[PATCH] powerpc/cpuidle: Set CPUIDLE_FLAG_POLLING for snooze state

* [PATCH] powerpc/cpuidle: Set CPUIDLE_FLAG_POLLING for snooze state
@ 2022-11-14  7:31 Aboorva Devarajan
  2022-11-14 14:56 ` [PATCH v2] " Aboorva Devarajan
  0 siblings, 1 reply; 5+ messages in thread
From: Aboorva Devarajan @ 2022-11-14  7:31 UTC (permalink / raw)
  To: mpe, svaidy, rafael, daniel.lezcano, npiggin
  Cc: Aboorva Devarajan, linuxppc-dev, srikar, linux-pm

During the comparative study of cpuidle governors, it is noticed that the
menu governor does not select CEDE state in some scenarios even though when
the sleep duration of the CPU exceeds the target residency of the CEDE idle
state this is because the CPU exits the snooze "polling" state when snooze 
time limit is reached in the snooze_loop(), which is not a real wake up 
and it just means that the polling state selection was not adequate.

cpuidle governors rely on CPUIDLE_FLAG_POLLING flag to be set for the
polling states to handle the condition mentioned above.

Hence, set the CPUIDLE_FLAG_POLLING flag for the snooze state (polling state)
in powerpc arch to make the cpuidle governor work as expected.

Reference Commits:

- Timeout enabled for snooze state:
  commit 78eaa10f027c
  ("cpuidle: powernv/pseries: Auto-promotion of snooze to deeper idle state")

- commit dc2251bf98c6
  ("cpuidle: Eliminate the CPUIDLE_DRIVER_STATE_START symbol")

- Fix wakeup stats in governor for polling states
  commit 5f26bdceb9c0
  ("cpuidle: menu: Fix wakeup statistics updates for polling state")

Signed-off-by: Aboorva Devarajan <aboorvad@linux.vnet.ibm.com>
---
 drivers/cpuidle/cpuidle-powernv.c | 5 ++++-
 drivers/cpuidle/cpuidle-pseries.c | 8 ++++++--
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index 0b5461b3d7dd..9ebedd972df0 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c
@@ -76,6 +76,7 @@ static int snooze_loop(struct cpuidle_device *dev,
 	local_irq_enable();
 
 	snooze_exit_time = get_tb() + get_snooze_timeout(dev, drv, index);
+	dev->poll_time_limit = false;
 	ppc64_runlatch_off();
 	HMT_very_low();
 	while (!need_resched()) {
@@ -86,6 +87,7 @@ static int snooze_loop(struct cpuidle_device *dev,
 			 * cleared to order subsequent test of need_resched().
 			 */
 			clear_thread_flag(TIF_POLLING_NRFLAG);
+			dev->poll_time_limit = true;
 			smp_mb();
 			break;
 		}
@@ -155,7 +157,8 @@ static struct cpuidle_state powernv_states[CPUIDLE_STATE_MAX] = {
 		.desc = "snooze",
 		.exit_latency = 0,
 		.target_residency = 0,
-		.enter = snooze_loop },
+		.enter = snooze_loop,
+		.flags = CPUIDLE_FLAG_POLLING },
 };
 
 static int powernv_cpuidle_cpu_online(unsigned int cpu)
diff --git a/drivers/cpuidle/cpuidle-pseries.c b/drivers/cpuidle/cpuidle-pseries.c
index 7e7ab5597d7a..7538aa63f972 100644
--- a/drivers/cpuidle/cpuidle-pseries.c
+++ b/drivers/cpuidle/cpuidle-pseries.c
@@ -44,6 +44,7 @@ static int snooze_loop(struct cpuidle_device *dev,
 	pseries_idle_prolog();
 	local_irq_enable();
 	snooze_exit_time = get_tb() + snooze_timeout;
+	dev->poll_time_limit = false;
 
 	while (!need_resched()) {
 		HMT_low();
@@ -54,6 +55,7 @@ static int snooze_loop(struct cpuidle_device *dev,
 			 * loop anyway. Require a barrier after polling is
 			 * cleared to order subsequent test of need_resched().
 			 */
+			dev->poll_time_limit = true;
 			clear_thread_flag(TIF_POLLING_NRFLAG);
 			smp_mb();
 			break;
@@ -268,13 +270,15 @@ static struct cpuidle_state dedicated_states[NR_DEDICATED_STATES] = {
 		.desc = "snooze",
 		.exit_latency = 0,
 		.target_residency = 0,
-		.enter = &snooze_loop },
+		.enter = &snooze_loop,
+		.flags = CPUIDLE_FLAG_POLLING },
 	{ /* CEDE */
 		.name = "CEDE",
 		.desc = "CEDE",
 		.exit_latency = 10,
 		.target_residency = 100,
-		.enter = &dedicated_cede_loop },
+		.enter = &snooze_loop,
+		.flags = CPUIDLE_FLAG_POLLING },
 };
 
 /*
-- 
2.17.1


^ permalink raw reply related	[flat|nested] 5+ messages in thread