USB: removal of tty->low_latency hack dating back to the old serial code

This removes tty->low_latency from all USB serial drivers that push
data into the tty layer at hard interrupt context. It's no longer needed
and actually harmful.

Signed-off-by: Oliver Neukum <oliver@neukum.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

18 files changed, 1 insertions, 111 deletions

diff --git a/drivers/usb/serial/cyberjack.c b/drivers/usb/serial/cyberjack.c
index 858bdd038fb..dd501bb63ed 100644
--- a/drivers/usb/serial/cyberjack.c
+++ b/drivers/usb/serial/cyberjack.c
@@ -175,13 +175,6 @@ static int  cyberjack_open(struct tty_struct *tty,
         dbg("%s - usb_clear_halt", __func__);
         usb_clear_halt(port->serial->dev, port->write_urb->pipe);
 
-        /* force low_latency on so that our tty_push actually forces
-         * the data through, otherwise it is scheduled, and with high
-         * data rates (like with OHCI) data can get lost.
-         */
-        if (tty)
-                tty->low_latency = 1;
-
         priv = usb_get_serial_port_data(port);
         spin_lock_irqsave(&priv->lock, flags);
         priv->rdtodo = 0;
diff --git a/drivers/usb/serial/cypress_m8.c b/drivers/usb/serial/cypress_m8.c
index eae4740d448..e568710b263 100644
--- a/drivers/usb/serial/cypress_m8.c
+++ b/drivers/usb/serial/cypress_m8.c
@@ -656,10 +656,6 @@ static int cypress_open(struct tty_struct *tty,
         priv->rx_flags = 0;
         spin_unlock_irqrestore(&priv->lock, flags);
 
-        /* setting to zero could cause data loss */
-        if (tty)
-                tty->low_latency = 1;
-
         /* raise both lines and set termios */
         spin_lock_irqsave(&priv->lock, flags);
         priv->line_control = CONTROL_DTR | CONTROL_RTS;
diff --git a/drivers/usb/serial/empeg.c b/drivers/usb/serial/empeg.c
index 8a69cce40b6..c709ec474a8 100644
--- a/drivers/usb/serial/empeg.c
+++ b/drivers/usb/serial/empeg.c
@@ -478,12 +478,6 @@ static void empeg_set_termios(struct tty_struct *tty,
         termios->c_cflag
                 |= CS8;         /* character size 8 bits */
 
-        /*
-         * Force low_latency on; otherwise the pushes are scheduled;
-         * this is bad as it opens up the possibility of dropping bytes
-         * on the floor.  We don't want to drop bytes on the floor. :)
-         */
-        tty->low_latency = 1;
         tty_encode_baud_rate(tty, 115200, 115200);
 }
 
diff --git a/drivers/usb/serial/garmin_gps.c b/drivers/usb/serial/garmin_gps.c
index a26a0e2cdb4..586d30ff450 100644
--- a/drivers/usb/serial/garmin_gps.c
+++ b/drivers/usb/serial/garmin_gps.c
@@ -973,14 +973,6 @@ static int garmin_open(struct tty_struct *tty,
 
         dbg("%s - port %d", __func__, port->number);
 
-        /*
-         * Force low_latency on so that our tty_push actually forces the data
-         * through, otherwise it is scheduled, and with high data rates (like
-         * with OHCI) data can get lost.
-         */
-        if (tty)
-                tty->low_latency = 1;
-
         spin_lock_irqsave(&garmin_data_p->lock, flags);
         garmin_data_p->mode  = initial_mode;
         garmin_data_p->count = 0;
diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
index 9d57cace373..4cec9906ccf 100644
--- a/drivers/usb/serial/generic.c
+++ b/drivers/usb/serial/generic.c
@@ -122,12 +122,6 @@ int usb_serial_generic_open(struct tty_struct *tty,
 
         dbg("%s - port %d", __func__, port->number);
 
-        /* force low_latency on so that our tty_push actually forces the data
-           through, otherwise it is scheduled, and with high data rates (like
-           with OHCI) data can get lost. */
-        if (tty)
-                tty->low_latency = 1;
-
         /* clear the throttle flags */
         spin_lock_irqsave(&port->lock, flags);
         port->throttled = 0;
diff --git a/drivers/usb/serial/io_edgeport.c b/drivers/usb/serial/io_edgeport.c
index e85c8c0d1ad..fb4a73d090f 100644
--- a/drivers/usb/serial/io_edgeport.c
+++ b/drivers/usb/serial/io_edgeport.c
@@ -193,8 +193,6 @@ static const struct divisor_table_entry divisor_table[] = {
 /* local variables */
 static int debug;
 
