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 */ 36 struct reset_control { 37 struct reset_controller_dev *rcdev; 38 struct list_head list; 39 unsigned int id; 40 unsigned int refcnt; 41 int shared; 42 atomic_t deassert_count; 43 }; 44 45 /** 46 * of_reset_simple_xlate - translate reset_spec to the reset line number 47 * @rcdev: a pointer to the reset controller device 48 * @reset_spec: reset line specifier as found in the device tree 49 * @flags: a flags pointer to fill in (optional) 50 * 51 * This simple translation function should be used for reset controllers 52 * with 1:1 mapping, where reset lines can be indexed by number without gaps. 53 */ 54 static int of_reset_simple_xlate(struct reset_controller_dev *rcdev, 55 const struct of_phandle_args *reset_spec) 56 { 57 if (reset_spec->args[0] >= rcdev->nr_resets) 58 return -EINVAL; 59 60 return reset_spec->args[0]; 61 } 62 63 /** 64 * reset_controller_register - register a reset controller device 65 * @rcdev: a pointer to the initialized reset controller device 66 */ 67 int reset_controller_register(struct reset_controller_dev *rcdev) 68 { 69 if (!rcdev->of_xlate) { 70 rcdev->of_reset_n_cells = 1; 71 rcdev->of_xlate = of_reset_simple_xlate; 72 } 73 74 INIT_LIST_HEAD(&rcdev->reset_control_head); 75 76 mutex_lock(&reset_list_mutex); 77 list_add(&rcdev->list, &reset_controller_list); 78 mutex_unlock(&reset_list_mutex); 79 80 return 0; 81 } 82 EXPORT_SYMBOL_GPL(reset_controller_register); 83 84 /** 85 * reset_controller_unregister - unregister a reset controller device 86 * @rcdev: a pointer to the reset controller device 87 */ 88 void reset_controller_unregister(struct reset_controller_dev *rcdev) 89 { 90 mutex_lock(&reset_list_mutex); 91 list_del(&rcdev->list); 92 mutex_unlock(&reset_list_mutex); 93 } 94 EXPORT_SYMBOL_GPL(reset_controller_unregister); 95 96 static void devm_reset_controller_release(struct device *dev, void *res) 97 { 98 reset_controller_unregister(*(struct reset_controller_dev **)res); 99 } 100 101 /** 102 * devm_reset_controller_register - resource managed reset_controller_register() 103 * @dev: device that is registering this reset controller 104 * @rcdev: a pointer to the initialized reset controller device 105 * 106 * Managed reset_controller_register(). For reset controllers registered by 107 * this function, reset_controller_unregister() is automatically called on 108 * driver detach. See reset_controller_register() for more information. 109 */ 110 int devm_reset_controller_register(struct device *dev, 111 struct reset_controller_dev *rcdev) 112 { 113 struct reset_controller_dev **rcdevp; 114 int ret; 115 116 rcdevp = devres_alloc(devm_reset_controller_release, sizeof(*rcdevp), 117 GFP_KERNEL); 118 if (!rcdevp) 119 return -ENOMEM; 120 121 ret = reset_controller_register(rcdev); 122 if (!ret) { 123 *rcdevp = rcdev; 124 devres_add(dev, rcdevp); 125 } else { 126 devres_free(rcdevp); 127 } 128 129 return ret; 130 } 131 EXPORT_SYMBOL_GPL(devm_reset_controller_register); 132 133 /** 134 * reset_control_reset - reset the controlled device 135 * @rstc: reset controller 136 * 137 * Calling this on a shared reset controller is an error. 