diff options
author | Maciej W. Rozycki <macro@linux-mips.org> | 2008-07-24 00:29:49 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-07-24 13:47:29 -0400 |
commit | e9a8f4d1de12633bfb71b5fee47745b32877b7b5 (patch) | |
tree | 3bf0f747b32314491b9b6cf4f44a2c6d3288390e /drivers/serial | |
parent | 377135912806ddc87d56d64fafa685f4063c45f1 (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.c | 24 |
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 | */ | ||
650 | static 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 | |||
645 | static const char *dz_type(struct uart_port *uport) | 665 | static 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); |