[PATCH] printk/of_serial: fix serial console cessation part way through boot.
schivers at csc.com
Wed May 14 08:04:39 EST 2014
"serial_core: Unregister console in uart_remove_one_port()"
fixed a crash where a serial port was removed but
not deregistered as a console.
There is a side effect of that commit for platforms having serial consoles
and of_serial configured (CONFIG_SERIAL_OF_PLATFORM). The serial console
is disabled midway through the boot process.
This cessation of the serial console affects PowerPC computers
such as the MVME5100 and SAM440EP.
The sequence is:
bootconsole [udbg0] enabled
serial8250/16550 driver initialises and registers its UARTS,
one of these is the serial console.
console [ttyS0] enabled
of_serial probes "platform" devices, registering them as it goes.
One of these is the serial console.
console [ttyS0] disabled.
The disabling of the serial console is due to:
a. unregister_console in printk not clearing the
CONS_ENABLED bit in the console flags,
even though it has announced that the console is disabled; and
b. of_platform_serial_probe in of_serial not setting the port type
before it registers with serial8250_register_8250_port.
This patch ensures that the serial console is re-enabled when of_serial
registers a serial port that corresponds to the designated console.
Signed-off-by: Stephen Chivers <schivers at csc.com>
Tested-by: Stephen Chivers <schivers at csc.com>
Acked-by: Geert Uytterhoeven <geert at linux-m68k.org> [unregister_console]
The above failure was identified in Linux-3.15-rc2.
Tested using MVME5100 and SAM440EP PowerPC computers with
kernels built from Linux-3.15-rc5 and tty-next.
The continued operation of the serial console is vital for computers
such as the MVME5100 as that Single Board Computer does not
have any grapical/display hardware.
drivers/tty/serial/of_serial.c | 1 +
kernel/printk/printk.c | 1 +
2 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/drivers/tty/serial/of_serial.c b/drivers/tty/serial/of_serial.c
index 9924660..27981e2 100644
@@ -173,6 +173,7 @@ static int of_platform_serial_probe(struct platform_device *ofdev)
struct uart_8250_port port8250;
memset(&port8250, 0, sizeof(port8250));
+ port.type = port_type;
port8250.port = port;
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 7228258..221229c 100644
@@ -2413,6 +2413,7 @@ int unregister_console(struct console *console)
if (console_drivers != NULL && console->flags & CON_CONSDEV)
console_drivers->flags |= CON_CONSDEV;
+ console->flags &= ~CON_ENABLED;
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