USB: increase cdc-acm write throughput

the following patch uses 16 write urbs and a writsize of wMaxPacketSize
* 20.  With this patch I get the maximum througput from my linux system
with 20MB/sec read and 15 MB/sec write (full speed 1 MB/sec both)

I also deleted the flag URB_NO_FSBR for the writeurbs, because this
makes my full speed devices significant slower.
Signed-off-by: NDavid Engraf <david.engraf@netcom.eu>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/class/cdc-acm.c

@@ -31,6 +31,7 @@
  *	v0.23 - use softirq for rx processing, as needed by tty layer
  *	v0.24 - change probe method to evaluate CDC union descriptor
  *	v0.25 - downstream tasks paralelized to maximize throughput
+ *	v0.26 - multiple write urbs, writesize increased
  */
 
 /*
@@ -72,7 +73,7 @@
 /*
  * Version Information
  */
-#define DRIVER_VERSION "v0.25"
+#define DRIVER_VERSION "v0.26"
 #define DRIVER_AUTHOR "Armin Fuerst, Pavel Machek, Johannes Erdfelt, Vojtech Pavlik, David Kubicek"
 #define DRIVER_DESC "USB Abstract Control Model driver for USB modems and ISDN adapters"
 
@@ -118,7 +119,7 @@ static int acm_wb_alloc(struct acm *acm)
 	int i, wbn;
 	struct acm_wb *wb;
 
-	wbn = acm->write_current;
+	wbn = 0;
 	i = 0;
 	for (;;) {
 		wb = &acm->wb[wbn];
@@ -132,11 +133,6 @@ static int acm_wb_alloc(struct acm *acm)
 	}
 }
 
-static void acm_wb_free(struct acm *acm, int wbn)
-{
-	acm->wb[wbn].use = 0;
-}
-
 static int acm_wb_is_avail(struct acm *acm)
 {
 	int i, n;
@@ -156,26 +152,22 @@ static inline int acm_wb_is_used(struct acm *acm, int wbn)
 /*
  * Finish write.
  */
-static void acm_write_done(struct acm *acm)
+static void acm_write_done(struct acm *acm, struct acm_wb *wb)
 {
 	unsigned long flags;
-	int wbn;
 
 	spin_lock_irqsave(&acm->write_lock, flags);
 	acm->write_ready = 1;
-	wbn = acm->write_current;
-	acm_wb_free(acm, wbn);
-	acm->write_current = (wbn + 1) % ACM_NW;
+	wb->use = 0;
 	spin_unlock_irqrestore(&acm->write_lock, flags);
 }
 
 /*
  * Poke write.
  */
-static int acm_write_start(struct acm *acm)
+static int acm_write_start(struct acm *acm, int wbn)
 {
 	unsigned long flags;
-	int wbn;
 	struct acm_wb *wb;
 	int rc;
 
@@ -190,24 +182,24 @@ static int acm_write_start(struct acm *acm)
 		return 0;	/* A white lie */
 	}
 
-	wbn = acm->write_current;
 	if (!acm_wb_is_used(acm, wbn)) {
 		spin_unlock_irqrestore(&acm->write_lock, flags);
 		return 0;
 	}
 	wb = &acm->wb[wbn];
 
+	if(acm_wb_is_avail(acm) <= 1)
 		acm->write_ready = 0;
 	spin_unlock_irqrestore(&acm->write_lock, flags);
 
-	acm->writeurb->transfer_buffer = wb->buf;
-	acm->writeurb->transfer_dma = wb->dmah;
-	acm->writeurb->transfer_buffer_length = wb->len;
-	acm->writeurb->dev = acm->dev;
+	wb->urb->transfer_buffer = wb->buf;
+	wb->urb->transfer_dma = wb->dmah;
+	wb->urb->transfer_buffer_length = wb->len;
+	wb->urb->dev = acm->dev;
 
