PM / sleep: System sleep state selection interface rework

There are systems in which the platform doesn't support any special
sleep states, so suspend-to-idle (PM_SUSPEND_FREEZE) is the only
available system sleep state.  However, some user space frameworks
only use the "mem" and (sometimes) "standby" sleep state labels, so
the users of those systems need to modify user space in order to be
able to use system suspend at all and that may be a pain in practice.

Commit 0399d4db3edf (PM / sleep: Introduce command line argument for
sleep state enumeration) attempted to address this problem by adding
a command line argument to change the meaning of the "mem" string in
/sys/power/state to make it trigger suspend-to-idle (instead of
suspend-to-RAM).

However, there also are systems in which the platform does support
special sleep states, but suspend-to-idle is the preferred one anyway
(it even may save more energy than the platform-provided sleep states
in some cases) and the above commit doesn't help in those cases.

For this reason, rework the system sleep state selection interface
again (but preserve backwards compatibiliby).  Namely, add a new
sysfs file, /sys/power/mem_sleep, that will control the system
suspend mode triggered by writing "mem" to /sys/power/state (in
analogy with what /sys/power/disk does for hibernation).  Make it
select suspend-to-RAM ("deep" sleep) by default (if supported) and
fall back to suspend-to-idle ("s2idle") otherwise and add a new
command line argument, mem_sleep_default, allowing that default to
be overridden if need be.

At the same time, drop the relative_sleep_states command line
argument that doesn't make sense any more.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mario Limonciello <mario.limonciello@dell.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/kernel/power/power.h b/kernel/power/power.h
index 56d1d0dedf76..1dfa0da827d3 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -189,11 +189,15 @@ extern void swsusp_show_speed(ktime_t, ktime_t, unsigned int, char *);
 
 #ifdef CONFIG_SUSPEND
 /* kernel/power/suspend.c */
-extern const char *pm_labels[];
+extern const char * const pm_labels[];
 extern const char *pm_states[];
+extern const char *mem_sleep_states[];
+extern suspend_state_t mem_sleep_current;
 
 extern int suspend_devices_and_enter(suspend_state_t state);
 #else /* !CONFIG_SUSPEND */
+#define mem_sleep_current	PM_SUSPEND_ON
+
 static inline int suspend_devices_and_enter(suspend_state_t state)
 {
 	return -ENOSYS;