1 /* 2 * Reset Controller framework 3 * 4 * Copyright 2013 Philipp Zabel, Pengutronix 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License as published by 8 * the Free Software Foundation; either version 2 of the License, or 9 * (at your option) any later version. 10 */ 11 #include <linux/atomic.h> 12 #include <linux/device.h> 13 #include <linux/err.h> 14 #include <linux/export.h> 15 #include <linux/kernel.h> 16 #include <linux/module.h> 17 #include <linux/of.h> 18 #include <linux/reset.h> 19 #include <linux/reset-controller.h> 20 #include <linux/slab.h> 21 22 static DEFINE_MUTEX(reset_list_mutex); 23 static LIST_HEAD(reset_controller_list); 24 25 /** 26 * struct reset_control - a reset control 27 * @rcdev: a pointer to the reset controller device 28 * this reset control belongs to 29 * @list: list entry for the rcdev's reset controller list 30 * @id: ID of the reset controller in the reset 31 * controller device 32 * @refcnt: Number of gets of this reset_control 33 * @shared: Is this a shared (1), or an exclusive (0) reset_control? 34 * @deassert_cnt: Number of times this reset line has been deasserted 35 * @triggered_count: Number of times this reset line has been reset. Currently 36 * only used for shared resets, which means that the value 37 * will be either 0 or 1. 38 */ 39 struct reset_control { 40 struct reset_controller_dev *rcdev; 41 struct list_head list; 42 unsigned int id; 43 unsigned int refcnt; 44 int shared; 45 atomic_t deassert_count; 46 atomic_t triggered_count; 47 }; 48 49 /** 50 * of_reset_simple_xlate - translate reset_spec to the reset line number 51 * @rcdev: a pointer to the reset controller device 52 * @reset_spec: reset line specifier as found in the device tree 53 * @flags: a flags pointer to fill in (optional) 54 * 55 * This simple translation function should be used for reset controllers 56 * with 1:1 mapping, where reset lines can be indexed by number without gaps. 57 */ 58 static int of_reset_simple_xlate(struct reset_controller_dev *rcdev, 59 const struct of_phandle_args *reset_spec) 60 { 61 if (reset_spec->args[0] >= rcdev->nr_resets) 62 return -EINVAL; 63 64 return reset_spec->args[0]; 65 } 66 67 /** 68 * reset_controller_register - register a reset controller device 69 * @rcdev: a pointer to the initialized reset controller device 70 */ 71 int reset_controller_register(struct reset_controller_dev *rcdev) 72 { 73 if (!rcdev->of_xlate) { 74 rcdev->of_reset_n_cells = 1; 75 rcdev->of_xlate = of_reset_simple_xlate; 76 } 77 78 INIT_LIST_HEAD(&rcdev->reset_control_head); 79 80 mutex_lock(&reset_list_mutex); 81 list_add(&rcdev->list, &reset_controller_list); 82 mutex_unlock(&reset_list_mutex); 83 84 return 0; 85 } 86 EXPORT_SYMBOL_GPL(reset_controller_register); 87 88 /** 89 * reset_controller_unregister - unregister a reset controller device 90 * @rcdev: a pointer to the reset controller device 91 */ 92 void reset_controller_unregister(struct reset_controller_dev *rcdev) 93 { 94 mutex_lock(&reset_list_mutex); 95 list_del(&rcdev->list); 96 mutex_unlock(&reset_list_mutex); 97 } 98 EXPORT_SYMBOL_GPL(reset_controller_unregister); 99 100 static void devm_reset_controller_release(struct device *dev, void *res) 101 { 102 reset_controller_unregister(*(struct reset_controller_dev **)res); 103 } 104 105 /** 106 * devm_reset_controller_register - resource managed reset_controller_register() 107 * @dev: device that is registering this reset controller 108 * @rcdev: a pointer to the initialized reset controller device 109 * 110 * Managed reset_controller_register(). For reset controllers registered by 111 * this function, reset_controller_unregister() is automatically called on 112 * driver detach. See reset_controller_register() for more information. 