USB: ftdi_sio: re-implement read processing

- Re-structure read processing.
 - Kill obsolete work queue and always push to tty in completion handler.
 - Use tty_insert_flip_string instead of per character push when
   possible.
 - Fix stalled-read regression in 2.6.31 by using urb status to
   determine when port is closed rather than port count.
 - Fix race with open/close by checking ASYNCB_INITIALIZED in
   unthrottle.
 - Kill private rx_flag and lock and use throttle flags in
   usb_serial_port instead.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 131 insertions, 252 deletions

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 75c84d9b080d..9c60d6d4908a 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -76,12 +76,7 @@ struct ftdi_private {
         unsigned long last_dtr_rts;     /* saved modem control outputs */
         wait_queue_head_t delta_msr_wait; /* Used for TIOCMIWAIT */
         char prev_status, diff_status;        /* Used for TIOCMIWAIT */
-        __u8 rx_flags;          /* receive state flags (throttling) */
-        spinlock_t rx_lock;     /* spinlock for receive state */
-        struct delayed_work rx_work;
         struct usb_serial_port *port;
-        int rx_processed;
-
         __u16 interface;        /* FT2232C, FT2232H or FT4232H port interface
                                    (0 for FT232/245) */
 
@@ -736,10 +731,6 @@ static const char *ftdi_chip_name[] = {
 /* Constants for read urb and write urb */
 #define BUFSZ 512
 
-/* rx_flags */
-#define THROTTLED               0x01
-#define ACTUALLY_THROTTLED      0x02
-
 /* Used for TIOCMIWAIT */
 #define FTDI_STATUS_B0_MASK     (FTDI_RS0_CTS | FTDI_RS0_DSR | FTDI_RS0_RI | FTDI_RS0_RLSD)
 #define FTDI_STATUS_B1_MASK     (FTDI_RS_BI)
@@ -762,7 +753,7 @@ static int  ftdi_write_room(struct tty_struct *tty);
 static int  ftdi_chars_in_buffer(struct tty_struct *tty);
 static void ftdi_write_bulk_callback(struct urb *urb);
 static void ftdi_read_bulk_callback(struct urb *urb);
-static void ftdi_process_read(struct work_struct *work);
+static void ftdi_process_read(struct usb_serial_port *port);
 static void ftdi_set_termios(struct tty_struct *tty,
                         struct usb_serial_port *port, struct ktermios *old);
 static int  ftdi_tiocmget(struct tty_struct *tty, struct file *file);
@@ -1525,7 +1516,6 @@ static int ftdi_sio_port_probe(struct usb_serial_port *port)
         }
 
         kref_init(&priv->kref);
-        spin_lock_init(&priv->rx_lock);
         spin_lock_init(&priv->tx_lock);
         init_waitqueue_head(&priv->delta_msr_wait);
         /* This will push the characters through immediately rather
@@ -1547,7 +1537,6 @@ static int ftdi_sio_port_probe(struct usb_serial_port *port)
                 port->read_urb->transfer_buffer_length = BUFSZ;
         }
 
-        INIT_DELAYED_WORK(&priv->rx_work, ftdi_process_read);
         priv->port = port;
 
         /* Free port's existing write urb and transfer buffer. */
@@ -1684,6 +1673,26 @@ static int ftdi_sio_port_remove(struct usb_serial_port *port)
         return 0;
 }
 
+static int ftdi_submit_read_urb(struct usb_serial_port *port, gfp_t mem_flags)
+{
+        struct urb *urb = port->read_urb;
+        struct usb_serial *serial = port->serial;
+        int result;
+
+        usb_fill_bulk_urb(urb, serial->dev,
+                           usb_rcvbulkpipe(serial->dev,
+                                        port->bulk_in_endpointAddress),
+                           urb->transfer_buffer,
+                           urb->transfer_buffer_length,
+                           ftdi_read_bulk_callback, port);
+        result = usb_submit_urb(urb, mem_flags);
+        if (result)
+                dev_err(&port->dev,
+                        "%s - failed submitting read urb, error %d\n",
+                                                        __func__, result);
+        return result;
+}
+
 static int ftdi_open(struct tty_struct *tty, struct usb_serial_port *port)
 { /* ftdi_open */
         struct usb_device *dev = port->serial->dev;
@@ -1717,23 +1726,14 @@ static int ftdi_open(struct tty_struct *tty, struct usb_serial_port *port)
                 ftdi_set_termios(tty, port, tty->termios);
 
