kernel/serial-460800.patch

Bugzilla: N/A
Upstream-status: Fedora mustard but I have no idea why.


diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 1d42dba6121d..30a5fde26949 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -5,6 +5,9 @@
  *
  *  Copyright (C) 2001 Russell King.
  *
+ *  2005/09/16: Enabled higher baud rates for 16C95x.
+ *		(Mathias Adam <a2@adamis.de>)
+ *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
@@ -2246,6 +2249,14 @@ static unsigned int serial8250_get_divisor(struct uart_port *port, unsigned int
 	else if ((port->flags & UPF_MAGIC_MULTIPLIER) &&
 		 baud == (port->uartclk/8))
 		quot = 0x8002;
+	/*
+	 * For 16C950s UART_TCR is used in combination with divisor==1
+	 * to achieve baud rates up to baud_base*4.
+	 */
+	else if ((port->type == PORT_16C950) &&
+		 baud > (port->uartclk/16))
+		quot = 1;
+
 	else
 		quot = uart_get_divisor(port, baud);
 
@@ -2259,7 +2270,7 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
 	struct uart_8250_port *up = up_to_u8250p(port);
 	unsigned char cval;
 	unsigned long flags;
-	unsigned int baud, quot;
+	unsigned int baud, quot, max_baud;
 
 	switch (termios->c_cflag & CSIZE) {
 	case CS5:
@@ -2294,9 +2305,10 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
 	/*
 	 * Ask the core to calculate the divisor for us.
 	 */
+	max_baud = (up->port.type == PORT_16C950 ? port->uartclk/4 : port->uartclk/16);
 	baud = uart_get_baud_rate(port, termios, old,
 				  port->uartclk / 16 / 0xffff,
-				  port->uartclk / 16);
+				  max_baud);
 	quot = serial8250_get_divisor(port, baud);
 
 	/*
@@ -2336,6 +2348,19 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
 	spin_lock_irqsave(&port->lock, flags);
 
 	/*
+	 * 16C950 supports additional prescaler ratios between 1:16 and 1:4
+	 * thus increasing max baud rate to uartclk/4.
+	 */
+	if (up->port.type == PORT_16C950) {
+		if (baud == port->uartclk/4)
+			serial_icr_write(up, UART_TCR, 0x4);
+		else if (baud == port->uartclk/8)
+			serial_icr_write(up, UART_TCR, 0x8);
+		else
+			serial_icr_write(up, UART_TCR, 0);
+	}
+
+	/*
 	 * Update the per-port timeout.
 	 */
 	uart_update_timeout(port, termios->c_cflag, baud);