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authorMaciej W. Rozycki <macro@linux-mips.org>2008-07-24 00:29:49 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-24 13:47:29 -0400
commite9a8f4d1de12633bfb71b5fee47745b32877b7b5 (patch)
tree3bf0f747b32314491b9b6cf4f44a2c6d3288390e /drivers/serial
parent377135912806ddc87d56d64fafa685f4063c45f1 (diff)
serial: DZ11: avoid a hang at console switch-over
Changes to the generic console support code that happened a while ago introduced a scenario where the initial console is used in parallel with the final console during a brief period when switching between the two is in progress. During that time a message about the switch-over is printed. With some combinations of chips, firmware and drivers, such as the DEC DZ11 clone used with the DECstation, a hang may happen because the firmware used for the initial console may not expect the state of the chip after it has been initialised by the driver. This is a workaround for the DZ11 which reuses the power-management callback to keep the transmitter of the line associated with the console enabled. It reflects the consensus reached in a discussion a while ago. Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org> Cc: Jiri Slaby <jirislaby@gmail.com> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/serial')
-rw-r--r--drivers/serial/dz.c24
1 files changed, 24 insertions, 0 deletions
diff --git a/drivers/serial/dz.c b/drivers/serial/dz.c
index a81d2c2ff8a2..6042b87797a1 100644
--- a/drivers/serial/dz.c
+++ b/drivers/serial/dz.c
@@ -642,6 +642,26 @@ static void dz_set_termios(struct uart_port *uport, struct ktermios *termios,
642 spin_unlock_irqrestore(&dport->port.lock, flags); 642 spin_unlock_irqrestore(&dport->port.lock, flags);
643} 643}
644 644
645/*
646 * Hack alert!
647 * Required solely so that the initial PROM-based console
648 * works undisturbed in parallel with this one.
649 */
650static void dz_pm(struct uart_port *uport, unsigned int state,
651 unsigned int oldstate)
652{
653 struct dz_port *dport = to_dport(uport);
654 unsigned long flags;
655
656 spin_lock_irqsave(&dport->port.lock, flags);
657 if (state < 3)
658 dz_start_tx(&dport->port);
659 else
660 dz_stop_tx(&dport->port);
661 spin_unlock_irqrestore(&dport->port.lock, flags);
662}
663
664
645static const char *dz_type(struct uart_port *uport) 665static const char *dz_type(struct uart_port *uport)
646{ 666{
647 return "DZ"; 667 return "DZ";
@@ -738,6 +758,7 @@ static struct uart_ops dz_ops = {
738 .startup = dz_startup, 758 .startup = dz_startup,
739 .shutdown = dz_shutdown, 759 .shutdown = dz_shutdown,
740 .set_termios = dz_set_termios, 760 .set_termios = dz_set_termios,
761 .pm = dz_pm,
741 .type = dz_type, 762 .type = dz_type,
742 .release_port = dz_release_port, 763 .release_port = dz_release_port,
743 .request_port = dz_request_port, 764 .request_port = dz_request_port,
@@ -861,7 +882,10 @@ static int __init dz_console_setup(struct console *co, char *options)
861 if (ret) 882 if (ret)
862 return ret; 883 return ret;
863 884
885 spin_lock_init(&dport->port.lock); /* For dz_pm(). */
886
864 dz_reset(dport); 887 dz_reset(dport);
888 dz_pm(uport, 0, -1);
865 889
866 if (options) 890 if (options)
867 uart_parse_options(options, &baud, &parity, &bits, &flow); 891 uart_parse_options(options, &baud, &parity, &bits, &flow);