1/*
  2 * drivers/base/power/domain_governor.c - Governors for device PM domains.
  3 *
  4 * Copyright (C) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
  5 *
  6 * This file is released under the GPLv2.
  7 */
  8
  9#include <linux/kernel.h>
 10#include <linux/pm_domain.h>
 11#include <linux/pm_qos.h>
 12#include <linux/hrtimer.h>
 13
 14#ifdef CONFIG_PM_RUNTIME
 15
 16static int dev_update_qos_constraint(struct device *dev, void *data)
 17{
 18	s64 *constraint_ns_p = data;
 19	s32 constraint_ns = -1;
 20
 21	if (dev->power.subsys_data && dev->power.subsys_data->domain_data)
 22		constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns;
 23
 24	if (constraint_ns < 0) {
 25		constraint_ns = dev_pm_qos_read_value(dev);
 26		constraint_ns *= NSEC_PER_USEC;
 27	}
 28	if (constraint_ns == 0)
 29		return 0;
 30
 31	/*
 32	 * constraint_ns cannot be negative here, because the device has been
 33	 * suspended.
 34	 */
 35	if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0)
 36		*constraint_ns_p = constraint_ns;
 37
 38	return 0;
 39}
 40
 41/**
 42 * default_stop_ok - Default PM domain governor routine for stopping devices.
 43 * @dev: Device to check.
 44 */
 45bool default_stop_ok(struct device *dev)
 46{
 47	struct gpd_timing_data *td = &dev_gpd_data(dev)->td;
 48	unsigned long flags;
 49	s64 constraint_ns;
 50
 51	dev_dbg(dev, "%s()\n", __func__);
 52
 53	spin_lock_irqsave(&dev->power.lock, flags);
 54
 55	if (!td->constraint_changed) {
 56		bool ret = td->cached_stop_ok;
 57
 58		spin_unlock_irqrestore(&dev->power.lock, flags);
 59		return ret;
 60	}
 61	td->constraint_changed = false;
 62	td->cached_stop_ok = false;
 63	td->effective_constraint_ns = -1;
 64	constraint_ns = __dev_pm_qos_read_value(dev);
 65
 66	spin_unlock_irqrestore(&dev->power.lock, flags);
 67
 68	if (constraint_ns < 0)
 69		return false;
 70
 71	constraint_ns *= NSEC_PER_USEC;
 72	/*
 73	 * We can walk the children without any additional locking, because
 74	 * they all have been suspended at this point and their
 75	 * effective_constraint_ns fields won't be modified in parallel with us.
 76	 */
 77	if (!dev->power.ignore_children)
 78		device_for_each_child(dev, &constraint_ns,
 79				      dev_update_qos_constraint);
 80
 81	if (constraint_ns > 0) {
 82		constraint_ns -= td->start_latency_ns;
 83		if (constraint_ns == 0)
 84			return false;
 85	}
 86	td->effective_constraint_ns = constraint_ns;
 87	td->cached_stop_ok = constraint_ns > td->stop_latency_ns ||
 88				constraint_ns == 0;
 89	/*
 90	 * The children have been suspended already, so we don't need to take
 91	 * their stop latencies into account here.
 92	 */
 93	return td->cached_stop_ok;
 94}
 95
 96/**
 97 * default_power_down_ok - Default generic PM domain power off governor routine.
 98 * @pd: PM domain to check.
 99 *
100 * This routine must be executed under the PM domain's lock.
101 */
102static bool default_power_down_ok(struct dev_pm_domain *pd)
103{
104	struct generic_pm_domain *genpd = pd_to_genpd(pd);
105	struct gpd_link *link;
106	struct pm_domain_data *pdd;
107	s64 min_off_time_ns;
108	s64 off_on_time_ns;
109
110	if (genpd->max_off_time_changed) {
111		struct gpd_link *link;
112
113		/*
114		 * We have to invalidate the cached results for the masters, so
115		 * use the observation that default_power_down_ok() is not
116		 * going to be called for any master until this instance
117		 * returns.
