cypress_m8: use appropriate URB polling interval

The polling interval for the device can't always be 1msec.  If it is
too quick, the device can fail causing a fatal (to the driver) EILSEQ
error from the USB core.  The actual correct value is reported by the
device as part of its configuration data, so use that value as the
default.  On a DeLorme Earthmate for example, the device reports that
it wants a 6msec interval.  As part of this fix, the "interval" module
option has been fixed as well; the device's default can be overridden
by specifying interval=<value> as a module option.
Signed-off-by: NMike Isely <isely@pobox.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/cypress_m8.c

@@ -129,6 +129,8 @@ struct cypress_private {
 	int cmd_ctrl;			   /* always set this to 1 before issuing a command */
 	struct cypress_buf *buf;	   /* write buffer */
 	int write_urb_in_use;		   /* write urb in use indicator */
+	int write_urb_interval;            /* interval to use for write urb */
+	int read_urb_interval;             /* interval to use for read urb */
 	int termios_initialized;
 	__u8 line_control;	   	   /* holds dtr / rts value */
 	__u8 current_status;	   	   /* received from last read - info on dsr,cts,cd,ri,etc */
@@ -472,8 +474,9 @@ static unsigned rate_to_mask (int rate)
 static int generic_startup (struct usb_serial *serial)
 {
 	struct cypress_private *priv;
+	struct usb_serial_port *port = serial->port[0];
 
-	dbg("%s - port %d", __FUNCTION__, serial->port[0]->number);
+	dbg("%s - port %d", __FUNCTION__, port->number);
 
 	priv = kzalloc(sizeof (struct cypress_private), GFP_KERNEL);
 	if (!priv)
@@ -489,13 +492,24 @@ static int generic_startup (struct usb_serial *serial)
 	
 	usb_reset_configuration (serial->dev);
 	
-	interval = 1;
 	priv->cmd_ctrl = 0;
 	priv->line_control = 0;
 	priv->termios_initialized = 0;
 	priv->rx_flags = 0;
 	priv->cbr_mask = B300;
-	usb_set_serial_port_data(serial->port[0], priv);
+	if (interval > 0) {
+		priv->write_urb_interval = interval;
+		priv->read_urb_interval = interval;
+		dbg("%s - port %d read & write intervals forced to %d",
+		    __FUNCTION__,port->number,interval);
+	} else {
+		priv->write_urb_interval = port->interrupt_out_urb->interval;
+		priv->read_urb_interval = port->interrupt_in_urb->interval;
+		dbg("%s - port %d intervals: read=%d write=%d",
+		    __FUNCTION__,port->number,
+		    priv->read_urb_interval,priv->write_urb_interval);
+	}
+	usb_set_serial_port_data(port, priv);
 	
 	return 0;
 }
@@ -624,7 +638,7 @@ static int cypress_open (struct usb_serial_port *port, struct file *filp)
 	usb_fill_int_urb(port->interrupt_in_urb, serial->dev,
 		usb_rcvintpipe(serial->dev, port->interrupt_in_endpointAddress),
 		port->interrupt_in_urb->transfer_buffer, port->interrupt_in_urb->transfer_buffer_length,
-		cypress_read_int_callback, port, interval);
+		cypress_read_int_callback, port, priv->read_urb_interval);
 	result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
 
 	if (result){
@@ -808,7 +822,7 @@ static void cypress_send(struct usb_serial_port *port)
 
 	port->interrupt_out_urb->transfer_buffer_length = actual_size;
 	port->interrupt_out_urb->dev = port->serial->dev;
-	port->interrupt_out_urb->interval = interval;
+	port->interrupt_out_urb->interval = priv->write_urb_interval;
 	result = usb_submit_urb (port->interrupt_out_urb, GFP_ATOMIC);
 	if (result) {
 		dev_err(&port->dev, "%s - failed submitting write urb, error %d\n", __FUNCTION__,
@@ -1349,7 +1363,7 @@ static void cypress_read_int_callback(struct urb *urb, struct pt_regs *regs)
 					port->interrupt_in_endpointAddress),
 				port->interrupt_in_urb->transfer_buffer,
 				port->interrupt_in_urb->transfer_buffer_length,
-				cypress_read_int_callback, port, interval);
+				cypress_read_int_callback, port, priv->read_urb_interval);
 		result = usb_submit_urb(port->interrupt_in_urb, GFP_ATOMIC);
 		if (result)
 			dev_err(&urb->dev->dev, "%s - failed resubmitting "