[netdrvr] usb/hso: throttle to prevent loss of serial data

Patch to stop loss of characters on the hso modems,
this patch throttles & unthrottles the modem by
not putting out urbs until the tty/line discipline layer
has enough space for newly received packets.
serial ports. This is required for firmware diagnostics
being done at Option.
Signed-off-by: Denis Joseph Barrow <D.Barow@option.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/net/usb/hso.c

@@ -92,9 +92,6 @@
 
 #define	HSO_NET_TX_TIMEOUT		(HZ*10)
 
-/* Serial port defines and structs. */
-#define HSO_SERIAL_FLAG_RX_SENT		0
-
 #define HSO_SERIAL_MAGIC		0x48534f31
 
 /* Number of ttys to handle */
@@ -179,6 +176,12 @@ struct hso_net {
 	unsigned long flags;
 };
 
+enum rx_ctrl_state{
+	RX_IDLE,
+	RX_SENT,
+	RX_PENDING
+};
+
 struct hso_serial {
 	struct hso_device *parent;
 	int magic;
@@ -205,7 +208,7 @@ struct hso_serial {
 	struct usb_endpoint_descriptor *in_endp;
 	struct usb_endpoint_descriptor *out_endp;
 
-	unsigned long flags;
+	enum rx_ctrl_state rx_state;
 	u8 rts_state;
 	u8 dtr_state;
 	unsigned tx_urb_used:1;
@@ -216,6 +219,15 @@ struct hso_serial {
 	spinlock_t serial_lock;
 
 	int (*write_data) (struct hso_serial *serial);
+	/* Hacks required to get flow control
+	 * working on the serial receive buffers
+	 * so as not to drop characters on the floor.
+	 */
+	int  curr_rx_urb_idx;
+	u16  curr_rx_urb_offset;
+	u8   rx_urb_filled[MAX_RX_URBS];
+	struct tasklet_struct unthrottle_tasklet;
+	struct work_struct    retry_unthrottle_workqueue;
 };
 
 struct hso_device {
@@ -271,7 +283,7 @@ struct hso_device {
 static int hso_serial_tiocmset(struct tty_struct *tty, struct file *file,
 			       unsigned int set, unsigned int clear);
 static void ctrl_callback(struct urb *urb);
-static void put_rxbuf_data(struct urb *urb, struct hso_serial *serial);
+static int put_rxbuf_data(struct urb *urb, struct hso_serial *serial);
 static void hso_kick_transmit(struct hso_serial *serial);
 /* Helper functions */
 static int hso_mux_submit_intr_urb(struct hso_shared_int *mux_int,
@@ -287,6 +299,8 @@ static int hso_start_net_device(struct hso_device *hso_dev);
 static void hso_free_shared_int(struct hso_shared_int *shared_int);
 static int hso_stop_net_device(struct hso_device *hso_dev);
 static void hso_serial_ref_free(struct kref *ref);
+static void hso_std_serial_read_bulk_callback(struct urb *urb);
+static int hso_mux_serial_read(struct hso_serial *serial);
 static void async_get_intf(struct work_struct *data);
 static void async_put_intf(struct work_struct *data);
 static int hso_put_activity(struct hso_device *hso_dev);
@@ -458,6 +472,17 @@ static ssize_t hso_sysfs_show_porttype(struct device *dev,
 }
 static DEVICE_ATTR(hsotype, S_IRUGO, hso_sysfs_show_porttype, NULL);
 
+static int hso_urb_to_index(struct hso_serial *serial, struct urb *urb)
+{
+	int idx;
+
+	for (idx = 0; idx < serial->num_rx_urbs; idx++)
+		if (serial->rx_urb[idx] == urb)
+			return idx;
+	dev_err(serial->parent->dev, "hso_urb_to_index failed\n");
+	return -1;
+}
+
 /* converts mux value to a port spec value */
 static u32 hso_mux_to_port(int mux)
 {
@@ -1039,6 +1064,158 @@ static void _hso_serial_set_termios(struct tty_struct *tty,
 	return;
 }
 
