pm: boot time suspend selftest

Boot-time test for system suspend states (STR or standby).  The generic
RTC framework triggers wakeup alarms, which are used to exit those states.

  - Measures some aspects of suspend time ... this uses "jiffies" until
    someone converts it to use a timebase that works properly even while
    timer IRQs are disabled.

  - Triggered by a command line parameter.  By default nothing even
    vaguely troublesome will happen, but "test_suspend=mem" will give
    you a brief STR test during system boot.  (Or you may need to use
    "test_suspend=standby" instead, if your hardware needs that.)

This isn't without problems.  It fires early enough during boot that for
example both PCMCIA and MMC stacks have misbehaved.  The workaround in
those cases was to boot without such media cards inserted.

[matthltc@us.ibm.com: fix compile failure in boot time suspend selftest]
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Pavel Machek <pavel@suse.cz>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 1 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 01a2992b5754..4d705713cabc 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -87,7 +87,8 @@ parameter is applicable:
         SH      SuperH architecture is enabled.
         SMP     The kernel is an SMP kernel.
         SPARC   Sparc architecture is enabled.
-        SWSUSP  Software suspend is enabled.
+        SWSUSP  Software suspend (hibernation) is enabled.
+        SUSPEND System suspend states are enabled.
         TS      Appropriate touchscreen support is enabled.
         USB     USB support is enabled.
         USBHID  USB Human Interface Device support is enabled.
@@ -2123,6 +2124,12 @@ and is between 256 and 4096 characters. It is defined in the file
 
         tdfx=           [HW,DRM]
 
+        test_suspend=   [SUSPEND]
+                        Specify "mem" (for Suspend-to-RAM) or "standby" (for
+                        standby suspend) as the system sleep state to briefly
+                        enter during system startup.  The system is woken from
+                        this state using a wakeup-capable RTC alarm.
+
         thash_entries=  [KNL,NET]
                         Set number of hash buckets for TCP connection