138 */ 139 int reset_control_reset(struct reset_control *rstc) 140 { 141 if (WARN_ON(IS_ERR_OR_NULL(rstc)) || 142 WARN_ON(rstc->shared)) 143 return -EINVAL; 144 145 if (rstc->rcdev->ops->reset) 146 return rstc->rcdev->ops->reset(rstc->rcdev, rstc->id); 147 148 return -ENOTSUPP; 149 } 150 EXPORT_SYMBOL_GPL(reset_control_reset); 151 152 /** 153 * reset_control_assert - asserts the reset line 154 * @rstc: reset controller 155 * 156 * Calling this on an exclusive reset controller guarantees that the reset 157 * will be asserted. When called on a shared reset controller the line may 158 * still be deasserted, as long as other users keep it so. 159 * 160 * For shared reset controls a driver cannot expect the hw's registers and 161 * internal state to be reset, but must be prepared for this to happen. 162 */ 163 int reset_control_assert(struct reset_control *rstc) 164 { 165 if (WARN_ON(IS_ERR_OR_NULL(rstc))) 166 return -EINVAL; 167 168 if (!rstc->rcdev->ops->assert) 169 return -ENOTSUPP; 170 171 if (rstc->shared) { 172 if (WARN_ON(atomic_read(&rstc->deassert_count) == 0)) 173 return -EINVAL; 174 175 if (atomic_dec_return(&rstc->deassert_count) != 0) 176 return 0; 177 } 178 179 return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id); 180 } 181 EXPORT_SYMBOL_GPL(reset_control_assert); 182 183 /** 184 * reset_control_deassert - deasserts the reset line 185 * @rstc: reset controller 186 * 187 * After calling this function, the reset is guaranteed to be deasserted. 188 */ 189 int reset_control_deassert(struct reset_control *rstc) 190 { 191 if (WARN_ON(IS_ERR_OR_NULL(rstc))) 192 return -EINVAL; 193 194 if (!rstc->rcdev->ops->deassert) 195 return -ENOTSUPP; 196 197 if (rstc->shared) { 198 if (atomic_inc_return(&rstc->deassert_count) != 1) 199 return 0; 200 } 201 202 return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->id); 203 } 204 EXPORT_SYMBOL_GPL(reset_control_deassert); 205 206 /** 207 * reset_control_status - returns a negative errno if not supported, a 208 * positive value if the reset line is asserted, or zero if the reset 209 * line is not asserted. 210 * @rstc: reset controller 211 */ 212 int reset_control_status(struct reset_control *rstc) 213 { 214 if (WARN_ON(IS_ERR_OR_NULL(rstc))) 215 return -EINVAL; 216 217 if (rstc->rcdev->ops->status) 218 return rstc->rcdev->ops->status(rstc->rcdev, rstc->id); 219 220 return -ENOTSUPP; 221 } 222 EXPORT_SYMBOL_GPL(reset_control_status); 223 224 static struct reset_control *__reset_control_get( 225 struct reset_controller_dev *rcdev, 226 unsigned int index, int shared) 227 { 228 struct reset_control *rstc; 229 230 lockdep_assert_held(&reset_list_mutex); 231 232 list_for_each_entry(rstc, &rcdev->reset_control_head, list) { 233 if (rstc->id == index) { 234 if (WARN_ON(!rstc->shared || !shared)) 235 return ERR_PTR(-EBUSY); 236 237 rstc->refcnt++; 238 return rstc; 239 } 240 } 241 242 rstc = kzalloc(sizeof(*rstc), GFP_KERNEL); 243 if (!rstc) 244 return ERR_PTR(-ENOMEM); 245 246 try_module_get(rcdev->owner); 247 248 rstc->rcdev = rcdev; 249 list_add(&rstc->list, &rcdev->reset_control_head); 250 rstc->id = index; 251 rstc->refcnt = 1; 252 rstc->shared = shared; 253 254 return rstc; 255 } 256 257 static void __reset_control_put(struct reset_control *rstc) 258 { 259 lockdep_assert_held(&reset_list_mutex); 260 261 if (--rstc->refcnt) 262 return; 