+static void hso_resubmit_rx_bulk_urb(struct hso_serial *serial, struct urb *urb)
+{
+	int result;
+#ifdef CONFIG_HSO_AUTOPM
+	usb_mark_last_busy(urb->dev);
+#endif
+	/* We are done with this URB, resubmit it. Prep the USB to wait for
+	 * another frame */
+	usb_fill_bulk_urb(urb, serial->parent->usb,
+			  usb_rcvbulkpipe(serial->parent->usb,
+					  serial->in_endp->
+					  bEndpointAddress & 0x7F),
+			  urb->transfer_buffer, serial->rx_data_length,
+			  hso_std_serial_read_bulk_callback, serial);
+	/* Give this to the USB subsystem so it can tell us when more data
+	 * arrives. */
+	result = usb_submit_urb(urb, GFP_ATOMIC);
+	if (result) {
+		dev_err(&urb->dev->dev, "%s failed submit serial rx_urb %d\n",
+			__func__, result);
+	}
+}
+
+
+
+
+static void put_rxbuf_data_and_resubmit_bulk_urb(struct hso_serial *serial)
+{
+	int count;
+	struct urb *curr_urb;
+
+	while (serial->rx_urb_filled[serial->curr_rx_urb_idx]) {
+		curr_urb = serial->rx_urb[serial->curr_rx_urb_idx];
+		count = put_rxbuf_data(curr_urb, serial);
+		if (count == -1)
+			return;
+		if (count == 0) {
+			serial->curr_rx_urb_idx++;
+			if (serial->curr_rx_urb_idx >= serial->num_rx_urbs)
+				serial->curr_rx_urb_idx = 0;
+			hso_resubmit_rx_bulk_urb(serial, curr_urb);
+		}
+	}
+}
+
+static void put_rxbuf_data_and_resubmit_ctrl_urb(struct hso_serial *serial)
+{
+	int count = 0;
+	struct urb *urb;
+
+	urb = serial->rx_urb[0];
+	if (serial->open_count > 0) {
+		count = put_rxbuf_data(urb, serial);
+		if (count == -1)
+			return;
+	}
+	/* Re issue a read as long as we receive data. */
+
+	if (count == 0 && ((urb->actual_length != 0) ||
+			   (serial->rx_state == RX_PENDING))) {
+		serial->rx_state = RX_SENT;
+		hso_mux_serial_read(serial);
+	} else
+		serial->rx_state = RX_IDLE;
+}
+
+
+/* read callback for Diag and CS port */
+static void hso_std_serial_read_bulk_callback(struct urb *urb)
+{
+	struct hso_serial *serial = urb->context;
+	int status = urb->status;
+
+	/* sanity check */
+	if (!serial) {
+		D1("serial == NULL");
+		return;
+	} else if (status) {
+		log_usb_status(status, __func__);
+		return;
+	}
+
+	D4("\n--- Got serial_read_bulk callback %02x ---", status);
+	D1("Actual length = %d\n", urb->actual_length);
+	DUMP1(urb->transfer_buffer, urb->actual_length);
+
+	/* Anyone listening? */
+	if (serial->open_count == 0)
+		return;
+
+	if (status == 0) {
+		if (serial->parent->port_spec & HSO_INFO_CRC_BUG) {
+			u32 rest;
+			u8 crc_check[4] = { 0xDE, 0xAD, 0xBE, 0xEF };
+			rest =
+			    urb->actual_length %
+			    serial->in_endp->wMaxPacketSize;
+			if (((rest == 5) || (rest == 6))
+			    && !memcmp(((u8 *) urb->transfer_buffer) +
+				       urb->actual_length - 4, crc_check, 4)) {
+				urb->actual_length -= 4;
+			}
+		}
+		/* Valid data, handle RX data */
+		spin_lock(&serial->serial_lock);
+		serial->rx_urb_filled[hso_urb_to_index(serial, urb)] = 1;
+		put_rxbuf_data_and_resubmit_bulk_urb(serial);
+		spin_unlock(&serial->serial_lock);
+	} else if (status == -ENOENT || status == -ECONNRESET) {
+		/* Unlinked - check for throttled port. */
+		D2("Port %d, successfully unlinked urb", serial->minor);
+		spin_lock(&serial->serial_lock);
+		serial->rx_urb_filled[hso_urb_to_index(serial, urb)] = 0;
+		hso_resubmit_rx_bulk_urb(serial, urb);
+		spin_unlock(&serial->serial_lock);
+	} else {
+		D2("Port %d, status = %d for read urb", serial->minor, status);
+		return;
+	}
+}
+
+/*
+ * This needs to be a tasklet otherwise we will
+ * end up recursively calling this function.
+ */
+void hso_unthrottle_tasklet(struct hso_serial *serial)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&serial->serial_lock, flags);
+	if ((serial->parent->port_spec & HSO_INTF_MUX))
+		put_rxbuf_data_and_resubmit_ctrl_urb(serial);
+	else
+		put_rxbuf_data_and_resubmit_bulk_urb(serial);
+	spin_unlock_irqrestore(&serial->serial_lock, flags);
+}
+
+static	void hso_unthrottle(struct tty_struct *tty)
+{
+	struct hso_serial *serial = get_serial_by_tty(tty);
+
+	tasklet_hi_schedule(&serial->unthrottle_tasklet);
+}
+
+void hso_unthrottle_workfunc(struct work_struct *work)
+{
+	struct hso_serial *serial =
+	    container_of(work, struct hso_serial,
+			 retry_unthrottle_workqueue);
+	hso_unthrottle_tasklet(serial);
+}
+
 /* open the requested serial port */
 static int hso_serial_open(struct tty_struct *tty, struct file *filp)
 {
@@ -1064,13 +1241,18 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
 	tty->driver_data = serial;
 	serial->tty = tty;
 