-static int low_latency = 1;     /* tty low latency flag, on by default */
-
 static atomic_t CmdUrbs;        /* Number of outstanding Command Write Urbs */
 
 
@@ -867,9 +865,6 @@ static int edge_open(struct tty_struct *tty,
         if (edge_port == NULL)
                 return -ENODEV;
 
-        if (tty)
-                tty->low_latency = low_latency;
-
         /* see if we've set up our endpoint info yet (can't set it up
            in edge_startup as the structures were not set up at that time.) */
         serial = port->serial;
@@ -3299,6 +3294,3 @@ MODULE_FIRMWARE("edgeport/down2.fw");
 
 module_param(debug, bool, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(debug, "Debug enabled or not");
-
-module_param(low_latency, bool, S_IRUGO | S_IWUSR);
-MODULE_PARM_DESC(low_latency, "Low latency enabled or not");
diff --git a/drivers/usb/serial/io_ti.c b/drivers/usb/serial/io_ti.c
index c3cdd00ddc4..513b25e044c 100644
--- a/drivers/usb/serial/io_ti.c
+++ b/drivers/usb/serial/io_ti.c
@@ -76,7 +76,6 @@ struct edgeport_uart_buf_desc {
 #define EDGE_READ_URB_STOPPING  1
 #define EDGE_READ_URB_STOPPED   2
 
-#define EDGE_LOW_LATENCY        1
 #define EDGE_CLOSING_WAIT       4000    /* in .01 sec */
 
 #define EDGE_OUT_BUF_SIZE       1024
@@ -232,7 +231,6 @@ static unsigned short OperationalBuildNumber;
 
 static int debug;
 
-static int low_latency = EDGE_LOW_LATENCY;
 static int closing_wait = EDGE_CLOSING_WAIT;
 static int ignore_cpu_rev;
 static int default_uart_mode;           /* RS232 */
@@ -1850,9 +1848,6 @@ static int edge_open(struct tty_struct *tty,
         if (edge_port == NULL)
                 return -ENODEV;
 
-        if (tty)
-                tty->low_latency = low_latency;
-
         port_number = port->number - port->serial->minor;
         switch (port_number) {
         case 0:
@@ -3008,9 +3003,6 @@ MODULE_FIRMWARE("edgeport/down3.bin");
 module_param(debug, bool, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(debug, "Debug enabled or not");
 
-module_param(low_latency, bool, S_IRUGO | S_IWUSR);
-MODULE_PARM_DESC(low_latency, "Low latency enabled or not");
-
 module_param(closing_wait, int, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(closing_wait, "Maximum wait for data to drain, in .01 secs");
 
diff --git a/drivers/usb/serial/ipaq.c b/drivers/usb/serial/ipaq.c
index ef92095b073..cd62825a9ac 100644
--- a/drivers/usb/serial/ipaq.c
+++ b/drivers/usb/serial/ipaq.c
@@ -631,13 +631,7 @@ static int ipaq_open(struct tty_struct *tty,
                 priv->free_len += PACKET_SIZE;
         }
 
-        /*
-         * Force low latency on. This will immediately push data to the line
-         * discipline instead of queueing.
-         */
-
         if (tty) {
-                tty->low_latency = 1;
                 /* FIXME: These two are bogus */
                 tty->raw = 1;
                 tty->real_raw = 1;
diff --git a/drivers/usb/serial/ipw.c b/drivers/usb/serial/ipw.c
index f530032ed93..da2a2b46644 100644
--- a/drivers/usb/serial/ipw.c
+++ b/drivers/usb/serial/ipw.c
@@ -207,9 +207,6 @@ static int ipw_open(struct tty_struct *tty,
         if (!buf_flow_init)
                 return -ENOMEM;
 
