75 lines
2.4 KiB
Diff
75 lines
2.4 KiB
Diff
Bugzilla: N/A
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Upstream-status: Fedora mustard but I have no idea why.
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diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
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index 1d42dba6121d..30a5fde26949 100644
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--- a/drivers/tty/serial/8250/8250_core.c
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+++ b/drivers/tty/serial/8250/8250_core.c
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@@ -5,6 +5,9 @@
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*
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* Copyright (C) 2001 Russell King.
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*
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+ * 2005/09/16: Enabled higher baud rates for 16C95x.
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+ * (Mathias Adam <a2@adamis.de>)
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+ *
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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@@ -2246,6 +2249,14 @@ static unsigned int serial8250_get_divisor(struct uart_port *port, unsigned int
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else if ((port->flags & UPF_MAGIC_MULTIPLIER) &&
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baud == (port->uartclk/8))
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quot = 0x8002;
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+ /*
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+ * For 16C950s UART_TCR is used in combination with divisor==1
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+ * to achieve baud rates up to baud_base*4.
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+ */
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+ else if ((port->type == PORT_16C950) &&
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+ baud > (port->uartclk/16))
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+ quot = 1;
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+
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else
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quot = uart_get_divisor(port, baud);
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@@ -2259,7 +2270,7 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
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struct uart_8250_port *up = up_to_u8250p(port);
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unsigned char cval;
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unsigned long flags;
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- unsigned int baud, quot;
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+ unsigned int baud, quot, max_baud;
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switch (termios->c_cflag & CSIZE) {
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case CS5:
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@@ -2294,9 +2305,10 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
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/*
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* Ask the core to calculate the divisor for us.
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*/
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+ max_baud = (up->port.type == PORT_16C950 ? port->uartclk/4 : port->uartclk/16);
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baud = uart_get_baud_rate(port, termios, old,
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port->uartclk / 16 / 0xffff,
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- port->uartclk / 16);
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+ max_baud);
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quot = serial8250_get_divisor(port, baud);
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/*
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@@ -2336,6 +2348,19 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
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spin_lock_irqsave(&port->lock, flags);
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/*
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+ * 16C950 supports additional prescaler ratios between 1:16 and 1:4
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+ * thus increasing max baud rate to uartclk/4.
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+ */
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+ if (up->port.type == PORT_16C950) {
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+ if (baud == port->uartclk/4)
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+ serial_icr_write(up, UART_TCR, 0x4);
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+ else if (baud == port->uartclk/8)
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+ serial_icr_write(up, UART_TCR, 0x8);
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+ else
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+ serial_icr_write(up, UART_TCR, 0);
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+ }
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+
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+ /*
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* Update the per-port timeout.
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*/
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uart_update_timeout(port, termios->c_cflag, baud);
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