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>

1 files changed, 62 insertions, 21 deletions

diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
index e4db5ad2bc55..f7403576f99f 100644
--- a/drivers/usb/serial/generic.c
+++ b/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++;
                 }