printk: add console_suspend module parameter

We are enabling some power features on medfield.  To test suspend-2-RAM
conveniently, we need turn on/off console_suspend_enabled frequently.

Add a module parameter, so users could change it by:
/sys/module/printk/parameters/console_suspend

Signed-off-by: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 9 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 106efe1e2ba..c2efe285396 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1669,6 +1669,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         debugging driver suspend/resume hooks).  This may
                         not work reliably with all consoles, but is known
                         to work with serial and VGA consoles.
+                        To facilitate more flexible debugging, we also add
+                        console_suspend, a printk module parameter to control
+                        it. Users could use console_suspend (usually
+                        /sys/module/printk/parameters/console_suspend) to
+                        turn on/off it dynamically.
 
         noaliencache    [MM, NUMA, SLAB] Disables the allocation of alien
                         caches in the slab allocator.  Saves per-node memory,
diff --git a/kernel/printk.c b/kernel/printk.c
index e62f949ec14..6d9dedd1145 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1111,6 +1111,10 @@ static int __init console_suspend_disable(char *str)
         return 1;
 }
 __setup("no_console_suspend", console_suspend_disable);
+module_param_named(console_suspend, console_suspend_enabled,
+                bool, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
+        " and hibernate operations");
 
 /**
  * suspend_console - suspend the console subsystem