-	/* check for port allready opened, if not set the termios */
+	/* check for port already opened, if not set the termios */
 	serial->open_count++;
 	if (serial->open_count == 1) {
 		tty->low_latency = 1;
-		serial->flags = 0;
+		serial->rx_state = RX_IDLE;
 		/* Force default termio settings */
 		_hso_serial_set_termios(tty, NULL);
+		tasklet_init(&serial->unthrottle_tasklet,
+			     (void (*)(unsigned long))hso_unthrottle_tasklet,
+			     (unsigned long)serial);
+		INIT_WORK(&serial->retry_unthrottle_workqueue,
+			  hso_unthrottle_workfunc);
 		result = hso_start_serial_device(serial->parent, GFP_KERNEL);
 		if (result) {
 			hso_stop_serial_device(serial->parent);
@@ -1117,9 +1299,13 @@ static void hso_serial_close(struct tty_struct *tty, struct file *filp)
 		}
 		if (!usb_gone)
 			hso_stop_serial_device(serial->parent);
+		tasklet_kill(&serial->unthrottle_tasklet);
+		cancel_work_sync(&serial->retry_unthrottle_workqueue);
 	}
+
 	if (!usb_gone)
 		usb_autopm_put_interface(serial->parent->interface);
+
 	mutex_unlock(&serial->parent->mutex);
 }
 
@@ -1422,15 +1608,21 @@ static void intr_callback(struct urb *urb)
 								   (1 << i));
 			if (serial != NULL) {
 				D1("Pending read interrupt on port %d\n", i);
-				if (!test_and_set_bit(HSO_SERIAL_FLAG_RX_SENT,
-						      &serial->flags)) {
+				spin_lock(&serial->serial_lock);
+				if (serial->rx_state == RX_IDLE) {
 					/* Setup and send a ctrl req read on
 					 * port i */
-					hso_mux_serial_read(serial);
+				if (!serial->rx_urb_filled[0]) {
+						serial->rx_state = RX_SENT;
+						hso_mux_serial_read(serial);
+					} else
+						serial->rx_state = RX_PENDING;
+
 				} else {
 					D1("Already pending a read on "
 					   "port %d\n", i);
 				}
+				spin_unlock(&serial->serial_lock);
 			}
 		}
 	}
@@ -1532,16 +1724,10 @@ static void ctrl_callback(struct urb *urb)
 	if (req->bRequestType ==
 	    (USB_DIR_IN | USB_TYPE_OPTION_VENDOR | USB_RECIP_INTERFACE)) {
 		/* response to a read command */
-		if (serial->open_count > 0) {
-			/* handle RX data the normal way */
-			put_rxbuf_data(urb, serial);
-		}
-
-		/* Re issue a read as long as we receive data. */
-		if (urb->actual_length != 0)
-			hso_mux_serial_read(serial);
-		else
-			clear_bit(HSO_SERIAL_FLAG_RX_SENT, &serial->flags);
+		serial->rx_urb_filled[0] = 1;
+		spin_lock(&serial->serial_lock);
+		put_rxbuf_data_and_resubmit_ctrl_urb(serial);
+		spin_unlock(&serial->serial_lock);
 	} else {
 		hso_put_activity(serial->parent);
 		if (serial->tty)
@@ -1552,91 +1738,42 @@ static void ctrl_callback(struct urb *urb)
 }
 
 /* handle RX data for serial port */
-static void put_rxbuf_data(struct urb *urb, struct hso_serial *serial)
+static int put_rxbuf_data(struct urb *urb, struct hso_serial *serial)
 {
 	struct tty_struct *tty = serial->tty;
-
+	int write_length_remaining = 0;
+	int curr_write_len;
 	/* Sanity check */
 	if (urb == NULL || serial == NULL) {
 		D1("serial = NULL");
-		return;
+		return -2;
 	}
 
