[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>

1 files changed, 234 insertions, 92 deletions

diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
index 8b2b947b675..1164c52e2c0 100644
--- a/drivers/net/usb/hso.c
+++ b/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 = {