2  * ladder.c - the residency ladder algorithm
8  * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
32 	} threshold;  member
34 		int promotion_count;
35 		int demotion_count;
46  * ladder_do_selection - prepares private data for a state change
53 				       int old_idx, int new_idx)  in ladder_do_selection()
55 	ldev->states[old_idx].stats.promotion_count = 0;  in ladder_do_selection()
56 	ldev->states[old_idx].stats.demotion_count = 0;  in ladder_do_selection()
57 	dev->last_state_idx = new_idx;  in ladder_do_selection()
61  * ladder_select_state - selects the next state to enter
66 static int ladder_select_state(struct cpuidle_driver *drv,  in ladder_select_state()
71 	int last_idx = dev->last_state_idx;  in ladder_select_state()
72 	int first_idx = drv->states[0].flags & CPUIDLE_FLAG_POLLING ? 1 : 0;  in ladder_select_state()
73 	s64 latency_req = cpuidle_governor_latency_req(dev->cpu);  in ladder_select_state()
82 	last_state = &ldev->states[last_idx];  in ladder_select_state()
84 	last_residency = dev->last_residency_ns - drv->states[last_idx].exit_latency_ns;  in ladder_select_state()
87 	if (last_idx < drv->state_count - 1 &&  in ladder_select_state()
88 	    !dev->states_usage[last_idx + 1].disable &&  in ladder_select_state()
89 	    last_residency > last_state->threshold.promotion_time_ns &&  in ladder_select_state()
90 	    drv->states[last_idx + 1].exit_latency_ns <= latency_req) {  in ladder_select_state()
91 		last_state->stats.promotion_count++;  in ladder_select_state()
92 		last_state->stats.demotion_count = 0;  in ladder_select_state()
93 		if (last_state->stats.promotion_count >= last_state->threshold.promotion_count) {  in ladder_select_state()
101 	    (dev->states_usage[last_idx].disable ||  in ladder_select_state()
102 	    drv->states[last_idx].exit_latency_ns > latency_req)) {  in ladder_select_state()
103 		int i;  in ladder_select_state()
105 		for (i = last_idx - 1; i > first_idx; i--) {  in ladder_select_state()
106 			if (drv->states[i].exit_latency_ns <= latency_req)  in ladder_select_state()
114 	    last_residency < last_state->threshold.demotion_time_ns) {  in ladder_select_state()
115 		last_state->stats.demotion_count++;  in ladder_select_state()
116 		last_state->stats.promotion_count = 0;  in ladder_select_state()
117 		if (last_state->stats.demotion_count >= last_state->threshold.demotion_count) {  in ladder_select_state()
118 			ladder_do_selection(dev, ldev, last_idx, last_idx - 1);  in ladder_select_state()
119 			return last_idx - 1;  in ladder_select_state()
128  * ladder_enable_device - setup for the governor
132 static int ladder_enable_device(struct cpuidle_driver *drv,  in ladder_enable_device()
135 	int i;  in ladder_enable_device()
136 	int first_idx = drv->states[0].flags & CPUIDLE_FLAG_POLLING ? 1 : 0;  in ladder_enable_device()
137 	struct ladder_device *ldev = &per_cpu(ladder_devices, dev->cpu);  in ladder_enable_device()
141 	dev->last_state_idx = first_idx;  in ladder_enable_device()
143 	for (i = first_idx; i < drv->state_count; i++) {  in ladder_enable_device()
144 		state = &drv->states[i];  in ladder_enable_device()
145 		lstate = &ldev->states[i];  in ladder_enable_device()
147 		lstate->stats.promotion_count = 0;  in ladder_enable_device()
148 		lstate->stats.demotion_count = 0;  in ladder_enable_device()
150 		lstate->threshold.promotion_count = PROMOTION_COUNT;  in ladder_enable_device()
151 		lstate->threshold.demotion_count = DEMOTION_COUNT;  in ladder_enable_device()
153 		if (i < drv->state_count - 1)  in ladder_enable_device()
154 			lstate->threshold.promotion_time_ns = state->exit_latency_ns;  in ladder_enable_device()
156 			lstate->threshold.demotion_time_ns = state->exit_latency_ns;  in ladder_enable_device()
163  * ladder_reflect - update the correct last_state_idx
167 static void ladder_reflect(struct cpuidle_device *dev, int index)  in ladder_reflect()
170 		dev->last_state_idx = index;  in ladder_reflect()
182  * init_ladder - initializes the governor
184 static int __init init_ladder(void)  in init_ladder()