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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);
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