diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c index 2209620..659c1bb 100644 --- a/drivers/tty/serial/8250/8250.c +++ b/drivers/tty/serial/8250/8250.c @@ -7,6 +7,9 @@ * * Copyright (C) 2001 Russell King. * + * 2005/09/16: Enabled higher baud rates for 16C95x. + * (Mathias Adam ) + * * 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 @@ -2227,6 +2230,14 @@ 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); @@ -2240,7 +2251,7 @@ serial8250_set_termios(struct uart_port *port, struct ktermios *termios, container_of(port, struct uart_8250_port, port); unsigned char cval, fcr = 0; unsigned long flags; - unsigned int baud, quot; + unsigned int baud, quot, max_baud; int fifo_bug = 0; switch (termios->c_cflag & CSIZE) { @@ -2272,9 +2283,10 @@ serial8250_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); /* @@ -2311,6 +2323,19 @@ serial8250_set_termios(struct uart_port *port, struct ktermios *termios, spin_lock_irqsave(&up->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);