-	if ((rc = usb_submit_urb(acm->writeurb, GFP_ATOMIC)) < 0) {
+	if ((rc = usb_submit_urb(wb->urb, GFP_ATOMIC)) < 0) {
 		dbg("usb_submit_urb(write bulk) failed: %d", rc);
-		acm_write_done(acm);
+		acm_write_done(acm, wb);
 	}
 	return rc;
 }
@@ -450,12 +442,13 @@ static void acm_rx_tasklet(unsigned long _acm)
 /* data interface wrote those outgoing bytes */
 static void acm_write_bulk(struct urb *urb)
 {
-	struct acm *acm = (struct acm *)urb->context;
+	struct acm *acm;
+	struct acm_wb *wb = (struct acm_wb *)urb->context;
 
 	dbg("Entering acm_write_bulk with status %d", urb->status);
 
-	acm_write_done(acm);
-	acm_write_start(acm);
+	acm = wb->instance;
+	acm_write_done(acm, wb);
 	if (ACM_READY(acm))
 		schedule_work(&acm->work);
 }
@@ -557,7 +550,8 @@ static void acm_tty_unregister(struct acm *acm)
 	usb_put_intf(acm->control);
 	acm_table[acm->minor] = NULL;
 	usb_free_urb(acm->ctrlurb);
-	usb_free_urb(acm->writeurb);
+	for (i = 0; i < ACM_NW; i++)
+		usb_free_urb(acm->wb[i].urb);
 	for (i = 0; i < nr; i++)
 		usb_free_urb(acm->ru[i].urb);
 	kfree(acm->country_codes);
@@ -578,7 +572,8 @@ static void acm_tty_close(struct tty_struct *tty, struct file *filp)
 		if (acm->dev) {
 			acm_set_control(acm, acm->ctrlout = 0);
 			usb_kill_urb(acm->ctrlurb);
-			usb_kill_urb(acm->writeurb);
+			for (i = 0; i < ACM_NW; i++)
+				usb_kill_urb(acm->wb[i].urb);
 			for (i = 0; i < nr; i++)
 				usb_kill_urb(acm->ru[i].urb);
 			usb_autopm_put_interface(acm->control);
@@ -606,7 +601,6 @@ static int acm_tty_write(struct tty_struct *tty, const unsigned char *buf, int c
 	spin_lock_irqsave(&acm->write_lock, flags);
 	if ((wbn = acm_wb_alloc(acm)) < 0) {
 		spin_unlock_irqrestore(&acm->write_lock, flags);
-		acm_write_start(acm);
 		return 0;
 	}
 	wb = &acm->wb[wbn];
@@ -617,7 +611,7 @@ static int acm_tty_write(struct tty_struct *tty, const unsigned char *buf, int c
 	wb->len = count;
 	spin_unlock_irqrestore(&acm->write_lock, flags);
 
-	if ((stat = acm_write_start(acm)) < 0)
+	if ((stat = acm_write_start(acm, wbn)) < 0)
 		return stat;
 	return count;
 }
@@ -977,7 +971,7 @@ static int acm_probe (struct usb_interface *intf,
 
 	ctrlsize = le16_to_cpu(epctrl->wMaxPacketSize);
 	readsize = le16_to_cpu(epread->wMaxPacketSize)* ( quirks == SINGLE_RX_URB ? 1 : 2);
-	acm->writesize = le16_to_cpu(epwrite->wMaxPacketSize);
+	acm->writesize = le16_to_cpu(epwrite->wMaxPacketSize) * 20;
 	acm->control = control_interface;
 	acm->data = data_interface;
 	acm->minor = minor;
@@ -1032,12 +1026,21 @@ static int acm_probe (struct usb_interface *intf,
 			goto alloc_fail7;
 		}
 	}
-	acm->writeurb = usb_alloc_urb(0, GFP_KERNEL);
-	if (!acm->writeurb) {
-		dev_dbg(&intf->dev, "out of memory (writeurb kmalloc)\n");
+	for(i = 0; i < ACM_NW; i++)
+	{
+		struct acm_wb *snd = &(acm->wb[i]);
+
+		if (!(snd->urb = usb_alloc_urb(0, GFP_KERNEL))) {
+			dev_dbg(&intf->dev, "out of memory (write urbs usb_alloc_urb)");
 			goto alloc_fail7;
 		}
 
