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/init.h>
 10#include <linux/kernel.h>
 11#include <linux/pm_domain.h>
 12#include <linux/pm_qos.h>
 13#include <linux/hrtimer.h>
 14
 15#ifdef CONFIG_PM_RUNTIME
 16
 17static int dev_update_qos_constraint(struct device *dev, void *data)
 18{
 19	s64 *constraint_ns_p = data;
 20	s32 constraint_ns = -1;
 21
 22	if (dev->power.subsys_data && dev->power.subsys_data->domain_data)
 23		constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns;
 24
 25	if (constraint_ns < 0) {
 26		constraint_ns = dev_pm_qos_read_value(dev);
 27		constraint_ns *= NSEC_PER_USEC;
 28	}
 29	if (constraint_ns == 0)
 30		return 0;
 31
 32	/*
 33	 * constraint_ns cannot be negative here, because the device has been
 34	 * suspended.
 35	 */
 36	if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0)
 37		*constraint_ns_p = constraint_ns;
 38
 39	return 0;
 40}
 41
 42/**
 43 * default_stop_ok - Default PM domain governor routine for stopping devices.
 44 * @dev: Device to check.
 45 */
 46bool default_stop_ok(struct device *dev)
 47{
 48	struct gpd_timing_data *td = &dev_gpd_data(dev)->td;
 49	unsigned long flags;
 50	s64 constraint_ns;
 51
 52	dev_dbg(dev, "%s()\n", __func__);
 53
 54	spin_lock_irqsave(&dev->power.lock, flags);
 55
 56	if (!td->constraint_changed) {
 57		bool ret = td->cached_stop_ok;
 58
 59		spin_unlock_irqrestore(&dev->power.lock, flags);
 60		return ret;
 61	}
 62	td->constraint_changed = false;
 63	td->cached_stop_ok = false;
 64	td->effective_constraint_ns = -1;
 65	constraint_ns = __dev_pm_qos_read_value(dev);
 66
 67	spin_unlock_irqrestore(&dev->power.lock, flags);
 68
 69	if (constraint_ns < 0)
 70		return false;
 71
 72	constraint_ns *= NSEC_PER_USEC;
 73	/*
 74	 * We can walk the children without any additional locking, because
 75	 * they all have been suspended at this point and their
 76	 * effective_constraint_ns fields won't be modified in parallel with us.
 77	 */
 78	if (!dev->power.ignore_children)
 79		device_for_each_child(dev, &constraint_ns,
 80				      dev_update_qos_constraint);
 81
 82	if (constraint_ns > 0) {
 83		constraint_ns -= td->start_latency_ns;
 84		if (constraint_ns == 0)
 85			return false;
 86	}
 87	td->effective_constraint_ns = constraint_ns;
 88	td->cached_stop_ok = constraint_ns > td->stop_latency_ns ||
 89				constraint_ns == 0;
 90	/*
 91	 * The children have been suspended already, so we don't need to take
 92	 * their stop latencies into account here.
 93	 */
 94	return td->cached_stop_ok;
 95}
 96
 97/**
 98 * default_power_down_ok - Default generic PM domain power off governor routine.
 99 * @pd: PM domain to check.
100 *
101 * This routine must be executed under the PM domain's lock.
102 */
103static bool default_power_down_ok(struct dev_pm_domain *pd)
104{
105	struct generic_pm_domain *genpd = pd_to_genpd(pd);
106	struct gpd_link *link;
107	struct pm_domain_data *pdd;
108	s64 min_off_time_ns;
109	s64 off_on_time_ns;
110
111	if (genpd->max_off_time_changed) {
112		struct gpd_link *link;
113
114		/*
115		 * We have to invalidate the cached results for the masters, so
116		 * use the observation that default_power_down_ok() is not
117		 * going to be called for any master until this instance
118		 * returns.