         /* Not throttled */
-        spin_lock_irqsave(&priv->rx_lock, flags);
-        priv->rx_flags &= ~(THROTTLED | ACTUALLY_THROTTLED);
-        spin_unlock_irqrestore(&priv->rx_lock, flags);
+        spin_lock_irqsave(&port->lock, flags);
+        port->throttled = 0;
+        port->throttle_req = 0;
+        spin_unlock_irqrestore(&port->lock, flags);
 
         /* Start reading from the device */
-        priv->rx_processed = 0;
-        usb_fill_bulk_urb(port->read_urb, dev,
-                        usb_rcvbulkpipe(dev, port->bulk_in_endpointAddress),
-                        port->read_urb->transfer_buffer,
-                                port->read_urb->transfer_buffer_length,
-                        ftdi_read_bulk_callback, port);
-        result = usb_submit_urb(port->read_urb, GFP_KERNEL);
-        if (result)
-                dev_err(&port->dev,
-                        "%s - failed submitting read urb, error %d\n",
-                        __func__, result);
-        else
+        result = ftdi_submit_read_urb(port, GFP_KERNEL);
+        if (!result)
                 kref_get(&priv->kref);
 
         return result;
@@ -1779,10 +1779,6 @@ static void ftdi_close(struct usb_serial_port *port)
 
         dbg("%s", __func__);
 
-
-        /* cancel any scheduled reading */
-        cancel_delayed_work_sync(&priv->rx_work);
-
         /* shutdown our bulk read */
         usb_kill_urb(port->read_urb);
         kref_put(&priv->kref, ftdi_sio_priv_release);
@@ -2005,236 +2001,121 @@ static int ftdi_chars_in_buffer(struct tty_struct *tty)
         return buffered;
 }
 
-static void ftdi_read_bulk_callback(struct urb *urb)
+static int ftdi_process_packet(struct tty_struct *tty,
+                struct usb_serial_port *port, struct ftdi_private *priv,
+                char *packet, int len)
 {
-        struct usb_serial_port *port = urb->context;
-        struct ftdi_private *priv;
-        int status = urb->status;
-
-        dbg("%s - port %d", __func__, port->number);
-
-        if (port->port.count <= 0)
-                return;
-
-        if (status) {
-                /* This will happen at close every time so it is a dbg not an
-                   err */
-                dbg("(this is ok on close) nonzero read bulk status received: %d", status);
-                goto out;
-        }
-
-        priv = usb_get_serial_port_data(port);
-        ftdi_process_read(&priv->rx_work.work);
-} /* ftdi_read_bulk_callback */
-
-
-static void ftdi_process_read(struct work_struct *work)
-{ /* ftdi_process_read */
-        struct ftdi_private *priv =
-                container_of(work, struct ftdi_private, rx_work.work);
-        struct usb_serial_port *port = priv->port;
-        struct urb *urb;
-        struct tty_struct *tty;
-        char error_flag;
-        unsigned char *data;
-
         int i;
-        int result;
-        int need_flip;
-        int packet_offset;
-        unsigned long flags;
+        char status;
+        char flag;
+        char *ch;
 
         dbg("%s - port %d", __func__, port->number);
 
-        if (port->port.count <= 0)
-                return;
-
-        tty = tty_port_tty_get(&port->port);
-        if (!tty) {
-                dbg("%s - bad tty pointer - exiting", __func__);
-                return;
+        if (len < 2) {
+                dbg("malformed packet");
+                return 0;
         }
 
