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.

I have another version of this patch which keeps #ifdefs around; however,
it's uglier.  I prefer this version of the patch, and don't feel that it
increases bloat.  If people strongly disagree, let me know and I'll submit
the other patch.

Signed-off-by: Andres Salomon <dilinger@debian.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index af50f9bbe68e..4d5aae4da04f 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -469,6 +469,14 @@ and is between 256 and 4096 characters. It is defined in the file
 			switching to the matching ttyS device later.  The
 			options are the same as for ttyS, above.
 
+	no_console_suspend
+			[HW] Never suspend the serial console
+			Disable suspending the serial console during
+			suspend/resume operations.  If disabled, debugging
+			messages can reach the console while the rest of
+			the system is being put to sleep (ie, while
+			debugging driver suspend/resume hooks).
+
 	cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
 			Format:
 			<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]