cpuidle: Consolidate disabled state checks

There are two reasons why CPU idle states may be disabled: either
because the driver has disabled them or because they have been
disabled by user space via sysfs.

In the former case, the state's "disabled" flag is set once during
the initialization of the driver and it is never cleared later (it
is read-only effectively). In the latter case, the "disable" field
of the given state's cpuidle_state_usage struct is set and it may be
changed via sysfs. Thus checking whether or not an idle state has
been disabled involves reading these two flags every time.

In order to avoid the additional check of the state's "disabled" flag
(which is effectively read-only anyway), use the value of it at the
init time to set a (new) flag in the "disable" field of that state's
cpuidle_state_usage structure and use the sysfs interface to
manipulate another (new) flag in it. This way the state is disabled
whenever the "disable" field of its cpuidle_state_usage structure is
nonzero, whatever the reason, and it is the only place to look into
to check whether or not the state has been disabled.

Signed-off-by: Rafael J. Wysocki <[e-mail]>
Acked-by: Daniel Lezcano <[e-mail]>
Acked-by: Peter Zijlstra (Intel) <[e-mail]>

drivers/cpuidle/cpuidle-powernv.c

···
 		return default_snooze_timeout;
 
 	for (i = index + 1; 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)
+		if (dev->states_usage[i].disable)
 			continue;
 
-		return s->target_residency * tb_ticks_per_usec;
+		return drv->states[i].target_residency * tb_ticks_per_usec;
 	}
 
 	return default_snooze_timeout;

drivers/cpuidle/cpuidle.c

···
 
 	for (i = 1; 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 || s->exit_latency <= latency_req
-		    || s->exit_latency > max_latency
-		    || (s->flags & forbidden_flags)
-		    || (s2idle && !s->enter_s2idle))
+		if (dev->states_usage[i].disable ||
+		    s->exit_latency <= latency_req ||
+		    s->exit_latency > max_latency ||
+		    (s->flags & forbidden_flags) ||
+		    (s2idle && !s->enter_s2idle))
 			continue;
 
 		latency_req = s->exit_latency;
···
 
 		if (diff < drv->states[entered_state].target_residency) {
 			for (i = entered_state - 1; i >= 0; i--) {
-				if (drv->states[i].disabled ||
-				    dev->states_usage[i].disable)
+				if (dev->states_usage[i].disable)
 					continue;
 
 				/* Shallower states are enabled, so update. */
···
 			}
 		} else if (diff > delay) {
 			for (i = entered_state + 1; i < drv->state_count; i++) {
-				if (drv->states[i].disabled ||
-				    dev->states_usage[i].disable)
+				if (dev->states_usage[i].disable)
 					continue;
 
 				/*
···
 
 	limit_ns = TICK_NSEC;
 	for (i = 1; i < drv->state_count; i++) {
-		if (drv->states[i].disabled || dev->states_usage[i].disable)
+		if (dev->states_usage[i].disable)
 			continue;
 
 		limit_ns = (u64)drv->states[i].target_residency * NSEC_PER_USEC;
···
  */
 static int __cpuidle_register_device(struct cpuidle_device *dev)
 {
-	int ret;
 	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
+	int i, ret;
 
 	if (!try_module_get(drv->owner))
 		return -EINVAL;
+
+	for (i = 0; i < drv->state_count; i++)
+		if (drv->states[i].disabled)
+			dev->states_usage[i].disable |= CPUIDLE_STATE_DISABLED_BY_DRIVER;
 
 	per_cpu(cpuidle_devices, dev->cpu) = dev;
 	list_add(&dev->device_list, &cpuidle_detected_devices);

drivers/cpuidle/governors/ladder.c

···
 
 	/* consider promotion */
 	if (last_idx < drv->state_count - 1 &&
-	    !drv->states[last_idx + 1].disabled &&
 	    !dev->states_usage[last_idx + 1].disable &&
 	    last_residency > last_state->threshold.promotion_time &&
 	    drv->states[last_idx + 1].exit_latency <= latency_req) {
···
 