-        priv = usb_get_serial_port_data(port);
-        if (!priv) {
-                dbg("%s - bad port private data pointer - exiting", __func__);
-                goto out;
+        /* Compare new line status to the old one, signal if different/
+           N.B. packet may be processed more than once, but differences
+           are only processed once.  */
+        status = packet[0] & FTDI_STATUS_B0_MASK;
+        if (status != priv->prev_status) {
+                priv->diff_status |= status ^ priv->prev_status;
+                wake_up_interruptible(&priv->delta_msr_wait);
+                priv->prev_status = status;
         }
 
-        urb = port->read_urb;
-        if (!urb) {
-                dbg("%s - bad read_urb pointer - exiting", __func__);
-                goto out;
+        /*
+         * Although the device uses a bitmask and hence can have multiple
+         * errors on a packet - the order here sets the priority the error is
+         * returned to the tty layer.
+         */
+        flag = TTY_NORMAL;
+        if (packet[1] & FTDI_RS_OE) {
+                flag = TTY_OVERRUN;
+                dbg("OVERRRUN error");
         }
-
-        data = urb->transfer_buffer;
-
-        if (priv->rx_processed) {
-                dbg("%s - already processed: %d bytes, %d remain", __func__,
-                                priv->rx_processed,
-                                urb->actual_length - priv->rx_processed);
-        } else {
-                /* The first two bytes of every read packet are status */
-                if (urb->actual_length > 2)
-                        usb_serial_debug_data(debug, &port->dev, __func__,
-                                                urb->actual_length, data);
-                else
-                        dbg("Status only: %03oo %03oo", data[0], data[1]);
+        if (packet[1] & FTDI_RS_BI) {
+                flag = TTY_BREAK;
+                dbg("BREAK received");
+                usb_serial_handle_break(port);
+        }
+        if (packet[1] & FTDI_RS_PE) {
+                flag = TTY_PARITY;
+                dbg("PARITY error");
+        }
+        if (packet[1] & FTDI_RS_FE) {
+                flag = TTY_FRAME;
+                dbg("FRAMING error");
         }
 
-
-        /* TO DO -- check for hung up line and handle appropriately: */
-        /*   send hangup  */
-        /* See acm.c - you do a tty_hangup  - eg tty_hangup(tty) */
-        /* if CD is dropped and the line is not CLOCAL then we should hangup */
-
-        need_flip = 0;
-        for (packet_offset = priv->rx_processed;
-                packet_offset < urb->actual_length; packet_offset += priv->max_packet_size) {
-                int length;
-
-                /* Compare new line status to the old one, signal if different/
-                   N.B. packet may be processed more than once, but differences
-                   are only processed once.  */
-                char new_status = data[packet_offset + 0] &
-                                                FTDI_STATUS_B0_MASK;
-                if (new_status != priv->prev_status) {
-                        priv->diff_status |=
-                                new_status ^ priv->prev_status;
-                        wake_up_interruptible(&priv->delta_msr_wait);
-                        priv->prev_status = new_status;
-                }
-
-                length = min_t(u32, priv->max_packet_size, urb->actual_length-packet_offset)-2;
-                if (length < 0) {
-                        dev_err(&port->dev, "%s - bad packet length: %d\n",
-                                __func__, length+2);
-                        length = 0;
-                }
-
-                if (priv->rx_flags & THROTTLED) {
-                        dbg("%s - throttled", __func__);
-                        break;
-                }
-                if (tty_buffer_request_room(tty, length) < length) {
-                        /* break out & wait for throttling/unthrottling to
-                           happen */
-                        dbg("%s - receive room low", __func__);
-                        break;
+        len -= 2;
+        if (!len)
+                return 0;       /* status only */
+        ch = packet + 2;
+
+        if (!(port->console && port->sysrq) && flag == TTY_NORMAL)
+                tty_insert_flip_string(tty, ch, len);
+        else {
+                for (i = 0; i < len; i++, ch++) {
+                        if (!usb_serial_handle_sysrq_char(tty, port, *ch))
+                                tty_insert_flip_char(tty, *ch, flag);
                 }
+        }
+        return len;
+}
 
