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serial: turn serial console suspend a boot rather than compile time option 

Currently, there's a CONFIG_DISABLE_CONSOLE_SUSPEND that allows one to stop
the serial console from being suspended when the rest of the machine goes
to sleep.  This is incredibly useful for debugging power management-related
things; however, having it as a compile-time option has proved to be
incredibly inconvenient for us (OLPC).  There are plenty of times that we
want serial console to not suspend, but for the most part we'd like serial
console to be suspended.

This drops CONFIG_DISABLE_CONSOLE_SUSPEND, and replaces it with a kernel
boot parameter (no_console_suspend).  By default, the serial console will
be suspended along with the rest of the system; by passing
'no_console_suspend' to the kernel during boot, serial console will remain
alive during suspend.

For now, this is pretty serial console specific; further fixes could be
applied to make this work for things like netconsole.

Signed-off-by: Andres Salomon <dilinger@debian.org>
Acked-by: "Rafael J. Wysocki" <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Cc: Nigel Cunningham <nigel@suspend2.net>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andres Salomon 2007-10-18 03:04:50 -07:00 committed by Linus Torvalds
parent 438e2ce68d
commit 8f4ce8c32f
7 changed files with 32 additions and 27 deletions
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10
Documentation/kernel-parameters.txt
View File

@ -479,6 +479,16 @@ and is between 256 and 4096 characters. It is defined in the file
UART at the specified I/O port or MMIO address.
The options are the same as for ttyS, above.
no_console_suspend
[HW] Never suspend the console
Disable suspending of consoles during suspend and
hibernate operations. Once disabled, debugging
messages can reach various consoles while the rest
of the system is being put to sleep (ie, while
debugging driver suspend/resume hooks). This may
not work reliably with all consoles, but is known
to work with serial and VGA consoles.
cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Format:
<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]

4
Documentation/power/basic-pm-debugging.txt
View File

@ -78,8 +78,8 @@ c) Advanced debugging
In case the STD does not work on your system even in the minimal configuration
and compiling more drivers as modules is not practical or some modules cannot
be unloaded, you can use one of the more advanced debugging techniques to find
the problem. First, if there is a serial port in your box, you can set the
CONFIG_DISABLE_CONSOLE_SUSPEND kernel configuration option and try to log kernel
the problem. First, if there is a serial port in your box, you can boot the
kernel with the 'no_console_suspend' parameter and try to log kernel
messages using the serial console. This may provide you with some information
about the reasons of the suspend (resume) failure. Alternatively, it may be
possible to use a FireWire port for debugging with firescope

1
arch/powerpc/configs/pmac32_defconfig
View File

@ -209,7 +209,6 @@ CONFIG_PM=y
# CONFIG_PM_LEGACY is not set
CONFIG_PM_DEBUG=y
# CONFIG_PM_VERBOSE is not set
# CONFIG_DISABLE_CONSOLE_SUSPEND is not set
CONFIG_PM_SLEEP=y
CONFIG_SUSPEND=y
CONFIG_HIBERNATION=y

10
drivers/serial/serial_core.c
View File

@ -1959,12 +1959,11 @@ int uart_suspend_port(struct uart_driver *drv, struct uart_port *port)
mutex_lock(&state->mutex);
#ifdef CONFIG_DISABLE_CONSOLE_SUSPEND
if (uart_console(port)) {
if (!console_suspend_enabled && uart_console(port)) {
/* we're going to avoid suspending serial console */
mutex_unlock(&state->mutex);
return 0;
}
#endif
tty_dev = device_find_child(port->dev, &match, serial_match_port);
if (device_may_wakeup(tty_dev)) {
@ -2016,12 +2015,11 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *port)
mutex_lock(&state->mutex);
#ifdef CONFIG_DISABLE_CONSOLE_SUSPEND
if (uart_console(port)) {
if (!console_suspend_enabled && uart_console(port)) {
/* no need to resume serial console, it wasn't suspended */
mutex_unlock(&state->mutex);
return 0;
}
#endif
if (!port->suspended) {
disable_irq_wake(port->irq);

7
include/linux/console.h
View File

@ -122,14 +122,11 @@ extern void console_stop(struct console *);
extern void console_start(struct console *);
extern int is_console_locked(void);
#ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
extern int console_suspend_enabled;
/* Suspend and resume console messages over PM events */
extern void suspend_console(void);
extern void resume_console(void);
#else
static inline void suspend_console(void) {}
static inline void resume_console(void) {}
#endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */
int mda_console_init(void);
void prom_con_init(void);

11
kernel/power/Kconfig
View File

@ -44,17 +44,6 @@ config PM_VERBOSE
---help---
This option enables verbose messages from the Power Management code.
config DISABLE_CONSOLE_SUSPEND
bool "Keep console(s) enabled during suspend/resume (DANGEROUS)"
depends on PM_DEBUG && PM_SLEEP
default n
---help---
This option turns off the console suspend mechanism that prevents
debug messages from reaching the console during the suspend/resume
operations. This may be helpful when debugging device drivers'
suspend/resume routines, but may itself lead to problems, for example
if netconsole is used.
config PM_TRACE
bool "Suspend/resume event tracing"
depends on PM_DEBUG && X86 && PM_SLEEP && EXPERIMENTAL

16
kernel/printk.c
View File

@ -862,7 +862,16 @@ int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, cha
return -1;
}
#ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
int console_suspend_enabled = 1;
EXPORT_SYMBOL(console_suspend_enabled);
static int __init console_suspend_disable(char *str)
{
console_suspend_enabled = 0;
return 1;
}
__setup("no_console_suspend", console_suspend_disable);
/**
* suspend_console - suspend the console subsystem
*
@ -870,6 +879,8 @@ int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, cha
*/
void suspend_console(void)
{
if (!console_suspend_enabled)
return;
printk("Suspending console(s)\n");
acquire_console_sem();
console_suspended = 1;
@ -877,10 +888,11 @@ void suspend_console(void)
void resume_console(void)
{
if (!console_suspend_enabled)
return;
console_suspended = 0;
release_console_sem();
}
#endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */
/**
* acquire_console_sem - lock the console system for exclusive use.