/* * ladder.c - the residency ladder algorithm * *  Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com> *  Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com> *  Copyright (C) 2004, 2005 Dominik Brodowski <linux@brodo.de> * * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> *               Shaohua Li <shaohua.li@intel.com> *               Adam Belay <abelay@novell.com> * * This code is licenced under the GPL. */#include <linux/kernel.h>#include <linux/cpuidle.h>#include <linux/latency.h>#include <linux/moduleparam.h>#include <linux/jiffies.h>#include <asm/io.h>#include <asm/uaccess.h>#define PROMOTION_COUNT 4#define DEMOTION_COUNT 1struct ladder_device_state {	struct {		u32 promotion_count;		u32 demotion_count;		u32 promotion_time;		u32 demotion_time;	} threshold;	struct {		int promotion_count;		int demotion_count;	} stats;};struct ladder_device {	struct ladder_device_state states[CPUIDLE_STATE_MAX];	int last_state_idx;};static DEFINE_PER_CPU(struct ladder_device, ladder_devices);/** * ladder_do_selection - prepares private data for a state change * @ldev: the ladder device * @old_idx: the current state index * @new_idx: the new target state index */static inline void ladder_do_selection(struct ladder_device *ldev,				       int old_idx, int new_idx){	ldev->states[old_idx].stats.promotion_count = 0;	ldev->states[old_idx].stats.demotion_count = 0;	ldev->last_state_idx = new_idx;}/** * ladder_select_state - selects the next state to enter * @dev: the CPU */static int ladder_select_state(struct cpuidle_device *dev){	struct ladder_device *ldev = &__get_cpu_var(ladder_devices);	struct ladder_device_state *last_state;	int last_residency, last_idx = ldev->last_state_idx;	if (unlikely(!ldev))		return 0;	last_state = &ldev->states[last_idx];	if (dev->states[last_idx].flags & CPUIDLE_FLAG_TIME_VALID)		last_residency = cpuidle_get_last_residency(dev) - dev->states[last_idx].exit_latency;	else		last_residency = last_state->threshold.promotion_time + 1;	/* consider promotion */	if (last_idx < dev->state_count - 1 &&	    last_residency > last_state->threshold.promotion_time &&	    dev->states[last_idx + 1].exit_latency <= system_latency_constraint()) {		last_state->stats.promotion_count++;		last_state->stats.demotion_count = 0;		if (last_state->stats.promotion_count >= last_state->threshold.promotion_count) {			ladder_do_selection(ldev, last_idx, last_idx + 1);			return last_idx + 1;		}	}	/* consider demotion */	if (last_idx > 0 &&	    last_residency < last_state->threshold.demotion_time) {		last_state->stats.demotion_count++;		last_state->stats.promotion_count = 0;		if (last_state->stats.demotion_count >= last_state->threshold.demotion_count) {			ladder_do_selection(ldev, last_idx, last_idx - 1);			return last_idx - 1;		}	}	/* otherwise remain at the current state */	return last_idx;}/** * ladder_enable_device - setup for the governor * @dev: the CPU */static int ladder_enable_device(struct cpuidle_device *dev){	int i;	struct ladder_device *ldev = &per_cpu(ladder_devices, dev->cpu);	struct ladder_device_state *lstate;	struct cpuidle_state *state;	ldev->last_state_idx = 0;	for (i = 0; i < dev->state_count; i++) {		state = &dev->states[i];		lstate = &ldev->states[i];		lstate->stats.promotion_count = 0;		lstate->stats.demotion_count = 0;		lstate->threshold.promotion_count = PROMOTION_COUNT;		lstate->threshold.demotion_count = DEMOTION_COUNT;		if (i < dev->state_count - 1)			lstate->threshold.promotion_time = state->exit_latency;		if (i > 0)			lstate->threshold.demotion_time = state->exit_latency;	}	return 0;}static struct cpuidle_governor ladder_governor = {	.name =		"ladder",	.rating =	10,	.enable =	ladder_enable_device,	.select =	ladder_select_state,	.owner =	THIS_MODULE,};/** * init_ladder - initializes the governor */static int __init init_ladder(void){	return cpuidle_register_governor(&ladder_governor);}/** * exit_ladder - exits the governor */static void __exit exit_ladder(void){	cpuidle_unregister_governor(&ladder_governor);}MODULE_LICENSE("GPL");module_init(init_ladder);module_exit(exit_ladder);