diff --git a/drivers/usb/gadget/u_serial.c b/drivers/usb/gadget/u_serial.c
index abf9505d3a75e1a5b263d08b742ad33b108d0fa1..6641efa55639c823e1d5f57e33660ccaee4c6518 100644
--- a/drivers/usb/gadget/u_serial.c
+++ b/drivers/usb/gadget/u_serial.c
@@ -52,6 +52,8 @@
* is managed in userspace ... OBEX, PTP, and MTP have been mentioned.
*/
+#define PREFIX "ttyGS"
+
/*
* gserial is the lifecycle interface, used by USB functions
* gs_port is the I/O nexus, used by the tty driver
@@ -100,6 +102,8 @@ struct gs_port {
wait_queue_head_t close_wait; /* wait for last close */
struct list_head read_pool;
+ struct list_head read_queue;
+ unsigned n_read;
struct tasklet_struct push;
struct list_head write_pool;
@@ -367,11 +371,9 @@ __acquires(&port->port_lock)
req->length = len;
list_del(&req->list);
-#ifdef VERBOSE_DEBUG
- pr_debug("%s: %s, len=%d, 0x%02x 0x%02x 0x%02x ...\n",
- __func__, in->name, len, *((u8 *)req->buf),
+ pr_vdebug(PREFIX "%d: tx len=%d, 0x%02x 0x%02x 0x%02x ...\n",
+ port->port_num, len, *((u8 *)req->buf),
*((u8 *)req->buf+1), *((u8 *)req->buf+2));
-#endif
/* Drop lock while we call out of driver; completions
* could be issued while we do so. Disconnection may
@@ -401,56 +403,6 @@ __acquires(&port->port_lock)
return status;
}
-static void gs_rx_push(unsigned long _port)
-{
- struct gs_port *port = (void *)_port;
- struct tty_struct *tty = port->port_tty;
-
- /* With low_latency, tty_flip_buffer_push() doesn't put its
- * real work through a workqueue, so the ldisc has a better
- * chance to keep up with peak USB data rates.
- */
- if (tty) {
- tty_flip_buffer_push(tty);
- wake_up_interruptible(&tty->read_wait);
- }
-}
-
-/*
- * gs_recv_packet
- *
- * Called for each USB packet received. Reads the packet
- * header and stuffs the data in the appropriate tty buffer.
- * Returns 0 if successful, or a negative error number.
- *
- * Called during USB completion routine, on interrupt time.
- * With port_lock.
- */
-static int gs_recv_packet(struct gs_port *port, char *packet, unsigned size)
-{
- unsigned len;
- struct tty_struct *tty;
-
- /* I/O completions can continue for a while after close(), until the
- * request queue empties. Just discard any data we receive, until
- * something reopens this TTY ... as if there were no HW flow control.
- */
- tty = port->port_tty;
- if (tty == NULL) {
- pr_vdebug("%s: ttyGS%d, after close\n",
- __func__, port->port_num);
- return -EIO;
- }
-
- len = tty_insert_flip_string(tty, packet, size);
- if (len > 0)
- tasklet_schedule(&port->push);
- if (len < size)
- pr_debug("%s: ttyGS%d, drop %d bytes\n",
- __func__, port->port_num, size - len);
- return 0;
-}
-
/*
* Context: caller owns port_lock, and port_usb is set
*/
@@ -469,9 +421,9 @@ __acquires(&port->port_lock)
int status;
struct tty_struct *tty;
- /* no more rx if closed or throttled */
+ /* no more rx if closed */
tty = port->port_tty;
- if (!tty || test_bit(TTY_THROTTLED, &tty->flags))
+ if (!tty)
break;
req = list_entry(pool->next, struct usb_request, list);
@@ -500,36 +452,134 @@ __acquires(&port->port_lock)
return started;
}
-static void gs_read_complete(struct usb_ep *ep, struct usb_request *req)
+/*
+ * RX tasklet takes data out of the RX queue and hands it up to the TTY
+ * layer until it refuses to take any more data (or is throttled back).