 	/* Push data to tty */
-	if (tty && urb->actual_length) {
+	if (tty) {
+		write_length_remaining = urb->actual_length -
+			serial->curr_rx_urb_offset;
 		D1("data to push to tty");
-		tty_insert_flip_string(tty, urb->transfer_buffer,
-				       urb->actual_length);
-		tty_flip_buffer_push(tty);
-	}
-}
-
-/* read callback for Diag and CS port */
-static void hso_std_serial_read_bulk_callback(struct urb *urb)
-{
-	struct hso_serial *serial = urb->context;
-	int result;
-	int status = urb->status;
-
-	/* sanity check */
-	if (!serial) {
-		D1("serial == NULL");
-		return;
-	} else if (status) {
-		log_usb_status(status, __func__);
-		return;
-	}
-
-	D4("\n--- Got serial_read_bulk callback %02x ---", status);
-	D1("Actual length = %d\n", urb->actual_length);
-	DUMP1(urb->transfer_buffer, urb->actual_length);
-
-	/* Anyone listening? */
-	if (serial->open_count == 0)
-		return;
-
-	if (status == 0) {
-		if (serial->parent->port_spec & HSO_INFO_CRC_BUG) {
-			u32 rest;
-			u8 crc_check[4] = { 0xDE, 0xAD, 0xBE, 0xEF };
-			rest =
-			    urb->actual_length %
-			    serial->in_endp->wMaxPacketSize;
-			if (((rest == 5) || (rest == 6))
-			    && !memcmp(((u8 *) urb->transfer_buffer) +
-				       urb->actual_length - 4, crc_check, 4)) {
-				urb->actual_length -= 4;
-			}
+		while (write_length_remaining) {
+			if (test_bit(TTY_THROTTLED, &tty->flags))
+				return -1;
+			curr_write_len =  tty_insert_flip_string
+				(tty, urb->transfer_buffer +
+				 serial->curr_rx_urb_offset,
+				 write_length_remaining);
+			serial->curr_rx_urb_offset += curr_write_len;
+			write_length_remaining -= curr_write_len;
+			tty_flip_buffer_push(tty);
 		}
-		/* Valid data, handle RX data */
-		put_rxbuf_data(urb, serial);
-	} else if (status == -ENOENT || status == -ECONNRESET) {
-		/* Unlinked - check for throttled port. */
-		D2("Port %d, successfully unlinked urb", serial->minor);
-	} else {
-		D2("Port %d, status = %d for read urb", serial->minor, status);
-		return;
 	}
-
-	usb_mark_last_busy(urb->dev);
-
-	/* We are done with this URB, resubmit it. Prep the USB to wait for
-	 * another frame */
-	usb_fill_bulk_urb(urb, serial->parent->usb,
-			  usb_rcvbulkpipe(serial->parent->usb,
-					  serial->in_endp->
-					  bEndpointAddress & 0x7F),
-			  urb->transfer_buffer, serial->rx_data_length,
-			  hso_std_serial_read_bulk_callback, serial);
-	/* Give this to the USB subsystem so it can tell us when more data
-	 * arrives. */
-	result = usb_submit_urb(urb, GFP_ATOMIC);
-	if (result) {
-		dev_err(&urb->dev->dev, "%s failed submit serial rx_urb %d",
-			__func__, result);
+	if (write_length_remaining == 0) {
+		serial->curr_rx_urb_offset = 0;
+		serial->rx_urb_filled[hso_urb_to_index(serial, urb)] = 0;
 	}
+	return write_length_remaining;
 }
 
+
 /* Base driver functions */
 
 static void hso_log_port(struct hso_device *hso_dev)
@@ -1794,9 +1931,13 @@ static int hso_stop_serial_device(struct hso_device *hso_dev)
 		return -ENODEV;
 
 	for (i = 0; i < serial->num_rx_urbs; i++) {
-		if (serial->rx_urb[i])
+		if (serial->rx_urb[i]) {
 				usb_kill_urb(serial->rx_urb[i]);
+				serial->rx_urb_filled[i] = 0;
+		}
 	}
+	serial->curr_rx_urb_idx = 0;
+	serial->curr_rx_urb_offset = 0;
 
 	if (serial->tx_urb)
 		usb_kill_urb(serial->tx_urb);
@@ -2741,6 +2882,7 @@ static const struct tty_operations hso_serial_ops = {
 	.chars_in_buffer = hso_serial_chars_in_buffer,
 	.tiocmget = hso_serial_tiocmget,
 	.tiocmset = hso_serial_tiocmset,
+	.unthrottle = hso_unthrottle
 };
 
 static struct usb_driver hso_driver = {