1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Energy Model of devices 4 * 5 * Copyright (c) 2018-2020, Arm ltd. 6 * Written by: Quentin Perret, Arm ltd. 7 * Improvements provided by: Lukasz Luba, Arm ltd. 8 */ 9 10 #define pr_fmt(fmt) "energy_model: " fmt 11 12 #include <linux/cpu.h> 13 #include <linux/cpumask.h> 14 #include <linux/debugfs.h> 15 #include <linux/energy_model.h> 16 #include <linux/sched/topology.h> 17 #include <linux/slab.h> 18 19 /* 20 * Mutex serializing the registrations of performance domains and letting 21 * callbacks defined by drivers sleep. 22 */ 23 static DEFINE_MUTEX(em_pd_mutex); 24 25 static bool _is_cpu_device(struct device *dev) 26 { 27 return (dev->bus == &cpu_subsys); 28 } 29 30 #ifdef CONFIG_DEBUG_FS 31 static struct dentry *rootdir; 32 33 static void em_debug_create_ps(struct em_perf_state *ps, struct dentry *pd) 34 { 35 struct dentry *d; 36 char name[24]; 37 38 snprintf(name, sizeof(name), "ps:%lu", ps->frequency); 39 40 /* Create per-ps directory */ 41 d = debugfs_create_dir(name, pd); 42 debugfs_create_ulong("frequency", 0444, d, &ps->frequency); 43 debugfs_create_ulong("power", 0444, d, &ps->power); 44 debugfs_create_ulong("cost", 0444, d, &ps->cost); 45 } 46 47 static int em_debug_cpus_show(struct seq_file *s, void *unused) 48 { 49 seq_printf(s, "%*pbl\n", cpumask_pr_args(to_cpumask(s->private))); 50 51 return 0; 52 } 53 DEFINE_SHOW_ATTRIBUTE(em_debug_cpus); 54 55 static void em_debug_create_pd(struct device *dev) 56 { 57 struct dentry *d; 58 int i; 59 60 /* Create the directory of the performance domain */ 61 d = debugfs_create_dir(dev_name(dev), rootdir); 62 63 if (_is_cpu_device(dev)) 64 debugfs_create_file("cpus", 0444, d, dev->em_pd->cpus, 65 &em_debug_cpus_fops); 66 67 /* Create a sub-directory for each performance state */ 68 for (i = 0; i < dev->em_pd->nr_perf_states; i++) 69 em_debug_create_ps(&dev->em_pd->table[i], d); 70 71 } 72 73 static void em_debug_remove_pd(struct device *dev) 74 { 75 struct dentry *debug_dir; 76 77 debug_dir = debugfs_lookup(dev_name(dev), rootdir); 78 debugfs_remove_recursive(debug_dir); 79 } 80 81 static int __init em_debug_init(void) 82 { 83 /* Create /sys/kernel/debug/energy_model directory */ 84 rootdir = debugfs_create_dir("energy_model", NULL); 85 86 return 0; 87 } 88 core_initcall(em_debug_init); 89 #else /* CONFIG_DEBUG_FS */ 90 static void em_debug_create_pd(struct device *dev) {} 91 static void em_debug_remove_pd(struct device *dev) {} 92 #endif 93 94 static int em_create_perf_table(struct device *dev, struct em_perf_domain *pd, 95 int nr_states, struct em_data_callback *cb) 96 { 97 unsigned long opp_eff, prev_opp_eff = ULONG_MAX; 98 unsigned long power, freq, prev_freq = 0; 99 struct em_perf_state *table; 100 int i, ret; 101 u64 fmax; 102 103 table = kcalloc(nr_states, sizeof(*table), GFP_KERNEL); 104 if (!table) 105 return -ENOMEM; 106 107 /* Build the list of performance states for this performance domain */ 108 for (i = 0, freq = 0; i < nr_states; i++, freq++) { 109 /* 110 * active_power() is a driver callback which ceils 'freq' to 111 * lowest performance state of 'dev' above 'freq' and updates 112 * 'power' and 'freq' accordingly. 113 */ 114 ret = cb->active_power(&power, &freq, dev); 115 if (ret) { 116 dev_err(dev, "EM: invalid perf. state: %d\n", 117 ret); 118 goto free_ps_table; 119 } 120 121 /* 122 * We expect the driver callback to increase the frequency for 123 * higher performance states. 