tty: cyclades: drop broken alt-speed support

Setting an alt_speed using the ASYNC_SPD flags has been deprecated since
v2.1.69, and has been broken since v3.10 and commit 6865ff222cca ("TTY:
do not warn about setting speed via SPD_*") without anyone noticing.

Drop the broken alt-speed handling altogether, and add a ratelimited
warning about using TIOCCSERIAL to to change speed as being deprecated.

Note that using ASYNC_SPD_CUST is still supported.

Signed-off-by: Johan Hovold <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>
Reviewed-by: Alan Cox <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/cyclades.c

···
 	cflag = tty->termios.c_cflag;
 	iflag = tty->termios.c_iflag;
 
-	/*
-	 * Set up the tty->alt_speed kludge
-	 */
-	if ((info->port.flags & ASYNC_SPD_MASK) == ASYNC_SPD_HI)
-		tty->alt_speed = 57600;
-	if ((info->port.flags & ASYNC_SPD_MASK) == ASYNC_SPD_VHI)
-		tty->alt_speed = 115200;
-	if ((info->port.flags & ASYNC_SPD_MASK) == ASYNC_SPD_SHI)
-		tty->alt_speed = 230400;
-	if ((info->port.flags & ASYNC_SPD_MASK) == ASYNC_SPD_WARP)
-		tty->alt_speed = 460800;
-
 	card = info->card;
 	channel = info->line - card->first_line;
 
···
 		struct serial_struct __user *new_info)
 {
 	struct serial_struct new_serial;
+	int old_flags;
 	int ret;
 
 	if (copy_from_user(&new_serial, new_info, sizeof(new_serial)))
 		return -EFAULT;
 
 	mutex_lock(&info->port.mutex);
+
+	old_flags = info->port.flags;
+
 	if (!capable(CAP_SYS_ADMIN)) {
 		if (new_serial.close_delay != info->port.close_delay ||
 				new_serial.baud_base != info->baud ||
···
 
 check_and_exit:
 	if (tty_port_initialized(&info->port)) {
+		if ((new_serial.flags ^ old_flags) & ASYNC_SPD_MASK) {
+			/* warn about deprecation unless clearing */
+			if (new_serial.flags & ASYNC_SPD_MASK)
+				dev_warn_ratelimited(tty->dev, "use of SPD flags is deprecated\n");
+		}
 		cy_set_line_char(info, tty);
 		ret = 0;
 	} else {