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>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 98cf90f2631d736021478528fab34281a79b5659..189df0bcab99bfa1dfdeff83c1fd8d67a7fe83d3 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -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>]

diff --git a/Documentation/power/basic-pm-debugging.txt b/Documentation/power/basic-pm-debugging.txt
index 1a85e2b964dca0e34f4411cfef0098f6606c46b5..57aef2f6e0de6ad30673d8ce34a5430dc59ec5ab 100644 (file)
--- a/Documentation/power/basic-pm-debugging.txt
+++ b/Documentation/power/basic-pm-debugging.txt
@@ -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

diff --git a/arch/powerpc/configs/pmac32_defconfig b/arch/powerpc/configs/pmac32_defconfig
index 95b823b60c97ec9cd038f4bb45ffea8afdd6ec7a..8e5988c4a1646042d8516303828524b8b3ad45dc 100644 (file)
--- a/arch/powerpc/configs/pmac32_defconfig
+++ b/arch/powerpc/configs/pmac32_defconfig
@@ -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

diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index 68aa4da0186573fce0ed514f0d1ea0e784e864e5..103189095c80344ecadcdf15db3112abe8f947c1 100644 (file)
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -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);

diff --git a/include/linux/console.h b/include/linux/console.h
index 0a4542ddb73dab19ceb9477e22241dc3bc0fe33e..a5f88a6a259d84a92e93a905a7937b03b7501dbf 100644 (file)
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -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);

diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 14b0e10dc95c6a8a1b305f212e2300574120f16f..8e186c678149e23581969a7acfca814a00295b95 100644 (file)
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -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

diff --git a/kernel/printk.c b/kernel/printk.c
index 52493474f0abafdfd7939ab57f3f2d6ad2006695..a30fe33de395a7964f68e237c73de7344190b18a 100644 (file)
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -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.