113 */ 114 int devm_reset_controller_register(struct device *dev, 115 struct reset_controller_dev *rcdev) 116 { 117 struct reset_controller_dev **rcdevp; 118 int ret; 119 120 rcdevp = devres_alloc(devm_reset_controller_release, sizeof(*rcdevp), 121 GFP_KERNEL); 122 if (!rcdevp) 123 return -ENOMEM; 124 125 ret = reset_controller_register(rcdev); 126 if (!ret) { 127 *rcdevp = rcdev; 128 devres_add(dev, rcdevp); 129 } else { 130 devres_free(rcdevp); 131 } 132 133 return ret; 134 } 135 EXPORT_SYMBOL_GPL(devm_reset_controller_register); 136 137 /** 138 * reset_control_reset - reset the controlled device 139 * @rstc: reset controller 140 * 141 * On a shared reset line the actual reset pulse is only triggered once for the 142 * lifetime of the reset_control instance: for all but the first caller this is 143 * a no-op. 144 * Consumers must not use reset_control_(de)assert on shared reset lines when 145 * reset_control_reset has been used. 146 */ 147 int reset_control_reset(struct reset_control *rstc) 148 { 149 int ret; 150 151 if (WARN_ON(IS_ERR_OR_NULL(rstc))) 152 return -EINVAL; 153 154 if (!rstc->rcdev->ops->reset) 155 return -ENOTSUPP; 156 157 if (rstc->shared) { 158 if (WARN_ON(atomic_read(&rstc->deassert_count) != 0)) 159 return -EINVAL; 160 161 if (atomic_inc_return(&rstc->triggered_count) != 1) 162 return 0; 163 } 164 165 ret = rstc->rcdev->ops->reset(rstc->rcdev, rstc->id); 166 if (rstc->shared && !ret) 167 atomic_dec(&rstc->triggered_count); 168 169 return ret; 170 } 171 EXPORT_SYMBOL_GPL(reset_control_reset); 172 173 /** 174 * reset_control_assert - asserts the reset line 175 * @rstc: reset controller 176 * 177 * Calling this on an exclusive reset controller guarantees that the reset 178 * will be asserted. When called on a shared reset controller the line may 179 * still be deasserted, as long as other users keep it so. 180 * 181 * For shared reset controls a driver cannot expect the hw's registers and 182 * internal state to be reset, but must be prepared for this to happen. 183 * Consumers must not use reset_control_reset on shared reset lines when 184 * reset_control_(de)assert has been used. 185 */ 186 int reset_control_assert(struct reset_control *rstc) 187 { 188 if (WARN_ON(IS_ERR_OR_NULL(rstc))) 189 return -EINVAL; 190 191 if (!rstc->rcdev->ops->assert) 192 return -ENOTSUPP; 193 194 if (rstc->shared) { 195 if (WARN_ON(atomic_read(&rstc->triggered_count) != 0)) 196 return -EINVAL; 197 198 if (WARN_ON(atomic_read(&rstc->deassert_count) == 0)) 199 return -EINVAL; 200 201 if (atomic_dec_return(&rstc->deassert_count) != 0) 202 return 0; 203 } 204 205 return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id); 206 } 207 EXPORT_SYMBOL_GPL(reset_control_assert); 208 209 /** 210 * reset_control_deassert - deasserts the reset line 211 * @rstc: reset controller 212 * 213 * After calling this function, the reset is guaranteed to be deasserted. 214 * Consumers must not use reset_control_reset on shared reset lines when 215 * reset_control_(de)assert has been used. 216 */ 217 int reset_control_deassert(struct reset_control *rstc) 218 { 219 if (WARN_ON(IS_ERR_OR_NULL(rstc))) 220 return -EINVAL; 221 222 if (!rstc->rcdev->ops->deassert) 223 return -ENOTSUPP; 224 225 if (rstc->shared) { 226 if (WARN_ON(atomic_read(&rstc->triggered_count) != 0)) 227 return -EINVAL; 228 229 if (atomic_inc_return(&rstc->deassert_count) != 1) 230 return 0; 231 } 232 233 return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->id); 234 } 235 EXPORT_SYMBOL_GPL(reset_control_deassert); 236 237 /** 238 * reset_control_status - returns a negative errno if not supported, a 239 * positive value if the reset line is asserted, or zero if the reset 240 * line is not asserted. 