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