124 */ 125 if (freq <= prev_freq) { 126 dev_err(dev, "EM: non-increasing freq: %lu\n", 127 freq); 128 goto free_ps_table; 129 } 130 131 /* 132 * The power returned by active_state() is expected to be 133 * positive, in milli-watts and to fit into 16 bits. 134 */ 135 if (!power || power > EM_MAX_POWER) { 136 dev_err(dev, "EM: invalid power: %lu\n", 137 power); 138 goto free_ps_table; 139 } 140 141 table[i].power = power; 142 table[i].frequency = prev_freq = freq; 143 144 /* 145 * The hertz/watts efficiency ratio should decrease as the 146 * frequency grows on sane platforms. But this isn't always 147 * true in practice so warn the user if a higher OPP is more 148 * power efficient than a lower one. 149 */ 150 opp_eff = freq / power; 151 if (opp_eff >= prev_opp_eff) 152 dev_dbg(dev, "EM: hertz/watts ratio non-monotonically decreasing: em_perf_state %d >= em_perf_state%d\n", 153 i, i - 1); 154 prev_opp_eff = opp_eff; 155 } 156 157 /* Compute the cost of each performance state. */ 158 fmax = (u64) table[nr_states - 1].frequency; 159 for (i = 0; i < nr_states; i++) { 160 table[i].cost = div64_u64(fmax * table[i].power, 161 table[i].frequency); 162 } 163 164 pd->table = table; 165 pd->nr_perf_states = nr_states; 166 167 return 0; 168 169 free_ps_table: 170 kfree(table); 171 return -EINVAL; 172 } 173 174 static int em_create_pd(struct device *dev, int nr_states, 175 struct em_data_callback *cb, cpumask_t *cpus) 176 { 177 struct em_perf_domain *pd; 178 struct device *cpu_dev; 179 int cpu, ret; 180 181 if (_is_cpu_device(dev)) { 182 pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL); 183 if (!pd) 184 return -ENOMEM; 185 186 cpumask_copy(em_span_cpus(pd), cpus); 187 } else { 188 pd = kzalloc(sizeof(*pd), GFP_KERNEL); 189 if (!pd) 190 return -ENOMEM; 191 } 192 193 ret = em_create_perf_table(dev, pd, nr_states, cb); 194 if (ret) { 195 kfree(pd); 196 return ret; 197 } 198 199 if (_is_cpu_device(dev)) 200 for_each_cpu(cpu, cpus) { 201 cpu_dev = get_cpu_device(cpu); 202 cpu_dev->em_pd = pd; 203 } 204 205 dev->em_pd = pd; 206 207 return 0; 208 } 209 210 /** 211 * em_pd_get() - Return the performance domain for a device 212 * @dev : Device to find the performance domain for 213 * 214 * Returns the performance domain to which @dev belongs, or NULL if it doesn't 215 * exist. 216 */ 217 struct em_perf_domain *em_pd_get(struct device *dev) 218 { 219 if (IS_ERR_OR_NULL(dev)) 220 return NULL; 221 222 return dev->em_pd; 223 } 224 EXPORT_SYMBOL_GPL(em_pd_get); 225 226 /** 227 * em_cpu_get() - Return the performance domain for a CPU 228 * @cpu : CPU to find the performance domain for 229 * 230 * Returns the performance domain to which @cpu belongs, or NULL if it doesn't 231 * exist. 232 */ 233 struct em_perf_domain *em_cpu_get(int cpu) 234 { 235 struct device *cpu_dev; 236 237 cpu_dev = get_cpu_device(cpu); 238 if (!cpu_dev) 239 return NULL; 240 241 return em_pd_get(cpu_dev); 242 } 243 EXPORT_SYMBOL_GPL(em_cpu_get); 244 245 /** 246 * em_dev_register_perf_domain() - Register the Energy Model (EM) for a device 247 * @dev : Device for which the EM is to register 248 * @nr_states : Number of performance states to register 249 * @cb : Callback functions providing the data of the Energy Model 250 * @cpus : Pointer to cpumask_t, which in case of a CPU device is 251 * obligatory. It can be taken from i.e. 