1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * drivers/base/power/domain_governor.c - Governors for device PM domains. 4 * 5 * Copyright (C) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp. 6 */ 7 #include <linux/kernel.h> 8 #include <linux/pm_domain.h> 9 #include <linux/pm_qos.h> 10 #include <linux/hrtimer.h> 11 #include <linux/cpuidle.h> 12 #include <linux/cpumask.h> 13 #include <linux/ktime.h> 14 15 static int dev_update_qos_constraint(struct device *dev, void *data) 16 { 17 s64 *constraint_ns_p = data; 18 s64 constraint_ns; 19 20 if (dev->power.subsys_data && dev->power.subsys_data->domain_data) { 21 /* 22 * Only take suspend-time QoS constraints of devices into 23 * account, because constraints updated after the device has 24 * been suspended are not guaranteed to be taken into account 25 * anyway. In order for them to take effect, the device has to 26 * be resumed and suspended again. 27 */ 28 constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns; 29 } else { 30 /* 31 * The child is not in a domain and there's no info on its 32 * suspend/resume latencies, so assume them to be negligible and 33 * take its current PM QoS constraint (that's the only thing 34 * known at this point anyway). 35 */ 36 constraint_ns = dev_pm_qos_read_value(dev, DEV_PM_QOS_RESUME_LATENCY); 37 constraint_ns *= NSEC_PER_USEC; 38 } 39 40 if (constraint_ns < *constraint_ns_p) 41 *constraint_ns_p = constraint_ns; 42 43 return 0; 44 } 45 46 /** 47 * default_suspend_ok - Default PM domain governor routine to suspend devices. 48 * @dev: Device to check. 49 */ 50 static bool default_suspend_ok(struct device *dev) 51 { 52 struct gpd_timing_data *td = &dev_gpd_data(dev)->td; 53 unsigned long flags; 54 s64 constraint_ns; 55 56 dev_dbg(dev, "%s()\n", __func__); 57 58 spin_lock_irqsave(&dev->power.lock, flags); 59 60 if (!td->constraint_changed) { 61 bool ret = td->cached_suspend_ok; 62 63 spin_unlock_irqrestore(&dev->power.lock, flags); 64 return ret; 65 } 66 td->constraint_changed = false; 67 td->cached_suspend_ok = false; 68 td->effective_constraint_ns = 0; 69 constraint_ns = __dev_pm_qos_resume_latency(dev); 70 71 spin_unlock_irqrestore(&dev->power.lock, flags); 72 73 if (constraint_ns == 0) 74 return false; 75 76 constraint_ns *= NSEC_PER_USEC; 77 /* 78 * We can walk the children without any additional locking, because 79 * they all have been suspended at this point and their 80 * effective_constraint_ns fields won't be modified in parallel with us. 81 */ 82 if (!dev->power.ignore_children) 83 device_for_each_child(dev, &constraint_ns, 84 dev_update_qos_constraint); 85 86 if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS) { 87 /* "No restriction", so the device is allowed to suspend. */ 88 td->effective_constraint_ns = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS; 89 td->cached_suspend_ok = true; 90 } else if (constraint_ns == 0) { 91 /* 92 * This triggers if one of the children that don't belong to a 93 * domain has a zero PM QoS constraint and it's better not to 94 * suspend then. effective_constraint_ns is zero already and 95 * cached_suspend_ok is false, so bail out. 96 */ 97 return false; 98 } else { 99 constraint_ns -= td->suspend_latency_ns + 100 td->resume_latency_ns; 101 /* 102 * effective_constraint_ns is zero already and cached_suspend_ok 103 * is false, so if the computed value is not positive, return 104 * right away. 105 */ 106 if (constraint_ns <= 0) 107 return false; 108 109 td->effective_constraint_ns = constraint_ns; 110 td->cached_suspend_ok = true; 111 } 112 113 /* 114 * The children have been suspended already, so we don't need to take 115 * their suspend latencies into account here. 116 */ 117 return td->cached_suspend_ok; 118 } 119 120 static bool __default_power_down_ok(struct dev_pm_domain *pd, 121 unsigned int state) 122 { 123 struct generic_pm_domain *genpd = pd_to_genpd(pd); 124 struct gpd_link *link; 125 struct pm_domain_data *pdd; 126 s64 min_off_time_ns; 127 s64 off_on_time_ns; 128 129 off_on_time_ns = genpd->states[state].power_off_latency_ns + 130 genpd->states[state].power_on_latency_ns; 131 132 min_off_time_ns = -1; 133 /* 134 * Check if subdomains can be off for enough time. 135 * 136 * All subdomains have been powered off already at this point. 137 */ 138 list_for_each_entry(link, &genpd->parent_links, parent_node) { 139 struct generic_pm_domain *sd = link->child; 140 s64 sd_max_off_ns = sd->max_off_time_ns; 141 142 if (sd_max_off_ns < 0) 143 continue; 144 145 /* 146 * Check if the subdomain is allowed to be off long enough for 147 * the current domain to turn off and on (that's how much time 148 * it will have to wait worst case). 149 */ 150 if (sd_max_off_ns <= off_on_time_ns) 151 return false; 152 153 if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0) 154 min_off_time_ns = sd_max_off_ns; 155 } 156 157 /* 158 * Check if the devices in the domain can be off enough time. 159 */ 160 list_for_each_entry(pdd, &genpd->dev_list, list_node) { 161 struct gpd_timing_data *td; 162 s64 constraint_ns; 163 164 /* 165 * Check if the device is allowed to be off long enough for the 166 * domain to turn off and on (that's how much time it will 167 * have to wait worst case). 