241 * @rstc: reset controller 242 */ 243 int reset_control_status(struct reset_control *rstc) 244 { 245 if (WARN_ON(IS_ERR_OR_NULL(rstc))) 246 return -EINVAL; 247 248 if (rstc->rcdev->ops->status) 249 return rstc->rcdev->ops->status(rstc->rcdev, rstc->id); 250 251 return -ENOTSUPP; 252 } 253 EXPORT_SYMBOL_GPL(reset_control_status); 254 255 static struct reset_control *__reset_control_get( 256 struct reset_controller_dev *rcdev, 257 unsigned int index, int shared) 258 { 259 struct reset_control *rstc; 260 261 lockdep_assert_held(&reset_list_mutex); 262 263 list_for_each_entry(rstc, &rcdev->reset_control_head, list) { 264 if (rstc->id == index) { 265 if (WARN_ON(!rstc->shared || !shared)) 266 return ERR_PTR(-EBUSY); 267 268 rstc->refcnt++; 269 return rstc; 270 } 271 } 272 273 rstc = kzalloc(sizeof(*rstc), GFP_KERNEL); 274 if (!rstc) 275 return ERR_PTR(-ENOMEM); 276 277 try_module_get(rcdev->owner); 278 279 rstc->rcdev = rcdev; 280 list_add(&rstc->list, &rcdev->reset_control_head); 281 rstc->id = index; 282 rstc->refcnt = 1; 283 rstc->shared = shared; 284 285 return rstc; 286 } 287 288 static void __reset_control_put(struct reset_control *rstc) 289 { 290 lockdep_assert_held(&reset_list_mutex); 291 292 if (--rstc->refcnt) 293 return; 294 295 module_put(rstc->rcdev->owner); 296 297 list_del(&rstc->list); 298 kfree(rstc); 299 } 300 301 struct reset_control *__of_reset_control_get(struct device_node *node, 302 const char *id, int index, int shared) 303 { 304 struct reset_control *rstc; 305 struct reset_controller_dev *r, *rcdev; 306 struct of_phandle_args args; 307 int rstc_id; 308 int ret; 309 310 if (!node) 311 return ERR_PTR(-EINVAL); 312 313 if (id) { 314 index = of_property_match_string(node, 315 "reset-names", id); 316 if (index < 0) 317 return ERR_PTR(-ENOENT); 318 } 319 320 ret = of_parse_phandle_with_args(node, "resets", "#reset-cells", 321 index, &args); 322 if (ret) 323 return ERR_PTR(ret); 324 325 mutex_lock(&reset_list_mutex); 326 rcdev = NULL; 327 list_for_each_entry(r, &reset_controller_list, list) { 328 if (args.np == r->of_node) { 329 rcdev = r; 330 break; 331 } 332 } 333 of_node_put(args.np); 334 335 if (!rcdev) { 336 mutex_unlock(&reset_list_mutex); 337 return ERR_PTR(-EPROBE_DEFER); 338 } 339 340 if (WARN_ON(args.args_count != rcdev->of_reset_n_cells)) { 341 mutex_unlock(&reset_list_mutex); 342 return ERR_PTR(-EINVAL); 343 } 344 345 rstc_id = rcdev->of_xlate(rcdev, &args); 346 if (rstc_id < 0) { 347 mutex_unlock(&reset_list_mutex); 348 return ERR_PTR(rstc_id); 349 } 350 351 /* reset_list_mutex also protects the rcdev's reset_control list */ 352 rstc = __reset_control_get(rcdev, rstc_id, shared); 353 354 mutex_unlock(&reset_list_mutex); 355 356 return rstc; 357 } 358 EXPORT_SYMBOL_GPL(__of_reset_control_get); 359 360 /** 361 * reset_control_put - free the reset controller 362 * @rstc: reset controller 363 */ 364 365 void reset_control_put(struct reset_control *rstc) 366 { 367 if (IS_ERR(rstc)) 368 return; 369 370 mutex_lock(&reset_list_mutex); 371 __reset_control_put(rstc); 372 mutex_unlock(&reset_list_mutex); 373 } 374 EXPORT_SYMBOL_GPL(reset_control_put); 375 376 static void devm_reset_control_release(struct device *dev, void *res) 377 { 378 reset_control_put(*(struct reset_control **)res); 379 } 380 381 struct reset_control *__devm_reset_control_get(struct device *dev, 382 const char *id, int index, int shared) 383 { 384 struct reset_control **ptr, *rstc; 385 386 ptr = devres_alloc(devm_reset_control_release, sizeof(*ptr), 387 GFP_KERNEL); 388 if (!ptr) 389 return ERR_PTR(-ENOMEM); 390 391 rstc = __of_reset_control_get(dev ? dev->of_node : NULL, 392 id, index, shared); 393 if (!IS_ERR(rstc)) { 394 *ptr = rstc; 395 devres_add(dev, ptr); 396 } else { 397 devres_free(ptr); 398 } 399 400 return rstc; 401 } 402 EXPORT_SYMBOL_GPL(__devm_reset_control_get); 403 404 /** 405 * device_reset - find reset controller associated with the device 406 * and perform reset 407 * @dev: device to be reset by the controller 408 * 409 * Convenience wrapper for reset_control_get() and reset_control_reset(). 410 * This is useful for the common case of devices with single, dedicated reset 411 * lines. 412 */ 413 int device_reset(struct device *dev) 414 { 415 struct reset_control *rstc; 416 int ret; 417 418 rstc = reset_control_get(dev, NULL); 419 if (IS_ERR(rstc)) 420 return PTR_ERR(rstc); 421 422 ret = reset_control_reset(rstc); 423 424 reset_control_put(rstc); 425 426 return ret; 427 } 428 EXPORT_SYMBOL_GPL(device_reset); 429