[RFC PATCH v1 1/2] cpuidle: allow idle state to be found as deepest state for s2idle only

[zhang . lyra]

From: Chunyan Zhang <chunyan.zhang@xxxxxxxxxx>

Add a new flag CPUIDLE_FLAG_S2IDLE to allow c-state to be found as
deepest state for s2idle only, so that users can add a new c-state
for using s2idle and don't worry disturbing other use cases such as
play_idle() which probably don't want to enter into so much deep
idle state since devices are not suspended for that kind of cases.

Signed-off-by: Chunyan Zhang <chunyan.zhang@xxxxxxxxxx>
---
 drivers/cpuidle/cpuidle.c        | 3 ++-
 drivers/cpuidle/dt_idle_states.c | 3 +++
 include/linux/cpuidle.h          | 1 +
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index de81298051b3..bb61f0c271d2 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -89,7 +89,8 @@ static int find_deepest_state(struct cpuidle_driver *drv,
 		    s->exit_latency_ns <= latency_req ||
 		    s->exit_latency_ns > max_latency_ns ||
 		    (s->flags & forbidden_flags) ||
-		    (s2idle && !s->enter_s2idle))
+		    (s2idle && !s->enter_s2idle) ||
+		    (!s2idle && (s->flags & CPUIDLE_FLAG_S2ILDE)))
 			continue;
 
 		latency_req = s->exit_latency_ns;
diff --git a/drivers/cpuidle/dt_idle_states.c b/drivers/cpuidle/dt_idle_states.c
index 252f2a9686a6..530db2726c05 100644
--- a/drivers/cpuidle/dt_idle_states.c
+++ b/drivers/cpuidle/dt_idle_states.c
@@ -80,6 +80,9 @@ static int init_state_node(struct cpuidle_state *idle_state,
 	idle_state->flags = 0;
 	if (of_property_read_bool(state_node, "local-timer-stop"))
 		idle_state->flags |= CPUIDLE_FLAG_TIMER_STOP;
+
+	if (of_property_read_bool(state_node, "for-s2idle-only"))
+		idle_state->flags |= CPUIDLE_FLAG_S2ILDE;
 	/*
 	 * TODO:
 	 *	replace with kstrdup and pointer assignment when name
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index ec2ef63771f0..08da701f74cd 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -78,6 +78,7 @@ struct cpuidle_state {
 #define CPUIDLE_FLAG_TIMER_STOP BIT(2) /* timer is stopped on this state */
 #define CPUIDLE_FLAG_UNUSABLE	BIT(3) /* avoid using this state */
 #define CPUIDLE_FLAG_OFF	BIT(4) /* disable this state by default */
+#define CPUIDLE_FLAG_S2ILDE	BIT(5) /* state is used for s2idle only */
 
 struct cpuidle_device_kobj;
 struct cpuidle_state_kobj;
-- 
2.20.1