From b891f9c43af71a7f2070c2cc93f52e8da907e333 Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@gmail.com>
Date: Mon, 26 Jun 2017 15:38:15 +1000
Subject: [PATCH] cpuidle: menu: allow state 0 to be disabled

References: bnc#1068680 Update schedutil and intel_pstate to default to load-based policy
Patch-mainline: v4.13-rc1
Git-commit: 3ed09c94580de9d5b18cc35d1f97e9f24cd9233b

The menu driver does not allow state0 to be disabled completely.
If it is disabled but other enabled states don't meet latency
requirements, it is still used.

Fix this by starting with the first enabled idle state. Fall back
to state 0 if no idle states are enabled (arguably this should be
-EINVAL if it is attempted, but this is the minimal fix).

Acked-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 drivers/cpuidle/governors/menu.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index b2330fd69e34..61b64c2b2cb8 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -286,6 +286,8 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 	struct device *device = get_cpu_device(dev->cpu);
 	int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
 	int i;
+	int first_idx;
+	int idx;
 	unsigned int interactivity_req;
 	unsigned int expected_interval;
 	unsigned long nr_iowaiters, cpu_load;
@@ -335,11 +337,11 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 		if (data->next_timer_us > polling_threshold &&
 		    latency_req > s->exit_latency && !s->disabled &&
 		    !dev->states_usage[CPUIDLE_DRIVER_STATE_START].disable)
-			data->last_state_idx = CPUIDLE_DRIVER_STATE_START;
+			first_idx = CPUIDLE_DRIVER_STATE_START;
 		else
-			data->last_state_idx = CPUIDLE_DRIVER_STATE_START - 1;
+			first_idx = CPUIDLE_DRIVER_STATE_START - 1;
 	} else {
-		data->last_state_idx = CPUIDLE_DRIVER_STATE_START;
+		first_idx = 0;
 	}
 
 	/*
@@ -359,20 +361,28 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 	 * Find the idle state with the lowest power while satisfying
 	 * our constraints.
 	 */
-	for (i = data->last_state_idx + 1; i < drv->state_count; i++) {
+	idx = -1;
+	for (i = first_idx; i < drv->state_count; i++) {
 		struct cpuidle_state *s = &drv->states[i];
 		struct cpuidle_state_usage *su = &dev->states_usage[i];
 
 		if (s->disabled || su->disable)
 			continue;
+		if (idx == -1)
+			idx = i; /* first enabled state */
 		if (s->target_residency > data->predicted_us)
 			break;
 		if (s->exit_latency > latency_req)
 			break;
 
-		data->last_state_idx = i;
+		idx = i;
 	}
 
+	if (idx == -1)
+		idx = 0; /* No states enabled. Must use 0. */
+
+	data->last_state_idx = idx;
+
 	return data->last_state_idx;
 }