linux-kernel - [RFC PATCH v4 1/2] cpuidle: teo: Optionally skip polling states in teo_find_shallower

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Message-Id: <20221102152808.2978590-2-kajetan.puchalski@arm.com>
Date:   Wed,  2 Nov 2022 15:28:07 +0000
From:   Kajetan Puchalski <kajetan.puchalski@....com>
To:     rafael@...nel.org
Cc:     daniel.lezcano@...aro.org, lukasz.luba@....com,
        Dietmar.Eggemann@....com, dsmythies@...us.net,
        yu.chen.surf@...il.com, kajetan.puchalski@....com,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v4 1/2] cpuidle: teo: Optionally skip polling states in teo_find_shallower_state()

Add a no_poll flag to teo_find_shallower_state() that will let the
function optionally not consider polling states.
This allows the caller to guard against the function inadvertently
resulting in TEO putting the CPU in a polling state when that
behaviour is undesirable.

Signed-off-by: Kajetan Puchalski <kajetan.puchalski@....com>
---
 drivers/cpuidle/governors/teo.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/cpuidle/governors/teo.c b/drivers/cpuidle/governors/teo.c
index d9262db79cae..e2864474a98d 100644
--- a/drivers/cpuidle/governors/teo.c
+++ b/drivers/cpuidle/governors/teo.c
@@ -258,15 +258,17 @@ static s64 teo_middle_of_bin(int idx, struct cpuidle_driver *drv)
  * @dev: Target CPU.
  * @state_idx: Index of the capping idle state.
  * @duration_ns: Idle duration value to match.
+ * @no_poll: Don't consider polling states.
  */
 static int teo_find_shallower_state(struct cpuidle_driver *drv,
 				    struct cpuidle_device *dev, int state_idx,
-				    s64 duration_ns)
+				    s64 duration_ns, bool no_poll)
 {
 	int i;
 
 	for (i = state_idx - 1; i >= 0; i--) {
-		if (dev->states_usage[i].disable)
+		if (dev->states_usage[i].disable ||
+				(no_poll && drv->states[i].flags & CPUIDLE_FLAG_POLLING))
 			continue;
 
 		state_idx = i;
@@ -469,7 +471,7 @@ static int teo_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 		 */
 		if (idx > idx0 &&
 		    drv->states[idx].target_residency_ns > delta_tick)
-			idx = teo_find_shallower_state(drv, dev, idx, delta_tick);
+			idx = teo_find_shallower_state(drv, dev, idx, delta_tick, false);
 	}
 
 	return idx;
-- 
2.37.1