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(rstc->shared)) 142 return -EINVAL; 143 144 if (rstc->rcdev->ops->reset) 145 return rstc->rcdev->ops->reset(rstc->rcdev, rstc->id); 146 147 return -ENOTSUPP; 148 } 149 EXPORT_SYMBOL_GPL(reset_control_reset); 150 151 /** 152 * reset_control_assert - asserts the reset line 153 * @rstc: reset controller 154 * 155 * Calling this on an exclusive reset controller guarantees that the reset 156 * will be asserted. When called on a shared reset controller the line may 157 * still be deasserted, as long as other users keep it so. 158 * 159 * For shared reset controls a driver cannot expect the hw's registers and 160 * internal state to be reset, but must be prepared for this to happen. 161 */ 162 int reset_control_assert(struct reset_control *rstc) 163 { 164 if (!rstc->rcdev->ops->assert) 165 return -ENOTSUPP; 166 167 if (rstc->shared) { 168 if (WARN_ON(atomic_read(&rstc->deassert_count) == 0)) 169 return -EINVAL; 170 171 if (atomic_dec_return(&rstc->deassert_count) != 0) 172 return 0; 173 } 174 175 return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id); 176 } 177 EXPORT_SYMBOL_GPL(reset_control_assert); 178 179 /** 180 * reset_control_deassert - deasserts the reset line 181 * @rstc: reset controller 182 * 183 * After calling this function, the reset is guaranteed to be deasserted. 184 */ 185 int reset_control_deassert(struct reset_control *rstc) 186 { 187 if (!rstc->rcdev->ops->deassert) 188 return -ENOTSUPP; 189 190 if (rstc->shared) { 191 if (atomic_inc_return(&rstc->deassert_count) != 1) 192 return 0; 193 } 194 195 return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->id); 196 } 197 EXPORT_SYMBOL_GPL(reset_control_deassert); 198 199 /** 200 * reset_control_status - returns a negative errno if not supported, a 201 * positive value if the reset line is asserted, or zero if the reset 202 * line is not asserted. 203 * @rstc: reset controller 204 */ 205 int reset_control_status(struct reset_control *rstc) 206 { 207 if (rstc->rcdev->ops->status) 208 return rstc->rcdev->ops->status(rstc->rcdev, rstc->id); 209 210 return -ENOTSUPP; 211 } 212 EXPORT_SYMBOL_GPL(reset_control_status); 213 214 static struct reset_control *__reset_control_get( 215 struct reset_controller_dev *rcdev, 216 unsigned int index, int shared) 217 { 218 struct reset_control *rstc; 219 220 lockdep_assert_held(&reset_list_mutex); 221 222 list_for_each_entry(rstc, &rcdev->reset_control_head, list) { 223 if (rstc->id == index) { 224 if (WARN_ON(!rstc->shared || !shared)) 225 return ERR_PTR(-EBUSY); 226 227 rstc->refcnt++; 228 return rstc; 229 } 230 } 231 232 rstc = kzalloc(sizeof(*rstc), GFP_KERNEL); 233 if (!rstc) 234 return ERR_PTR(-ENOMEM); 235 236 try_module_get(rcdev->owner); 237 238 rstc->rcdev = rcdev; 239 list_add(&rstc->list, &rcdev->reset_control_head); 240 rstc->id = index; 241 rstc->refcnt = 1; 242 rstc->shared = shared; 243 244 return rstc; 245 } 246 247 static void __reset_control_put(struct reset_control *rstc) 248 { 249 lockdep_assert_held(&reset_list_mutex); 250 251 if (--rstc->refcnt) 252 return; 253 254 module_put(rstc->rcdev->owner); 255 256 list_del(&rstc->list); 257 kfree(rstc); 258 } 259 260 struct reset_control *__of_reset_control_get(struct device_node *node, 261 const char *id, int index, int shared) 262 { 263 struct reset_control *rstc; 264 struct reset_controller_dev *r, *rcdev; 265 struct of_phandle_args args; 266 int rstc_id; 267 int ret; 268 269 if (!node) 270 return ERR_PTR(-EINVAL); 271 272 if (id) { 273 index = of_property_match_string(node, 274 "reset-names", id); 275 if (index < 0) 276 return ERR_PTR(-ENOENT); 277 } 278 279 ret = of_parse_phandle_with_args(node, "resets", "#reset-cells", 280 index, &args); 281 if (ret) 282 return ERR_PTR(ret); 283 284 mutex_lock(&reset_list_mutex); 285 rcdev = NULL; 286 list_for_each_entry(r, &reset_controller_list, list) { 287 if (args.np == r->of_node) { 288 rcdev = r; 289 break; 290 } 291 } 292 of_node_put(args.np); 293 294 if (!rcdev) { 295 mutex_unlock(&reset_list_mutex); 296 return ERR_PTR(-EPROBE_DEFER); 297 } 298 299 if (WARN_ON(args.args_count != rcdev->of_reset_n_cells)) { 300 mutex_unlock(&reset_list_mutex); 301 return ERR_PTR(-EINVAL); 302 } 303 304 rstc_id = rcdev->of_xlate(rcdev, &args); 305 if (rstc_id < 0) { 306 mutex_unlock(&reset_list_mutex); 307 return ERR_PTR(rstc_id); 308 } 309 310 /* reset_list_mutex also protects the rcdev's reset_control list */ 311 rstc = __reset_control_get(rcdev, rstc_id, shared); 312 313 mutex_unlock(&reset_list_mutex); 314 315 return rstc; 316 } 317 EXPORT_SYMBOL_GPL(__of_reset_control_get); 318 319 /** 320 * reset_control_put - free the reset controller 321 * @rstc: reset controller 322 */ 323 324 void reset_control_put(struct reset_control *rstc) 325 { 326 if (IS_ERR(rstc)) 327 return; 328 329 mutex_lock(&reset_list_mutex); 330 __reset_control_put(rstc); 331 mutex_unlock(&reset_list_mutex); 332 } 333 EXPORT_SYMBOL_GPL(reset_control_put); 334 335 static void devm_reset_control_release(struct device *dev, void *res) 336 { 337 reset_control_put(*(struct reset_control **)res); 338 } 339 340 struct reset_control *__devm_reset_control_get(struct device *dev, 341 const char *id, int index, int shared) 342 { 343 struct reset_control **ptr, *rstc; 344 345 ptr = devres_alloc(devm_reset_control_release, sizeof(*ptr), 346 GFP_KERNEL); 347 if (!ptr) 348 return ERR_PTR(-ENOMEM); 349 350 rstc = __of_reset_control_get(dev ? dev->of_node : NULL, 351 id, index, shared); 352 if (!IS_ERR(rstc)) { 353 *ptr = rstc; 354 devres_add(dev, ptr); 355 } else { 356 devres_free(ptr); 357 } 358 359 return rstc; 360 } 361 EXPORT_SYMBOL_GPL(__devm_reset_control_get); 362 363 /** 364 * device_reset - find reset controller associated with the device 365 * and perform reset 366 * @dev: device to be reset by the controller 367 * 368 * Convenience wrapper for reset_control_get() and reset_control_reset(). 369 * This is useful for the common case of devices with single, dedicated reset 370 * lines. 371 */ 372 int device_reset(struct device *dev) 373 { 374 struct reset_control *rstc; 375 int ret; 376 377 rstc = reset_control_get(dev, NULL); 378 if (IS_ERR(rstc)) 379 return PTR_ERR(rstc); 380 381 ret = reset_control_reset(rstc); 382 383 reset_control_put(rstc); 384 385 return ret; 386 } 387 EXPORT_SYMBOL_GPL(device_reset); 388