-                /* Handle errors and break */
-                error_flag = TTY_NORMAL;
-                /* Although the device uses a bitmask and hence can have
-                   multiple errors on a packet - the order here sets the
-                   priority the error is returned to the tty layer  */
+static void ftdi_process_read(struct usb_serial_port *port)
+{
+        struct urb *urb = port->read_urb;
+        struct tty_struct *tty;
+        struct ftdi_private *priv = usb_get_serial_port_data(port);
+        char *data = (char *)urb->transfer_buffer;
+        int i;
+        int len;
+        int count = 0;
 
-                if (data[packet_offset+1] & FTDI_RS_OE) {
-                        error_flag = TTY_OVERRUN;
-                        dbg("OVERRRUN error");
-                }
-                if (data[packet_offset+1] & FTDI_RS_BI) {
-                        error_flag = TTY_BREAK;
-                        dbg("BREAK received");
-                        usb_serial_handle_break(port);
-                }
-                if (data[packet_offset+1] & FTDI_RS_PE) {
-                        error_flag = TTY_PARITY;
-                        dbg("PARITY error");
-                }
-                if (data[packet_offset+1] & FTDI_RS_FE) {
-                        error_flag = TTY_FRAME;
-                        dbg("FRAMING error");
-                }
-                if (length > 0) {
-                        for (i = 2; i < length+2; i++) {
-                                /* Note that the error flag is duplicated for
-                                   every character received since we don't know
-                                   which character it applied to */
-                                if (!usb_serial_handle_sysrq_char(tty, port,
-                                                data[packet_offset + i]))
-                                        tty_insert_flip_char(tty,
-                                                data[packet_offset + i],
-                                                error_flag);
-                        }
-                        need_flip = 1;
-                }
+        tty = tty_port_tty_get(&port->port);
+        if (!tty)
+                return;
 
-#ifdef NOT_CORRECT_BUT_KEEPING_IT_FOR_NOW
-                /* if a parity error is detected you get status packets forever
-                   until a character is sent without a parity error.
-                   This doesn't work well since the application receives a
-                   never ending stream of bad data - even though new data
-                   hasn't been sent. Therefore I (bill) have taken this out.
-                   However - this might make sense for framing errors and so on
-                   so I am leaving the code in for now.
-                */
-                else {
-                        if (error_flag != TTY_NORMAL) {
-                                dbg("error_flag is not normal");
-                                /* In this case it is just status - if that is
-                                   an error send a bad character */
-                                if (tty->flip.count >= TTY_FLIPBUF_SIZE)
-                                        tty_flip_buffer_push(tty);
-                                tty_insert_flip_char(tty, 0xff, error_flag);
-                                need_flip = 1;
-                        }
-                }
-#endif
-        } /* "for(packet_offset=0..." */
+        for (i = 0; i < urb->actual_length; i += priv->max_packet_size) {
+                len = min_t(int, urb->actual_length - i, priv->max_packet_size);
+                count += ftdi_process_packet(tty, port, priv, &data[i], len);
+        }
 
-        /* Low latency */
-        if (need_flip)
+        if (count)
                 tty_flip_buffer_push(tty);
+        tty_kref_put(tty);
+}
 
-        if (packet_offset < urb->actual_length) {
-                /* not completely processed - record progress */
-                priv->rx_processed = packet_offset;
-                dbg("%s - incomplete, %d bytes processed, %d remain",
-                                __func__, packet_offset,
-                                urb->actual_length - packet_offset);
-                /* check if we were throttled while processing */
-                spin_lock_irqsave(&priv->rx_lock, flags);
-                if (priv->rx_flags & THROTTLED) {
-                        priv->rx_flags |= ACTUALLY_THROTTLED;
-                        spin_unlock_irqrestore(&priv->rx_lock, flags);
-                        dbg("%s - deferring remainder until unthrottled",
-                                        __func__);
-                        goto out;
-                }
-                spin_unlock_irqrestore(&priv->rx_lock, flags);
-                /* if the port is closed stop trying to read */
-                if (port->port.count > 0)
-                        /* delay processing of remainder */
-                        schedule_delayed_work(&priv->rx_work, 1);
-                else
-                        dbg("%s - port is closed", __func__);
-                goto out;
-        }
-
-        /* urb is completely processed */
-        priv->rx_processed = 0;
+static void ftdi_read_bulk_callback(struct urb *urb)
+{
+        struct usb_serial_port *port = urb->context;
+        unsigned long flags;
 