168 */ 169 td = &to_gpd_data(pdd)->td; 170 constraint_ns = td->effective_constraint_ns; 171 /* 172 * Zero means "no suspend at all" and this runs only when all 173 * devices in the domain are suspended, so it must be positive. 174 */ 175 if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS) 176 continue; 177 178 if (constraint_ns <= off_on_time_ns) 179 return false; 180 181 if (min_off_time_ns > constraint_ns || min_off_time_ns < 0) 182 min_off_time_ns = constraint_ns; 183 } 184 185 /* 186 * If the computed minimum device off time is negative, there are no 187 * latency constraints, so the domain can spend arbitrary time in the 188 * "off" state. 189 */ 190 if (min_off_time_ns < 0) 191 return true; 192 193 /* 194 * The difference between the computed minimum subdomain or device off 195 * time and the time needed to turn the domain on is the maximum 196 * theoretical time this domain can spend in the "off" state. 197 */ 198 genpd->max_off_time_ns = min_off_time_ns - 199 genpd->states[state].power_on_latency_ns; 200 return true; 201 } 202 203 /** 204 * default_power_down_ok - Default generic PM domain power off governor routine. 205 * @pd: PM domain to check. 206 * 207 * This routine must be executed under the PM domain's lock. 208 */ 209 static bool default_power_down_ok(struct dev_pm_domain *pd) 210 { 211 struct generic_pm_domain *genpd = pd_to_genpd(pd); 212 struct gpd_link *link; 213 214 if (!genpd->max_off_time_changed) { 215 genpd->state_idx = genpd->cached_power_down_state_idx; 216 return genpd->cached_power_down_ok; 217 } 218 219 /* 220 * We have to invalidate the cached results for the parents, so 221 * use the observation that default_power_down_ok() is not 222 * going to be called for any parent until this instance 223 * returns. 224 */ 225 list_for_each_entry(link, &genpd->child_links, child_node) 226 link->parent->max_off_time_changed = true; 227 228 genpd->max_off_time_ns = -1; 229 genpd->max_off_time_changed = false; 230 genpd->cached_power_down_ok = true; 231 genpd->state_idx = genpd->state_count - 1; 232 233 /* Find a state to power down to, starting from the deepest. */ 234 while (!__default_power_down_ok(pd, genpd->state_idx)) { 235 if (genpd->state_idx == 0) { 236 genpd->cached_power_down_ok = false; 237 break; 238 } 239 genpd->state_idx--; 240 } 241 242 genpd->cached_power_down_state_idx = genpd->state_idx; 243 return genpd->cached_power_down_ok; 244 } 245 246 static bool always_on_power_down_ok(struct dev_pm_domain *domain) 247 { 248 return false; 249 } 250 251 #ifdef CONFIG_CPU_IDLE 252 static bool cpu_power_down_ok(struct dev_pm_domain *pd) 253 { 254 struct generic_pm_domain *genpd = pd_to_genpd(pd); 255 struct cpuidle_device *dev; 256 ktime_t domain_wakeup, next_hrtimer; 257 s64 idle_duration_ns; 258 int cpu, i; 259 260 /* Validate dev PM QoS constraints. */ 261 if (!default_power_down_ok(pd)) 262 return false; 263 264 if (!(genpd->flags & GENPD_FLAG_CPU_DOMAIN)) 265 return true; 266 267 /* 268 * Find the next wakeup for any of the online CPUs within the PM domain 269 * and its subdomains. Note, we only need the genpd->cpus, as it already 270 * contains a mask of all CPUs from subdomains. 271 */ 272 domain_wakeup = ktime_set(KTIME_SEC_MAX, 0); 273 for_each_cpu_and(cpu, genpd->cpus, cpu_online_mask) { 274 dev = per_cpu(cpuidle_devices, cpu); 275 if (dev) { 276 next_hrtimer = READ_ONCE(dev->next_hrtimer); 277 if (ktime_before(next_hrtimer, domain_wakeup)) 278 domain_wakeup = next_hrtimer; 279 } 280 } 281 282 /* The minimum idle duration is from now - until the next wakeup. */ 283 idle_duration_ns = ktime_to_ns(ktime_sub(domain_wakeup, ktime_get())); 284 if (idle_duration_ns <= 0) 285 return false; 286 287 /* 288 * Find the deepest idle state that has its residency value satisfied 289 * and by also taking into account the power off latency for the state. 290 * Start at the state picked by the dev PM QoS constraint validation. 291 */ 292 i = genpd->state_idx; 293 do { 294 if (idle_duration_ns >= (genpd->states[i].residency_ns + 295 genpd->states[i].power_off_latency_ns)) { 296 genpd->state_idx = i; 297 return true; 298 } 299 } while (--i >= 0); 300 301 return false; 302 } 303 304 struct dev_power_governor pm_domain_cpu_gov = { 305 .suspend_ok = default_suspend_ok, 306 .power_down_ok = cpu_power_down_ok, 307 }; 308 #endif 309 310 struct dev_power_governor simple_qos_governor = { 311 .suspend_ok = default_suspend_ok, 312 .power_down_ok = default_power_down_ok, 313 }; 314 315 /** 316 * pm_genpd_gov_always_on - A governor implementing an always-on policy 317 */ 318 struct dev_power_governor pm_domain_always_on_gov = { 319 .power_down_ok = always_on_power_down_ok, 320 .suspend_ok = default_suspend_ok, 321 }; 322