'policy->cpus'. For other 252 * type of devices this should be set to NULL. 253 * 254 * Create Energy Model tables for a performance domain using the callbacks 255 * defined in cb. 256 * 257 * If multiple clients register the same performance domain, all but the first 258 * registration will be ignored. 259 * 260 * Return 0 on success 261 */ 262 int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states, 263 struct em_data_callback *cb, cpumask_t *cpus) 264 { 265 unsigned long cap, prev_cap = 0; 266 int cpu, ret; 267 268 if (!dev || !nr_states || !cb) 269 return -EINVAL; 270 271 /* 272 * Use a mutex to serialize the registration of performance domains and 273 * let the driver-defined callback functions sleep. 274 */ 275 mutex_lock(&em_pd_mutex); 276 277 if (dev->em_pd) { 278 ret = -EEXIST; 279 goto unlock; 280 } 281 282 if (_is_cpu_device(dev)) { 283 if (!cpus) { 284 dev_err(dev, "EM: invalid CPU mask\n"); 285 ret = -EINVAL; 286 goto unlock; 287 } 288 289 for_each_cpu(cpu, cpus) { 290 if (em_cpu_get(cpu)) { 291 dev_err(dev, "EM: exists for CPU%d\n", cpu); 292 ret = -EEXIST; 293 goto unlock; 294 } 295 /* 296 * All CPUs of a domain must have the same 297 * micro-architecture since they all share the same 298 * table. 299 */ 300 cap = arch_scale_cpu_capacity(cpu); 301 if (prev_cap && prev_cap != cap) { 302 dev_err(dev, "EM: CPUs of %*pbl must have the same capacity\n", 303 cpumask_pr_args(cpus)); 304 305 ret = -EINVAL; 306 goto unlock; 307 } 308 prev_cap = cap; 309 } 310 } 311 312 ret = em_create_pd(dev, nr_states, cb, cpus); 313 if (ret) 314 goto unlock; 315 316 em_debug_create_pd(dev); 317 dev_info(dev, "EM: created perf domain\n"); 318 319 unlock: 320 mutex_unlock(&em_pd_mutex); 321 return ret; 322 } 323 EXPORT_SYMBOL_GPL(em_dev_register_perf_domain); 324 325 /** 326 * em_register_perf_domain() - Register the Energy Model of a performance domain 327 * @span : Mask of CPUs in the performance domain 328 * @nr_states : Number of capacity states to register 329 * @cb : Callback functions providing the data of the Energy Model 330 * 331 * Create Energy Model tables for a performance domain using the callbacks 332 * defined in cb. 333 * 334 * If multiple clients register the same performance domain, all but the first 335 * registration will be ignored. 336 * 337 * Return 0 on success 338 */ 339 int em_register_perf_domain(cpumask_t *span, unsigned int nr_states, 340 struct em_data_callback *cb) 341 { 342 struct device *cpu_dev; 343 344 cpu_dev = get_cpu_device(cpumask_first(span)); 345 346 return em_dev_register_perf_domain(cpu_dev, nr_states, cb, span); 347 } 348 EXPORT_SYMBOL_GPL(em_register_perf_domain); 349 350 /** 351 * em_dev_unregister_perf_domain() - Unregister Energy Model (EM) for a device 352 * @dev : Device for which the EM is registered 353 * 354 * Unregister the EM for the specified @dev (but not a CPU device). 355 */ 356 void em_dev_unregister_perf_domain(struct device *dev) 357 { 358 if (IS_ERR_OR_NULL(dev) || !dev->em_pd) 359 return; 360 361 if (_is_cpu_device(dev)) 362 return; 363 364 /* 365 * The mutex separates all register/unregister requests and protects 366 * from potential clean-up/setup issues in the debugfs directories. 367 * The debugfs directory name is the same as device's name. 368 */ 369 mutex_lock(&em_pd_mutex); 370 em_debug_remove_pd(dev); 371 372 kfree(dev->em_pd->table); 373 kfree(dev->em_pd); 374 dev->em_pd = NULL; 375 mutex_unlock(&em_pd_mutex); 376 } 377 EXPORT_SYMBOL_GPL(em_dev_unregister_perf_domain); 378