263 264 module_put(rstc->rcdev->owner); 265 266 list_del(&rstc->list); 267 kfree(rstc); 268 } 269 270 struct reset_control *__of_reset_control_get(struct device_node *node, 271 const char *id, int index, int shared) 272 { 273 struct reset_control *rstc; 274 struct reset_controller_dev *r, *rcdev; 275 struct of_phandle_args args; 276 int rstc_id; 277 int ret; 278 279 if (!node) 280 return ERR_PTR(-EINVAL); 281 282 if (id) { 283 index = of_property_match_string(node, 284 "reset-names", id); 285 if (index < 0) 286 return ERR_PTR(-ENOENT); 287 } 288 289 ret = of_parse_phandle_with_args(node, "resets", "#reset-cells", 290 index, &args); 291 if (ret) 292 return ERR_PTR(ret); 293 294 mutex_lock(&reset_list_mutex); 295 rcdev = NULL; 296 list_for_each_entry(r, &reset_controller_list, list) { 297 if (args.np == r->of_node) { 298 rcdev = r; 299 break; 300 } 301 } 302 of_node_put(args.np); 303 304 if (!rcdev) { 305 mutex_unlock(&reset_list_mutex); 306 return ERR_PTR(-EPROBE_DEFER); 307 } 308 309 if (WARN_ON(args.args_count != rcdev->of_reset_n_cells)) { 310 mutex_unlock(&reset_list_mutex); 311 return ERR_PTR(-EINVAL); 312 } 313 314 rstc_id = rcdev->of_xlate(rcdev, &args); 315 if (rstc_id < 0) { 316 mutex_unlock(&reset_list_mutex); 317 return ERR_PTR(rstc_id); 318 } 319 320 /* reset_list_mutex also protects the rcdev's reset_control list */ 321 rstc = __reset_control_get(rcdev, rstc_id, shared); 322 323 mutex_unlock(&reset_list_mutex); 324 325 return rstc; 326 } 327 EXPORT_SYMBOL_GPL(__of_reset_control_get); 328 329 /** 330 * reset_control_put - free the reset controller 331 * @rstc: reset controller 332 */ 333 334 void reset_control_put(struct reset_control *rstc) 335 { 336 if (IS_ERR(rstc)) 337 return; 338 339 mutex_lock(&reset_list_mutex); 340 __reset_control_put(rstc); 341 mutex_unlock(&reset_list_mutex); 342 } 343 EXPORT_SYMBOL_GPL(reset_control_put); 344 345 static void devm_reset_control_release(struct device *dev, void *res) 346 { 347 reset_control_put(*(struct reset_control **)res); 348 } 349 350 struct reset_control *__devm_reset_control_get(struct device *dev, 351 const char *id, int index, int shared) 352 { 353 struct reset_control **ptr, *rstc; 354 355 ptr = devres_alloc(devm_reset_control_release, sizeof(*ptr), 356 GFP_KERNEL); 357 if (!ptr) 358 return ERR_PTR(-ENOMEM); 359 360 rstc = __of_reset_control_get(dev ? dev->of_node : NULL, 361 id, index, shared); 362 if (!IS_ERR(rstc)) { 363 *ptr = rstc; 364 devres_add(dev, ptr); 365 } else { 366 devres_free(ptr); 367 } 368 369 return rstc; 370 } 371 EXPORT_SYMBOL_GPL(__devm_reset_control_get); 372 373 /** 374 * device_reset - find reset controller associated with the device 375 * and perform reset 376 * @dev: device to be reset by the controller 377 * 378 * Convenience wrapper for reset_control_get() and reset_control_reset(). 379 * This is useful for the common case of devices with single, dedicated reset 380 * lines. 381 */ 382 int device_reset(struct device *dev) 383 { 384 struct reset_control *rstc; 385 int ret; 386 387 rstc = reset_control_get(dev, NULL); 388 if (IS_ERR(rstc)) 389 return PTR_ERR(rstc); 390 391 ret = reset_control_reset(rstc); 392 393 reset_control_put(rstc); 394 395 return ret; 396 } 397 EXPORT_SYMBOL_GPL(device_reset); 398