}
-	return result;
+
+	return 0;
+err:
+	for (; i >= 0; --i)
+		usb_kill_urb(port->read_urbs[i]);
+
+	return res;
 }
-EXPORT_SYMBOL_GPL(usb_serial_generic_submit_read_urb);
+EXPORT_SYMBOL_GPL(usb_serial_generic_submit_read_urbs);
 
 void usb_serial_generic_process_read_urb(struct urb *urb)
 {
@@ -356,14 +391,19 @@ void usb_serial_generic_read_bulk_callback(struct urb *urb)
 {
 	struct usb_serial_port *port = urb->context;
 	unsigned char *data = urb->transfer_buffer;
-	int status = urb->status;
 	unsigned long flags;
+	int i;
 
-	dbg("%s - port %d", __func__, port->number);
+	for (i = 0; i < ARRAY_SIZE(port->read_urbs); ++i) {
+		if (urb == port->read_urbs[i])
+			break;
+	}
+	set_bit(i, &port->read_urbs_free);
 
-	if (unlikely(status != 0)) {
-		dbg("%s - nonzero read bulk status received: %d",
-		    __func__, status);
+	dbg("%s - port %d, urb %d, len %d\n", __func__, port->number, i,
+							urb->actual_length);
+	if (urb->status) {
+		dbg("%s - non-zero urb status: %d\n", __func__, urb->status);
 		return;
 	}
 
@@ -376,7 +416,7 @@ void usb_serial_generic_read_bulk_callback(struct urb *urb)
 	port->throttled = port->throttle_req;
 	if (!port->throttled) {
 		spin_unlock_irqrestore(&port->lock, flags);
-		usb_serial_generic_submit_read_urb(port, GFP_ATOMIC);
+		usb_serial_generic_submit_read_urb(port, i, GFP_ATOMIC);
 	} else
 		spin_unlock_irqrestore(&port->lock, flags);
 }
@@ -443,7 +483,7 @@ void usb_serial_generic_unthrottle(struct tty_struct *tty)
 	spin_unlock_irq(&port->lock);
 
 	if (was_throttled)
-		usb_serial_generic_submit_read_urb(port, GFP_KERNEL);
+		usb_serial_generic_submit_read_urbs(port, GFP_KERNEL);
 }
 EXPORT_SYMBOL_GPL(usb_serial_generic_unthrottle);
 
@@ -509,8 +549,9 @@ int usb_serial_generic_resume(struct usb_serial *serial)
 		if (!test_bit(ASYNCB_INITIALIZED, &port->port.flags))
 			continue;
 
-		if (port->read_urb) {
-			r = usb_submit_urb(port->read_urb, GFP_NOIO);
+		if (port->bulk_in_size) {
+			r = usb_serial_generic_submit_read_urbs(port,
+								GFP_NOIO);
 			if (r < 0)
 				c++;
 		}

drivers/usb/serial/usb-serial.c

@@ -562,7 +562,8 @@ static void kill_traffic(struct usb_serial_port *port)
 {
 	int i;
 
-	usb_kill_urb(port->read_urb);
+	for (i = 0; i < ARRAY_SIZE(port->read_urbs); ++i)
+		usb_kill_urb(port->read_urbs[i]);
 	for (i = 0; i < ARRAY_SIZE(port->write_urbs); ++i)
 		usb_kill_urb(port->write_urbs[i]);
 	/*
@@ -594,15 +595,17 @@ static void port_release(struct device *dev)
 	kill_traffic(port);
 	cancel_work_sync(&port->work);
 