118		 */
119		list_for_each_entry(link, &genpd->slave_links, slave_node)
120			link->master->max_off_time_changed = true;
121
122		genpd->max_off_time_changed = false;
123		genpd->cached_power_down_ok = false;
124		genpd->max_off_time_ns = -1;
125	} else {
126		return genpd->cached_power_down_ok;
127	}
128
129	off_on_time_ns = genpd->power_off_latency_ns +
130				genpd->power_on_latency_ns;
131	/*
132	 * It doesn't make sense to remove power from the domain if saving
133	 * the state of all devices in it and the power off/power on operations
134	 * take too much time.
135	 *
136	 * All devices in this domain have been stopped already at this point.
137	 */
138	list_for_each_entry(pdd, &genpd->dev_list, list_node) {
139		if (pdd->dev->driver)
140			off_on_time_ns +=
141				to_gpd_data(pdd)->td.save_state_latency_ns;
142	}
143
144	min_off_time_ns = -1;
145	/*
146	 * Check if subdomains can be off for enough time.
147	 *
148	 * All subdomains have been powered off already at this point.
149	 */
150	list_for_each_entry(link, &genpd->master_links, master_node) {
151		struct generic_pm_domain *sd = link->slave;
152		s64 sd_max_off_ns = sd->max_off_time_ns;
153
154		if (sd_max_off_ns < 0)
155			continue;
156
157		/*
158		 * Check if the subdomain is allowed to be off long enough for
159		 * the current domain to turn off and on (that's how much time
160		 * it will have to wait worst case).
161		 */
162		if (sd_max_off_ns <= off_on_time_ns)
163			return false;
164
165		if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
166			min_off_time_ns = sd_max_off_ns;
167	}
168
169	/*
170	 * Check if the devices in the domain can be off enough time.
171	 */
172	list_for_each_entry(pdd, &genpd->dev_list, list_node) {
173		struct gpd_timing_data *td;
174		s64 constraint_ns;
175
176		if (!pdd->dev->driver)
177			continue;
178
179		/*
180		 * Check if the device is allowed to be off long enough for the
181		 * domain to turn off and on (that's how much time it will
182		 * have to wait worst case).
183		 */
184		td = &to_gpd_data(pdd)->td;
185		constraint_ns = td->effective_constraint_ns;
186		/* default_stop_ok() need not be called before us. */
187		if (constraint_ns < 0) {
188			constraint_ns = dev_pm_qos_read_value(pdd->dev);
189			constraint_ns *= NSEC_PER_USEC;
190		}
191		if (constraint_ns == 0)
192			continue;
193
194		/*
195		 * constraint_ns cannot be negative here, because the device has
196		 * been suspended.
197		 */
198		constraint_ns -= td->restore_state_latency_ns;
199		if (constraint_ns <= off_on_time_ns)
200			return false;
201
202		if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
203			min_off_time_ns = constraint_ns;
204	}
205
206	genpd->cached_power_down_ok = true;
207
208	/*
209	 * If the computed minimum device off time is negative, there are no
210	 * latency constraints, so the domain can spend arbitrary time in the
211	 * "off" state.
212	 */
213	if (min_off_time_ns < 0)
214		return true;
215
216	/*
217	 * The difference between the computed minimum subdomain or device off
218	 * time and the time needed to turn the domain on is the maximum
219	 * theoretical time this domain can spend in the "off" state.
220	 */
221	genpd->max_off_time_ns = min_off_time_ns - genpd->power_on_latency_ns;
222	return true;
223}
224
225static bool always_on_power_down_ok(struct dev_pm_domain *domain)
226{
227	return false;
228}
229
230#else /* !CONFIG_PM_RUNTIME */
231
232bool default_stop_ok(struct device *dev)
233{
234	return false;
235}
236
237#define default_power_down_ok	NULL
238#define always_on_power_down_ok	NULL
239
240#endif /* !CONFIG_PM_RUNTIME */
241
242struct dev_power_governor simple_qos_governor = {
243	.stop_ok = default_stop_ok,
244	.power_down_ok = default_power_down_ok,
245};
246
247/**
248 * pm_genpd_gov_always_on - A governor implementing an always-on policy
249 */
250struct dev_power_governor pm_domain_always_on_gov = {
251	.power_down_ok = always_on_power_down_ok,
252	.stop_ok = default_stop_ok,
253};