[RFC PATCH 2/4] cpuidle: menu: add idle_time to cpuidle_state

[Sowjanya Komatineni <skomatineni@nvidia.com>]

Some platforms use separate CPU firmware running in background to
handle state transitions which may need runtime idle time of the
corresponding target state from the kernel.

This patch adds idle_time to cpuidle state to expose to cpuidle driver the
idle time that the governor menu predicts based on next events and states
target residency for selecting proper idle state.

CPU idle driver passes this runtime state idle time to TF-A.

Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
---
 drivers/cpuidle/governors/menu.c | 7 ++++++-
 include/linux/cpuidle.h          | 1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index c3aa8d6..0da5bc5 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -382,8 +382,10 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 			 * stuck in the shallow one for too long.
 			 */
 			if (drv->states[idx].target_residency_ns < TICK_NSEC &&
-			    s->target_residency_ns <= delta_tick)
+			    s->target_residency_ns <= delta_tick) {
+				drv->states[idx].idle_time = delta_tick / NSEC_PER_USEC;
 				idx = i;
+			}
 
 			return idx;
 		}
@@ -393,6 +395,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 		idx = i;
 	}
 
+	drv->states[idx].idle_time = predicted_ns / NSEC_PER_USEC;
 	if (idx == -1)
 		idx = 0; /* No states enabled. Must use 0. */
 
@@ -419,6 +422,8 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 				if (drv->states[i].target_residency_ns <= delta_tick)
 					break;
 			}
+
+			drv->states[idx].idle_time = delta_tick / NSEC_PER_USEC;
 		}
 	}
 
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index fce4762..12db2e9 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -55,6 +55,7 @@ struct cpuidle_state {
 	unsigned int	exit_latency; /* in US */
 	int		power_usage; /* in mW */
 	unsigned int	target_residency; /* in US */
+	unsigned int	idle_time; /* in US */
 
 	int (*enter)	(struct cpuidle_device *dev,
 			struct cpuidle_driver *drv,
-- 
2.7.4