+ * Then it issues reads for any further data.
+ *
+ * If the RX queue becomes full enough that no usb_request is queued,
+ * the OUT endpoint may begin NAKing as soon as its FIFO fills up.
+ * So QUEUE_SIZE packets plus however many the FIFO holds (usually two)
+ * can be buffered before the TTY layer's buffers (currently 64 KB).
+ */
+static void gs_rx_push(unsigned long _port)
{
- int status;
- struct gs_port *port = ep->driver_data;
+ struct gs_port *port = (void *)_port;
+ struct tty_struct *tty;
+ struct list_head *queue = &port->read_queue;
+ bool disconnect = false;
+ bool do_push = false;
- spin_lock(&port->port_lock);
- list_add(&req->list, &port->read_pool);
+ /* hand any queued data to the tty */
+ spin_lock_irq(&port->port_lock);
+ tty = port->port_tty;
+ while (!list_empty(queue)) {
+ struct usb_request *req;
- switch (req->status) {
- case 0:
- /* normal completion */
- status = gs_recv_packet(port, req->buf, req->actual);
- if (status && status != -EIO)
- pr_debug("%s: %s %s err %d\n",
- __func__, "recv", ep->name, status);
- gs_start_rx(port);
- break;
+ req = list_first_entry(queue, struct usb_request, list);
- case -ESHUTDOWN:
- /* disconnect */
- pr_vdebug("%s: %s shutdown\n", __func__, ep->name);
- break;
+ /* discard data if tty was closed */
+ if (!tty)
+ goto recycle;
- default:
- /* presumably a transient fault */
- pr_warning("%s: unexpected %s status %d\n",
- __func__, ep->name, req->status);
- gs_start_rx(port);
- break;
+ /* leave data queued if tty was rx throttled */
+ if (test_bit(TTY_THROTTLED, &tty->flags))
+ break;
+
+ switch (req->status) {
+ case -ESHUTDOWN:
+ disconnect = true;
+ pr_vdebug(PREFIX "%d: shutdown\n", port->port_num);
+ break;
+
+ default:
+ /* presumably a transient fault */
+ pr_warning(PREFIX "%d: unexpected RX status %d\n",
+ port->port_num, req->status);
+ /* FALLTHROUGH */
+ case 0:
+ /* normal completion */
+ break;
+ }
+
+ /* push data to (open) tty */
+ if (req->actual) {
+ char *packet = req->buf;
+ unsigned size = req->actual;
+ unsigned n;
+ int count;
+
+ /* we may have pushed part of this packet already... */
+ n = port->n_read;
+ if (n) {
+ packet += n;
+ size -= n;
+ }
+
+ count = tty_insert_flip_string(tty, packet, size);
+ if (count)
+ do_push = true;
+ if (count != size) {
+ /* stop pushing; TTY layer can't handle more */
+ port->n_read += count;
+ pr_vdebug(PREFIX "%d: rx block %d/%d\n",
+ port->port_num,
+ count, req->actual);
+ break;
+ }
+ port->n_read = 0;
+ }
+recycle:
+ list_move(&req->list, &port->read_pool);
+ }
+
+ /* Push from tty to ldisc; this is immediate with low_latency, and
+ * may trigger callbacks to this driver ... so drop the spinlock.
+ */
+ if (tty && do_push) {
+ spin_unlock_irq(&port->port_lock);
+ tty_flip_buffer_push(tty);
+ wake_up_interruptible(&tty->read_wait);
+ spin_lock_irq(&port->port_lock);
+
+ /* tty may have been closed */
+ tty = port->port_tty;
}
+
+
+ /* We want our data queue to become empty ASAP, keeping data
+ * in the tty and ldisc (not here). If we couldn't push any
+ * this time around, there may be trouble unless there's an
+ * implicit tty_unthrottle() call on its way...
+ *
+ * REVISIT we should probably add a timer to keep the tasklet
+ * from starving ... but it's not clear that case ever happens.