-        /* if the port is closed stop trying to read */
-        if (port->port.count > 0) {
-                /* Continue trying to always read  */
-                usb_fill_bulk_urb(port->read_urb, port->serial->dev,
-                        usb_rcvbulkpipe(port->serial->dev,
-                                        port->bulk_in_endpointAddress),
-                        port->read_urb->transfer_buffer,
-                        port->read_urb->transfer_buffer_length,
-                        ftdi_read_bulk_callback, port);
+        dbg("%s - port %d", __func__, port->number);
 
-                result = usb_submit_urb(port->read_urb, GFP_ATOMIC);
-                if (result)
-                        dev_err(&port->dev,
-                                "%s - failed resubmitting read urb, error %d\n",
-                                __func__, result);
+        if (urb->status) {
+                dbg("%s - nonzero read bulk status received: %d",
+                                                __func__, urb->status);
+                return;
         }
-out:
-        tty_kref_put(tty);
-} /* ftdi_process_read */
 
+        usb_serial_debug_data(debug, &port->dev, __func__,
+                                urb->actual_length, urb->transfer_buffer);
+        ftdi_process_read(port);
+
+        spin_lock_irqsave(&port->lock, flags);
+        port->throttled = port->throttle_req;
+        if (!port->throttled) {
+                spin_unlock_irqrestore(&port->lock, flags);
+                ftdi_submit_read_urb(port, GFP_ATOMIC);
+        } else
+                spin_unlock_irqrestore(&port->lock, flags);
+}
 
 static void ftdi_break_ctl(struct tty_struct *tty, int break_state)
 {
@@ -2566,33 +2447,31 @@ static int ftdi_ioctl(struct tty_struct *tty, struct file *file,
 static void ftdi_throttle(struct tty_struct *tty)
 {
         struct usb_serial_port *port = tty->driver_data;
-        struct ftdi_private *priv = usb_get_serial_port_data(port);
         unsigned long flags;
 
         dbg("%s - port %d", __func__, port->number);
 
-        spin_lock_irqsave(&priv->rx_lock, flags);
-        priv->rx_flags |= THROTTLED;
-        spin_unlock_irqrestore(&priv->rx_lock, flags);
+        spin_lock_irqsave(&port->lock, flags);
+        port->throttle_req = 1;
+        spin_unlock_irqrestore(&port->lock, flags);
 }
 
-
-static void ftdi_unthrottle(struct tty_struct *tty)
+void ftdi_unthrottle(struct tty_struct *tty)
 {
         struct usb_serial_port *port = tty->driver_data;
-        struct ftdi_private *priv = usb_get_serial_port_data(port);
-        int actually_throttled;
+        int was_throttled;
         unsigned long flags;
 
         dbg("%s - port %d", __func__, port->number);
 
-        spin_lock_irqsave(&priv->rx_lock, flags);
-        actually_throttled = priv->rx_flags & ACTUALLY_THROTTLED;
-        priv->rx_flags &= ~(THROTTLED | ACTUALLY_THROTTLED);
-        spin_unlock_irqrestore(&priv->rx_lock, flags);
+        spin_lock_irqsave(&port->lock, flags);
+        was_throttled = port->throttled;
+        port->throttled = port->throttle_req = 0;
+        spin_unlock_irqrestore(&port->lock, flags);
 
-        if (actually_throttled)
-                schedule_delayed_work(&priv->rx_work, 0);
+        /* Resubmit urb if throttled and open. */
+        if (was_throttled && test_bit(ASYNCB_INITIALIZED, &port->port.flags))
+                ftdi_submit_read_urb(port, GFP_KERNEL);
 }
 
 static int __init ftdi_init(void)