-        if (tty)
-                tty->low_latency = 1;
-
         /* --1: Tell the modem to initialize (we think) From sniffs this is
          *      always the first thing that gets sent to the modem during
          *      opening of the device */
diff --git a/drivers/usb/serial/iuu_phoenix.c b/drivers/usb/serial/iuu_phoenix.c
index 2314c6ae4fc..4473d442b2a 100644
--- a/drivers/usb/serial/iuu_phoenix.c
+++ b/drivers/usb/serial/iuu_phoenix.c
@@ -1051,7 +1051,6 @@ static int iuu_open(struct tty_struct *tty,
                 tty->termios->c_oflag = 0;
                 tty->termios->c_iflag = 0;
                 priv->termios_initialized = 1;
-                tty->low_latency = 1;
                 priv->poll = 0;
          }
         spin_unlock_irqrestore(&priv->lock, flags);
diff --git a/drivers/usb/serial/kobil_sct.c b/drivers/usb/serial/kobil_sct.c
index 6286baad939..c148544953b 100644
--- a/drivers/usb/serial/kobil_sct.c
+++ b/drivers/usb/serial/kobil_sct.c
@@ -231,13 +231,7 @@ static int kobil_open(struct tty_struct *tty,
         /* someone sets the dev to 0 if the close method has been called */
         port->interrupt_in_urb->dev = port->serial->dev;
 
-
-        /* force low_latency on so that our tty_push actually forces
-         * the data through, otherwise it is scheduled, and with high
-         * data rates (like with OHCI) data can get lost.
-         */
         if (tty) {
-                tty->low_latency = 1;
 
                 /* Default to echo off and other sane device settings */
                 tty->termios->c_lflag = 0;
diff --git a/drivers/usb/serial/mos7720.c b/drivers/usb/serial/mos7720.c
index e772cc0a97f..24e3b5d4b4d 100644
--- a/drivers/usb/serial/mos7720.c
+++ b/drivers/usb/serial/mos7720.c
@@ -446,13 +446,6 @@ static int mos7720_open(struct tty_struct *tty,
         data = 0x0c;
         send_mos_cmd(serial, MOS_WRITE, port_number, 0x01, &data);
 
-        /* force low_latency on so that our tty_push actually forces *
-         * the data through,otherwise it is scheduled, and with      *
-         * high data rates (like with OHCI) data can get lost.       */
-
-        if (tty)
-                tty->low_latency = 1;
-
         /* see if we've set up our endpoint info yet   *
          * (can't set it up in mos7720_startup as the  *
          * structures were not set up at that time.)   */
diff --git a/drivers/usb/serial/mos7840.c b/drivers/usb/serial/mos7840.c
index 499b7b82a0e..84fb1dcd30d 100644
--- a/drivers/usb/serial/mos7840.c
+++ b/drivers/usb/serial/mos7840.c
@@ -1007,12 +1007,6 @@ static int mos7840_open(struct tty_struct *tty,
         status = mos7840_set_reg_sync(port, mos7840_port->ControlRegOffset,
                                                                         Data);
 
-        /* force low_latency on so that our tty_push actually forces *
-         * the data through,otherwise it is scheduled, and with      *
-         * high data rates (like with OHCI) data can get lost.       */
-        if (tty)
-                tty->low_latency = 1;
-
         /* Check to see if we've set up our endpoint info yet    *
          * (can't set it up in mos7840_startup as the structures *
          * were not set up at that time.)                        */
diff --git a/drivers/usb/serial/opticon.c b/drivers/usb/serial/opticon.c
index 839583dc8b6..b500ad10b75 100644
--- a/drivers/usb/serial/opticon.c
+++ b/drivers/usb/serial/opticon.c
@@ -159,14 +159,6 @@ static int opticon_open(struct tty_struct *tty, struct usb_serial_port *port,
         priv->port = port;
         spin_unlock_irqrestore(&priv->lock, flags);
 
-        /*
-         * Force low_latency on so that our tty_push actually forces the data
-         * through, otherwise it is scheduled, and with high data rates (like
-         * with OHCI) data can get lost.
-         */
-        if (tty)
-                tty->low_latency = 1;
-
         /* Start reading from the device */
         usb_fill_bulk_urb(priv->bulk_read_urb, priv->udev,
                           usb_rcvbulkpipe(priv->udev,
diff --git a/drivers/usb/serial/option.c b/drivers/usb/serial/option.c
index 47bd070f24b..7817b82889c 100644
--- a/drivers/usb/serial/option.c
+++ b/drivers/usb/serial/option.c
@@ -936,9 +936,6 @@ static int option_open(struct tty_struct *tty,
                                 usb_pipeout(urb->pipe), 0); */
         }
 
-        if (tty)
-                tty->low_latency = 1;
-
         option_send_setup(tty, port);
 
         return 0;
diff --git a/drivers/usb/serial/sierra.c b/drivers/usb/serial/sierra.c
index 7da3775a097..913225c6161 100644
--- a/drivers/usb/serial/sierra.c
+++ b/drivers/usb/serial/sierra.c
@@ -598,9 +598,6 @@ static int sierra_open(struct tty_struct *tty,
                 }
         }
 
