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 fs_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 unsigned long power_res = em_scale_power(table[i].power); 161 162 table[i].cost = div64_u64(fmax * power_res, 163 table[i].frequency); 164 } 165 166 pd->table = table; 167 pd->nr_perf_states = nr_states; 168 169 return 0; 170 171 free_ps_table: 172 kfree(table); 173 return -EINVAL; 174 } 175 176 static int em_create_pd(struct device *dev, int nr_states, 177 struct em_data_callback *cb, cpumask_t *cpus) 178 { 179 struct em_perf_domain *pd; 180 struct device *cpu_dev; 181 int cpu, ret; 182 183 if (_is_cpu_device(dev)) { 184 pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL); 185 if (!pd) 186 return -ENOMEM; 187 188 cpumask_copy(em_span_cpus(pd), cpus); 189 } else { 190 pd = kzalloc(sizeof(*pd), GFP_KERNEL); 191 if (!pd) 192 return -ENOMEM; 193 } 194 195 ret = em_create_perf_table(dev, pd, nr_states, cb); 196 if (ret) { 197 kfree(pd); 198 return ret; 199 } 200 201 if (_is_cpu_device(dev)) 202 for_each_cpu(cpu, cpus) { 203 cpu_dev = get_cpu_device(cpu); 204 cpu_dev->em_pd = pd; 205 } 206 207 dev->em_pd = pd; 208 209 return 0; 210 } 211 212 /** 213 * em_pd_get() - Return the performance domain for a device 214 * @dev : Device to find the performance domain for 215 * 216 * Returns the performance domain to which @dev belongs, or NULL if it doesn't 217 * exist. 218 */ 219 struct em_perf_domain *em_pd_get(struct device *dev) 220 { 221 if (IS_ERR_OR_NULL(dev)) 222 return NULL; 223 224 return dev->em_pd; 225 } 226 EXPORT_SYMBOL_GPL(em_pd_get); 227 228 /** 229 * em_cpu_get() - Return the performance domain for a CPU 230 * @cpu : CPU to find the performance domain for 231 * 232 * Returns the performance domain to which @cpu belongs, or NULL if it doesn't 233 * exist. 234 */ 235 struct em_perf_domain *em_cpu_get(int cpu) 236 { 237 struct device *cpu_dev; 238 239 cpu_dev = get_cpu_device(cpu); 240 if (!cpu_dev) 241 return NULL; 242 243 return em_pd_get(cpu_dev); 244 } 245 EXPORT_SYMBOL_GPL(em_cpu_get); 246 247 /** 248 * em_dev_register_perf_domain() - Register the Energy Model (EM) for a device 249 * @dev : Device for which the EM is to register 250 * @nr_states : Number of performance states to register 251 * @cb : Callback functions providing the data of the Energy Model 252 * @cpus : Pointer to cpumask_t, which in case of a CPU device is 253 * obligatory. It can be taken from i.e. 'policy->cpus'. For other 254 * type of devices this should be set to NULL. 255 * 256 * Create Energy Model tables for a performance domain using the callbacks 257 * defined in cb. 258 * 259 * If multiple clients register the same performance domain, all but the first 260 * registration will be ignored. 261 * 262 * Return 0 on success 263 */ 264 int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states, 265 struct em_data_callback *cb, cpumask_t *cpus) 266 { 267 unsigned long cap, prev_cap = 0; 268 int cpu, ret; 269 270 if (!dev || !nr_states || !cb) 271 return -EINVAL; 272 273 /* 274 * Use a mutex to serialize the registration of performance domains and 275 * let the driver-defined callback functions sleep. 276 */ 277 mutex_lock(&em_pd_mutex); 278 279 if (dev->em_pd) { 280 ret = -EEXIST; 281 goto unlock; 282 } 283 284 if (_is_cpu_device(dev)) { 285 if (!cpus) { 286 dev_err(dev, "EM: invalid CPU mask\n"); 287 ret = -EINVAL; 288 goto unlock; 289 } 290 291 for_each_cpu(cpu, cpus) { 292 if (em_cpu_get(cpu)) { 293 dev_err(dev, "EM: exists for CPU%d\n", cpu); 294 ret = -EEXIST; 295 goto unlock; 296 } 297 /* 298 * All CPUs of a domain must have the same 299 * micro-architecture since they all share the same 300 * table. 301 */ 302 cap = arch_scale_cpu_capacity(cpu); 303 if (prev_cap && prev_cap != cap) { 304 dev_err(dev, "EM: CPUs of %*pbl must have the same capacity\n", 305 cpumask_pr_args(cpus)); 306 307 ret = -EINVAL; 308 goto unlock; 309 } 310 prev_cap = cap; 311 } 312 } 313 314 ret = em_create_pd(dev, nr_states, cb, cpus); 315 if (ret) 316 goto unlock; 317 318 em_debug_create_pd(dev); 319 dev_info(dev, "EM: created perf domain\n"); 320 321 unlock: 322 mutex_unlock(&em_pd_mutex); 323 return ret; 324 } 325 EXPORT_SYMBOL_GPL(em_dev_register_perf_domain); 326 327 /** 328 * em_dev_unregister_perf_domain() - Unregister Energy Model (EM) for a device 329 * @dev : Device for which the EM is registered 330 * 331 * Unregister the EM for the specified @dev (but not a CPU device). 332 */ 333 void em_dev_unregister_perf_domain(struct device *dev) 334 { 335 if (IS_ERR_OR_NULL(dev) || !dev->em_pd) 336 return; 337 338 if (_is_cpu_device(dev)) 339 return; 340 341 /* 342 * The mutex separates all register/unregister requests and protects 343 * from potential clean-up/setup issues in the debugfs directories. 344 * The debugfs directory name is the same as device's name. 345 */ 346 mutex_lock(&em_pd_mutex); 347 em_debug_remove_pd(dev); 348 349 kfree(dev->em_pd->table); 350 kfree(dev->em_pd); 351 dev->em_pd = NULL; 352 mutex_unlock(&em_pd_mutex); 353 } 354 EXPORT_SYMBOL_GPL(em_dev_unregister_perf_domain); 355