-	usb_free_urb(port->read_urb);
 	usb_free_urb(port->interrupt_in_urb);
 	usb_free_urb(port->interrupt_out_urb);
+	for (i = 0; i < ARRAY_SIZE(port->read_urbs); ++i) {
+		usb_free_urb(port->read_urbs[i]);
+		kfree(port->bulk_in_buffers[i]);
+	}
 	for (i = 0; i < ARRAY_SIZE(port->write_urbs); ++i) {
 		usb_free_urb(port->write_urbs[i]);
 		kfree(port->bulk_out_buffers[i]);
 	}
 	kfifo_free(&port->write_fifo);
-	kfree(port->bulk_in_buffer);
 	kfree(port->interrupt_in_buffer);
 	kfree(port->interrupt_out_buffer);
 	kfree(port);
@@ -721,6 +724,7 @@ int usb_serial_probe(struct usb_interface *interface,
 	unsigned int minor;
 	int buffer_size;
 	int i;
+	int j;
 	int num_interrupt_in = 0;
 	int num_interrupt_out = 0;
 	int num_bulk_in = 0;
@@ -903,31 +907,39 @@ int usb_serial_probe(struct usb_interface *interface,
 	for (i = 0; i < num_bulk_in; ++i) {
 		endpoint = bulk_in_endpoint[i];
 		port = serial->port[i];
-		port->read_urb = usb_alloc_urb(0, GFP_KERNEL);
-		if (!port->read_urb) {
-			dev_err(&interface->dev, "No free urbs available\n");
-			goto probe_error;
-		}
 		buffer_size = max_t(int, serial->type->bulk_in_size,
 				usb_endpoint_maxp(endpoint));
 		port->bulk_in_size = buffer_size;
 		port->bulk_in_endpointAddress = endpoint->bEndpointAddress;
-		port->bulk_in_buffer = kmalloc(buffer_size, GFP_KERNEL);
-		if (!port->bulk_in_buffer) {
-			dev_err(&interface->dev,
+
+		for (j = 0; j < ARRAY_SIZE(port->read_urbs); ++j) {
+			set_bit(j, &port->read_urbs_free);
+			port->read_urbs[j] = usb_alloc_urb(0, GFP_KERNEL);
+			if (!port->read_urbs[j]) {
+				dev_err(&interface->dev,
+						"No free urbs available\n");
+				goto probe_error;
+			}
+			port->bulk_in_buffers[j] = kmalloc(buffer_size,
+								GFP_KERNEL);
+			if (!port->bulk_in_buffers[j]) {
+				dev_err(&interface->dev,
 					"Couldn't allocate bulk_in_buffer\n");
-			goto probe_error;
-		}
-		usb_fill_bulk_urb(port->read_urb, dev,
-				usb_rcvbulkpipe(dev,
+				goto probe_error;
+			}
+			usb_fill_bulk_urb(port->read_urbs[j], dev,
+					usb_rcvbulkpipe(dev,
 						endpoint->bEndpointAddress),
-				port->bulk_in_buffer, buffer_size,
-				serial->type->read_bulk_callback, port);
+					port->bulk_in_buffers[j], buffer_size,
+					serial->type->read_bulk_callback,
+					port);
+		}
+
+		port->read_urb = port->read_urbs[0];
+		port->bulk_in_buffer = port->bulk_in_buffers[0];
 	}
 
 	for (i = 0; i < num_bulk_out; ++i) {
-		int j;
-
 		endpoint = bulk_out_endpoint[i];
 		port = serial->port[i];
 		if (kfifo_alloc(&port->write_fifo, PAGE_SIZE, GFP_KERNEL))

include/linux/usb/serial.h

@@ -58,6 +58,9 @@ enum port_dev_state {
  * @read_urb: pointer to the bulk in struct urb for this port.
  * @bulk_in_endpointAddress: endpoint address for the bulk in pipe for this
  *	port.
+ * @bulk_in_buffers: pointers to the bulk in buffers for this port
+ * @read_urbs: pointers to the bulk in urbs for this port
+ * @read_urbs_free: status bitmap the for bulk in urbs
  * @bulk_out_buffer: pointer to the bulk out buffer for this port.
  * @bulk_out_size: the size of the bulk_out_buffer, in bytes.
  * @write_urb: pointer to the bulk out struct urb for this port.
@@ -98,6 +101,10 @@ struct usb_serial_port {
 	struct urb		*read_urb;
 	__u8			bulk_in_endpointAddress;
 
+	unsigned char		*bulk_in_buffers[2];
+	struct urb		*read_urbs[2];
+	unsigned long		read_urbs_free;
+
 	unsigned char		*bulk_out_buffer;
 	int			bulk_out_size;
 	struct urb		*write_urb;
@@ -338,7 +345,7 @@ extern void usb_serial_generic_disconnect(struct usb_serial *serial);
 extern void usb_serial_generic_release(struct usb_serial *serial);
 extern int usb_serial_generic_register(int debug);
 extern void usb_serial_generic_deregister(void);
-extern int usb_serial_generic_submit_read_urb(struct usb_serial_port *port,
+extern int usb_serial_generic_submit_read_urbs(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,