-        if (tty)
-                tty->low_latency = 1;
-
         sierra_send_setup(tty, port);
 
         /* start up the interrupt endpoint if we have one */
diff --git a/drivers/usb/serial/ti_usb_3410_5052.c b/drivers/usb/serial/ti_usb_3410_5052.c
index 9c4c700c7cc..0a64bac306e 100644
--- a/drivers/usb/serial/ti_usb_3410_5052.c
+++ b/drivers/usb/serial/ti_usb_3410_5052.c
@@ -50,11 +50,10 @@
 
 #define TI_TRANSFER_TIMEOUT     2
 
-#define TI_DEFAULT_LOW_LATENCY  0
 #define TI_DEFAULT_CLOSING_WAIT 4000            /* in .01 secs */
 
 /* supported setserial flags */
-#define TI_SET_SERIAL_FLAGS     (ASYNC_LOW_LATENCY)
+#define TI_SET_SERIAL_FLAGS     0
 
 /* read urb states */
 #define TI_READ_URB_RUNNING     0
@@ -161,7 +160,6 @@ static int ti_buf_get(struct circ_buf *cb, char *buf, int count);
 
 /* module parameters */
 static int debug;
-static int low_latency = TI_DEFAULT_LOW_LATENCY;
 static int closing_wait = TI_DEFAULT_CLOSING_WAIT;
 static ushort vendor_3410[TI_EXTRA_VID_PID_COUNT];
 static unsigned int vendor_3410_count;
@@ -296,10 +294,6 @@ MODULE_FIRMWARE("mts_edge.fw");
 module_param(debug, bool, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(debug, "Enable debugging, 0=no, 1=yes");
 
-module_param(low_latency, bool, S_IRUGO | S_IWUSR);
-MODULE_PARM_DESC(low_latency,
-                "TTY low_latency flag, 0=off, 1=on, default is off");
-
 module_param(closing_wait, int, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(closing_wait,
     "Maximum wait for data to drain in close, in .01 secs, default is 4000");
@@ -448,7 +442,6 @@ static int ti_startup(struct usb_serial *serial)
                 spin_lock_init(&tport->tp_lock);
                 tport->tp_uart_base_addr = (i == 0 ?
                                 TI_UART1_BASE_ADDR : TI_UART2_BASE_ADDR);
-                tport->tp_flags = low_latency ? ASYNC_LOW_LATENCY : 0;
                 tport->tp_closing_wait = closing_wait;
                 init_waitqueue_head(&tport->tp_msr_wait);
                 init_waitqueue_head(&tport->tp_write_wait);
@@ -528,10 +521,6 @@ static int ti_open(struct tty_struct *tty,
         if (mutex_lock_interruptible(&tdev->td_open_close_lock))
                 return -ERESTARTSYS;
 
-        if (tty)
-                tty->low_latency =
-                                (tport->tp_flags & ASYNC_LOW_LATENCY) ? 1 : 0;
-
         port_number = port->number - port->serial->minor;
 
         memset(&(tport->tp_icount), 0x00, sizeof(tport->tp_icount));
@@ -1454,7 +1443,6 @@ static int ti_set_serial_info(struct tty_struct *tty, struct ti_port *tport,
                 return -EFAULT;
 
         tport->tp_flags = new_serial.flags & TI_SET_SERIAL_FLAGS;
-        tty->low_latency = (tport->tp_flags & ASYNC_LOW_LATENCY) ? 1 : 0;
         tport->tp_closing_wait = new_serial.closing_wait;
 
         return 0;
diff --git a/drivers/usb/serial/visor.c b/drivers/usb/serial/visor.c
index 4facce3d936..5ac414bda71 100644
--- a/drivers/usb/serial/visor.c
+++ b/drivers/usb/serial/visor.c
@@ -296,14 +296,6 @@ static int visor_open(struct tty_struct *tty, struct usb_serial_port *port,
         priv->throttled = 0;
         spin_unlock_irqrestore(&priv->lock, flags);
 
-        /*
-         * Force low_latency on so that our tty_push actually forces the data
-         * through, otherwise it is scheduled, and with high data rates (like
-         * with OHCI) data can get lost.
-         */
-        if (tty)
-                tty->low_latency = 1;
-
         /* Start reading from the device */
         usb_fill_bulk_urb(port->read_urb, serial->dev,
                            usb_rcvbulkpipe(serial->dev,