+		usb_fill_bulk_urb(snd->urb, usb_dev, usb_sndbulkpipe(usb_dev, epwrite->bEndpointAddress),
+				NULL, acm->writesize, acm_write_bulk, snd);
+		snd->urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
+		snd->instance = acm;
+	}
+
 	usb_set_intfdata (intf, acm);
 
 	i = device_create_file(&intf->dev, &dev_attr_bmCapabilities);
@@ -1071,10 +1074,6 @@ static int acm_probe (struct usb_interface *intf,
 	acm->ctrlurb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
 	acm->ctrlurb->transfer_dma = acm->ctrl_dma;
 
-	usb_fill_bulk_urb(acm->writeurb, usb_dev, usb_sndbulkpipe(usb_dev, epwrite->bEndpointAddress),
-			  NULL, acm->writesize, acm_write_bulk, acm);
-	acm->writeurb->transfer_flags |= URB_NO_FSBR | URB_NO_TRANSFER_DMA_MAP;
-
 	dev_info(&intf->dev, "ttyACM%d: USB ACM device\n", minor);
 
 	acm_set_control(acm, acm->ctrlout);
@@ -1092,7 +1091,8 @@ static int acm_probe (struct usb_interface *intf,
 
 	return 0;
 alloc_fail8:
-	usb_free_urb(acm->writeurb);
+	for (i = 0; i < ACM_NW; i++)
+		usb_free_urb(acm->wb[i].urb);
 alloc_fail7:
 	for (i = 0; i < num_rx_buf; i++)
 		usb_buffer_free(usb_dev, acm->readsize, acm->rb[i].base, acm->rb[i].dma);
@@ -1116,7 +1116,8 @@ static void stop_data_traffic(struct acm *acm)
 	tasklet_disable(&acm->urb_task);
 
 	usb_kill_urb(acm->ctrlurb);
-	usb_kill_urb(acm->writeurb);
+	for(i = 0; i < ACM_NW; i++)
+		usb_kill_urb(acm->wb[i].urb);
 	for (i = 0; i < acm->rx_buflimit; i++)
 		usb_kill_urb(acm->ru[i].urb);
 

drivers/usb/class/cdc-acm.h

@@ -59,7 +59,7 @@
  * when processing onlcr, so we only need 2 buffers. These values must be
  * powers of 2.
  */
-#define ACM_NW  2
+#define ACM_NW  16
 #define ACM_NR  16
 
 struct acm_wb {
@@ -67,6 +67,8 @@ struct acm_wb {
 	dma_addr_t dmah;
 	int len;
 	int use;
+	struct urb		*urb;
+	struct acm		*instance;
 };
 
 struct acm_rb {
@@ -88,7 +90,7 @@ struct acm {
 	struct usb_interface *control;			/* control interface */
 	struct usb_interface *data;			/* data interface */
 	struct tty_struct *tty;				/* the corresponding tty */
-	struct urb *ctrlurb, *writeurb;			/* urbs */
+	struct urb *ctrlurb;			/* urbs */
 	u8 *ctrl_buffer;				/* buffers of urbs */
 	dma_addr_t ctrl_dma;				/* dma handles of buffers */
 	u8 *country_codes;				/* country codes from device */
@@ -103,7 +105,6 @@ struct acm {
 	struct list_head spare_read_urbs;
 	struct list_head spare_read_bufs;
 	struct list_head filled_read_bufs;
-	int write_current;				/* current write buffer */
 	int write_used;					/* number of non-empty write buffers */
 	int write_ready;				/* write urb is not running */
 	spinlock_t write_lock;