119		 */
120		list_for_each_entry(link, &genpd->slave_links, slave_node)
121			link->master->max_off_time_changed = true;
122
123		genpd->max_off_time_changed = false;
124		genpd->cached_power_down_ok = false;
125		genpd->max_off_time_ns = -1;
126	} else {
127		return genpd->cached_power_down_ok;
128	}
129
130	off_on_time_ns = genpd->power_off_latency_ns +
131				genpd->power_on_latency_ns;
132	/*
133	 * It doesn't make sense to remove power from the domain if saving
134	 * the state of all devices in it and the power off/power on operations
135	 * take too much time.
136	 *
137	 * All devices in this domain have been stopped already at this point.
138	 */
139	list_for_each_entry(pdd, &genpd->dev_list, list_node) {
140		if (pdd->dev->driver)
141			off_on_time_ns +=
142				to_gpd_data(pdd)->td.save_state_latency_ns;
143	}
144
145	min_off_time_ns = -1;
146	/*
147	 * Check if subdomains can be off for enough time.
148	 *
149	 * All subdomains have been powered off already at this point.
150	 */
151	list_for_each_entry(link, &genpd->master_links, master_node) {
152		struct generic_pm_domain *sd = link->slave;
153		s64 sd_max_off_ns = sd->max_off_time_ns;
154
155		if (sd_max_off_ns < 0)
156			continue;
157
158		/*
159		 * Check if the subdomain is allowed to be off long enough for
160		 * the current domain to turn off and on (that's how much time
161		 * it will have to wait worst case).
162		 */
163		if (sd_max_off_ns <= off_on_time_ns)
164			return false;
165
166		if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
167			min_off_time_ns = sd_max_off_ns;
168	}
169
170	/*
171	 * Check if the devices in the domain can be off enough time.
172	 */
173	list_for_each_entry(pdd, &genpd->dev_list, list_node) {
174		struct gpd_timing_data *td;
175		s64 constraint_ns;
176
177		if (!pdd->dev->driver)
178			continue;
179
180		/*
181		 * Check if the device is allowed to be off long enough for the
182		 * domain to turn off and on (that's how much time it will
183		 * have to wait worst case).
184		 */
185		td = &to_gpd_data(pdd)->td;
186		constraint_ns = td->effective_constraint_ns;
187		/* default_stop_ok() need not be called before us. */
188		if (constraint_ns < 0) {
189			constraint_ns = dev_pm_qos_read_value(pdd->dev);
190			constraint_ns *= NSEC_PER_USEC;
191		}
192		if (constraint_ns == 0)
193			continue;
194
195		/*
196		 * constraint_ns cannot be negative here, because the device has
197		 * been suspended.
198		 */
199		constraint_ns -= td->restore_state_latency_ns;
200		if (constraint_ns <= off_on_time_ns)
201			return false;
202
203		if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
204			min_off_time_ns = constraint_ns;
205	}
206
207	genpd->cached_power_down_ok = true;
208
209	/*
210	 * If the computed minimum device off time is negative, there are no
211	 * latency constraints, so the domain can spend arbitrary time in the
212	 * "off" state.
213	 */
214	if (min_off_time_ns < 0)
215		return true;
216
217	/*
218	 * The difference between the computed minimum subdomain or device off
219	 * time and the time needed to turn the domain on is the maximum
220	 * theoretical time this domain can spend in the "off" state.
221	 */
222	genpd->max_off_time_ns = min_off_time_ns - genpd->power_on_latency_ns;
223	return true;
224}
225
226static bool always_on_power_down_ok(struct dev_pm_domain *domain)
227{
228	return false;
229}
230
231#else /* !CONFIG_PM_RUNTIME */
232
233bool default_stop_ok(struct device *dev)
234{
235	return false;
236}
237
238#define default_power_down_ok	NULL
239#define always_on_power_down_ok	NULL
240
241#endif /* !CONFIG_PM_RUNTIME */
242
243struct dev_power_governor simple_qos_governor = {
244	.stop_ok = default_stop_ok,
245	.power_down_ok = default_power_down_ok,
246};
247
248/**
249 * pm_genpd_gov_always_on - A governor implementing an always-on policy
250 */
251struct dev_power_governor pm_domain_always_on_gov = {
252	.power_down_ok = always_on_power_down_ok,
253	.stop_ok = default_stop_ok,
254};