 	/* consider demotion */
 	if (last_idx > first_idx &&
-	    (drv->states[last_idx].disabled ||
-	    dev->states_usage[last_idx].disable ||
+	    (dev->states_usage[last_idx].disable ||
 	    drv->states[last_idx].exit_latency > latency_req)) {
 		int i;
 

drivers/cpuidle/governors/menu.c

···
 	if (unlikely(drv->state_count <= 1 || latency_req == 0) ||
 	    ((data->next_timer_us < drv->states[1].target_residency ||
 	      latency_req < drv->states[1].exit_latency) &&
-	     !drv->states[0].disabled && !dev->states_usage[0].disable)) {
+	     !dev->states_usage[0].disable)) {
 		/*
 		 * In this case state[0] will be used no matter what, so return
 		 * it right away and keep the tick running if state[0] is a
···
 	idx = -1;
 	for (i = 0; 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)
+		if (dev->states_usage[i].disable)
 			continue;
 
 		if (idx == -1)
···
 			 * tick, so try to correct that.
 			 */
 			for (i = idx - 1; i >= 0; i--) {
-				if (drv->states[i].disabled ||
-				    dev->states_usage[i].disable)
+				if (dev->states_usage[i].disable)
 					continue;
 
 				idx = i;

drivers/cpuidle/governors/teo.c

···
 	int i;
 
 	for (i = state_idx - 1; i >= 0; i--) {
-		if (drv->states[i].disabled || dev->states_usage[i].disable)
+		if (dev->states_usage[i].disable)
 			continue;
 
 		state_idx = i;
···
 
 	for (i = 0; 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) {
+		if (dev->states_usage[i].disable) {
 			/*
 			 * Ignore disabled states with target residencies beyond
 			 * the anticipated idle duration.

drivers/cpuidle/sysfs.c

···
 	return sprintf(buf, "%u\n", state->_name);\
 }
 
-#define define_store_state_ull_function(_name) \
-static ssize_t store_state_##_name(struct cpuidle_state *state, \
-				   struct cpuidle_state_usage *state_usage, \
-				   const char *buf, size_t size)	\
-{ \
-	unsigned long long value; \
-	int err; \
-	if (!capable(CAP_SYS_ADMIN)) \
-		return -EPERM; \
-	err = kstrtoull(buf, 0, &value); \
-	if (err) \
-		return err; \
-	if (value) \
-		state_usage->_name = 1; \
-	else \
-		state_usage->_name = 0; \
-	return size; \
-}
-
 #define define_show_state_ull_function(_name) \
 static ssize_t show_state_##_name(struct cpuidle_state *state, \
 				  struct cpuidle_state_usage *state_usage, \
···
 define_show_state_ull_function(time)
 define_show_state_str_function(name)
 define_show_state_str_function(desc)
-define_show_state_ull_function(disable)
-define_store_state_ull_function(disable)
 define_show_state_ull_function(above)
 define_show_state_ull_function(below)
+
+static ssize_t show_state_disable(struct cpuidle_state *state,
+				  struct cpuidle_state_usage *state_usage,
+				  char *buf)
+{
+	return sprintf(buf, "%llu\n",
+		       state_usage->disable & CPUIDLE_STATE_DISABLED_BY_USER);
+}
+
+static ssize_t store_state_disable(struct cpuidle_state *state,
+				   struct cpuidle_state_usage *state_usage,
+				   const char *buf, size_t size)
+{
+	unsigned int value;
+	int err;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	err = kstrtouint(buf, 0, &value);
+	if (err)
+		return err;
+
+	if (value)
+		state_usage->disable |= CPUIDLE_STATE_DISABLED_BY_USER;
+	else
+		state_usage->disable &= ~CPUIDLE_STATE_DISABLED_BY_USER;
+
+	return size;
+}
 
 define_one_state_ro(name, show_state_name);
 define_one_state_ro(desc, show_state_desc);

include/linux/cpuidle.h

···
  * CPUIDLE DEVICE INTERFACE *
  ****************************/
 
+#define CPUIDLE_STATE_DISABLED_BY_USER		BIT(0)
+#define CPUIDLE_STATE_DISABLED_BY_DRIVER	BIT(1)
+
 struct cpuidle_state_usage {
 	unsigned long long	disable;
 	unsigned long long	usage;