+ */
+ if (!list_empty(queue) && tty) {
+ if (!test_bit(TTY_THROTTLED, &tty->flags)) {
+ if (do_push)
+ tasklet_schedule(&port->push);
+ else
+ pr_warning(PREFIX "%d: RX not scheduled?\n",
+ port->port_num);
+ }
+ }
+
+ /* If we're still connected, refill the USB RX queue. */
+ if (!disconnect && port->port_usb)
+ gs_start_rx(port);
+
+ spin_unlock_irq(&port->port_lock);
+}
+
+static void gs_read_complete(struct usb_ep *ep, struct usb_request *req)
+{
+ struct gs_port *port = ep->driver_data;
+
+ /* Queue all received data until the tty layer is ready for it. */
+ spin_lock(&port->port_lock);
+ list_add_tail(&req->list, &port->read_queue);
+ tasklet_schedule(&port->push);
spin_unlock(&port->port_lock);
}
@@ -625,6 +675,7 @@ static int gs_start_io(struct gs_port *port)
}
/* queue read requests */
+ port->n_read = 0;
started = gs_start_rx(port);
/* unblock any pending writes into our circular buffer */
@@ -633,9 +684,10 @@ static int gs_start_io(struct gs_port *port)
} else {
gs_free_requests(ep, head);
gs_free_requests(port->port_usb->in, &port->write_pool);
+ status = -EIO;
}
- return started ? 0 : status;
+ return status;
}
/*-------------------------------------------------------------------------*/
@@ -809,8 +861,6 @@ static void gs_close(struct tty_struct *tty, struct file *file)
else
gs_buf_clear(&port->port_write_buf);
- tasklet_kill(&port->push);
-
tty->driver_data = NULL;
port->port_tty = NULL;
@@ -911,15 +961,17 @@ static void gs_unthrottle(struct tty_struct *tty)
{
struct gs_port *port = tty->driver_data;
unsigned long flags;
- unsigned started = 0;
spin_lock_irqsave(&port->port_lock, flags);
- if (port->port_usb)
- started = gs_start_rx(port);
+ if (port->port_usb) {
+ /* Kickstart read queue processing. We don't do xon/xoff,
+ * rts/cts, or other handshaking with the host, but if the
+ * read queue backs up enough we'll be NAKing OUT packets.
+ */
+ tasklet_schedule(&port->push);
+ pr_vdebug(PREFIX "%d: unthrottle\n", port->port_num);
+ }
spin_unlock_irqrestore(&port->port_lock, flags);
-
- pr_vdebug("gs_unthrottle: ttyGS%d, %d packets\n",
- port->port_num, started);
}
static const struct tty_operations gs_tty_ops = {
@@ -953,6 +1005,7 @@ gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
tasklet_init(&port->push, gs_rx_push, (unsigned long) port);
INIT_LIST_HEAD(&port->read_pool);
+ INIT_LIST_HEAD(&port->read_queue);
INIT_LIST_HEAD(&port->write_pool);
port->port_num = port_num;
@@ -997,7 +1050,7 @@ int __init gserial_setup(struct usb_gadget *g, unsigned count)
gs_tty_driver->owner = THIS_MODULE;
gs_tty_driver->driver_name = "g_serial";
- gs_tty_driver->name = "ttyGS";
+ gs_tty_driver->name = PREFIX;
/* uses dynamically assigned dev_t values */
gs_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
@@ -1104,6 +1157,8 @@ void gserial_cleanup(void)
ports[i].port = NULL;
mutex_unlock(&ports[i].lock);
+ tasklet_kill(&port->push);
+
/* wait for old opens to finish */
wait_event(port->close_wait, gs_closed(port));
@@ -1241,6 +1296,7 @@ void gserial_disconnect(struct gserial *gser)
if (port->open_count == 0 && !port->openclose)
gs_buf_free(&port->port_write_buf);
gs_free_requests(gser->out, &port->read_pool);
+ gs_free_requests(gser->out, &port->read_queue);
gs_free_requests(gser->in, &port->write_pool);
spin_unlock_irqrestore(&port->port_lock, flags);
}