cpuidle: Eliminate the CPUIDLE_DRIVER_STATE_START symbol

On some architectures the first (index 0) idle state is a polling
one and it doesn't really save energy, so there is the
CPUIDLE_DRIVER_STATE_START symbol allowing some pieces of
cpuidle code to avoid using that state.

However, this makes the code rather hard to follow.  It is better
to explicitly avoid the polling state, so add a new cpuidle state
flag CPUIDLE_FLAG_POLLING to mark it and make the relevant code
check that flag for the first state instead of using the
CPUIDLE_DRIVER_STATE_START symbol.

In the ACPI processor driver that cannot always rely on the state
flags (like before the states table has been set up) define
a new internal symbol ACPI_IDLE_STATE_START equivalent to the
CPUIDLE_DRIVER_STATE_START one and drop the latter.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>

3 files changed, 14 insertions, 14 deletions

diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
index e53fb86..e942f8e 100644
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -204,6 +204,7 @@ static void poll_idle_init(struct cpuidle_driver *drv)
 	state->power_usage = -1;
 	state->enter = poll_idle;
 	state->disabled = false;
+	state->flags = CPUIDLE_FLAG_POLLING;
 }
 #else
 static void poll_idle_init(struct cpuidle_driver *drv) {}
diff --git a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c
index ac321f0..ce1a2ff 100644
--- a/drivers/cpuidle/governors/ladder.c
+++ b/drivers/cpuidle/governors/ladder.c
@@ -69,6 +69,7 @@ static int ladder_select_state(struct cpuidle_driver *drv,
 	struct ladder_device *ldev = this_cpu_ptr(&ladder_devices);
 	struct ladder_device_state *last_state;
 	int last_residency, last_idx = ldev->last_state_idx;
+	int first_idx = drv->states[0].flags & CPUIDLE_FLAG_POLLING ? 1 : 0;
 	int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
 
 	/* Special case when user has set very strict latency requirement */
@@ -96,13 +97,13 @@ static int ladder_select_state(struct cpuidle_driver *drv,
 	}
 
 	/* consider demotion */
-	if (last_idx > CPUIDLE_DRIVER_STATE_START &&
+	if (last_idx > first_idx &&
 	    (drv->states[last_idx].disabled ||
 	    dev->states_usage[last_idx].disable ||
 	    drv->states[last_idx].exit_latency > latency_req)) {
 		int i;
 
-		for (i = last_idx - 1; i > CPUIDLE_DRIVER_STATE_START; i--) {
+		for (i = last_idx - 1; i > first_idx; i--) {
 			if (drv->states[i].exit_latency <= latency_req)
 				break;
 		}
@@ -110,7 +111,7 @@ static int ladder_select_state(struct cpuidle_driver *drv,
 		return i;
 	}
 
-	if (last_idx > CPUIDLE_DRIVER_STATE_START &&
+	if (last_idx > first_idx &&
 	    last_residency < last_state->threshold.demotion_time) {
 		last_state->stats.demotion_count++;
 		last_state->stats.promotion_count = 0;
@@ -133,13 +134,14 @@ static int ladder_enable_device(struct cpuidle_driver *drv,
 				struct cpuidle_device *dev)
 {
 	int i;
+	int first_idx = drv->states[0].flags & CPUIDLE_FLAG_POLLING ? 1 : 0;
 	struct ladder_device *ldev = &per_cpu(ladder_devices, dev->cpu);
 	struct ladder_device_state *lstate;
 	struct cpuidle_state *state;
 
-	ldev->last_state_idx = CPUIDLE_DRIVER_STATE_START;
+	ldev->last_state_idx = first_idx;
 
-	for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++) {
+	for (i = first_idx; i < drv->state_count; i++) {
 		state = &drv->states[i];
 		lstate = &ldev->states[i];
 
@@ -151,7 +153,7 @@ static int ladder_enable_device(struct cpuidle_driver *drv,
 
 		if (i < drv->state_count - 1)
 			lstate->threshold.promotion_time = state->exit_latency;
-		if (i > CPUIDLE_DRIVER_STATE_START)
+		if (i > first_idx)
 			lstate->threshold.demotion_time = state->exit_latency;
 	}
 
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 61b64c2..48eaf28 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -324,8 +324,9 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 	expected_interval = get_typical_interval(data);
 	expected_interval = min(expected_interval, data->next_timer_us);
 
-	if (CPUIDLE_DRIVER_STATE_START > 0) {
-		struct cpuidle_state *s = &drv->states[CPUIDLE_DRIVER_STATE_START];
+	first_idx = 0;
+	if (drv->states[0].flags & CPUIDLE_FLAG_POLLING) {
+		struct cpuidle_state *s = &drv->states[1];
 		unsigned int polling_threshold;
 
 		/*
@@ -336,12 +337,8 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 		polling_threshold = max_t(unsigned int, 20, s->target_residency);
 		if (data->next_timer_us > polling_threshold &&
 		    latency_req > s->exit_latency && !s->disabled &&
-		    !dev->states_usage[CPUIDLE_DRIVER_STATE_START].disable)
-			first_idx = CPUIDLE_DRIVER_STATE_START;
-		else
-			first_idx = CPUIDLE_DRIVER_STATE_START - 1;
-	} else {
-		first_idx = 0;
+		    !dev->states_usage[1].disable)
+			first_idx = 1;
 	}
 
 	/*