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USB: increase cdc-acm write throughput
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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: David Engraf <david.engraf@netcom.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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David Engraf authored and Greg Kroah-Hartman committed Apr 25, 2008
1 parent 28d1dfa commit e4cf3aa
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Showing 2 changed files with 45 additions and 43 deletions.
81 changes: 41 additions & 40 deletions drivers/usb/class/cdc-acm.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
*/

/*
Expand Down Expand Up @@ -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"

Expand Down Expand Up @@ -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];
Expand All @@ -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;
Expand All @@ -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;

Expand All @@ -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];

acm->write_ready = 0;
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;
}
Expand Down Expand Up @@ -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);
}
Expand Down Expand Up @@ -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);
Expand All @@ -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);
Expand Down Expand Up @@ -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];
Expand All @@ -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;
}
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -1032,10 +1026,19 @@ 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");
goto alloc_fail7;
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);
Expand Down Expand Up @@ -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);
Expand All @@ -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);
Expand All @@ -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);

Expand Down
7 changes: 4 additions & 3 deletions drivers/usb/class/cdc-acm.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -59,14 +59,16 @@
* 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 {
unsigned char *buf;
dma_addr_t dmah;
int len;
int use;
struct urb *urb;
struct acm *instance;
};

struct acm_rb {
Expand All @@ -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 */
Expand All @@ -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;
Expand Down

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