drivers/reset/core.c

   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         bool 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  * If rstc is NULL it is an optional reset and the function will just
 148  * return 0.
 149  */
 150 int reset_control_reset(struct reset_control *rstc)
 151 {
 152         int ret;
 153
 154         if (!rstc)
 155                 return 0;
 156
 157         if (WARN_ON(IS_ERR(rstc)))
 158                 return -EINVAL;
 159
 160         if (!rstc->rcdev->ops->reset)
 161                 return -ENOTSUPP;
 162
 163         if (rstc->shared) {
 164                 if (WARN_ON(atomic_read(&rstc->deassert_count) != 0))
 165                         return -EINVAL;
 166
 167                 if (atomic_inc_return(&rstc->triggered_count) != 1)
 168                         return 0;
 169         }
 170
 171         ret = rstc->rcdev->ops->reset(rstc->rcdev, rstc->id);
 172         if (rstc->shared && ret)
 173                 atomic_dec(&rstc->triggered_count);
 174
 175         return ret;
 176 }
 177 EXPORT_SYMBOL_GPL(reset_control_reset);
 178
 179 /**
 180  * reset_control_assert - asserts the reset line
 181  * @rstc: reset controller
 182  *
 183  * Calling this on an exclusive reset controller guarantees that the reset
 184  * will be asserted. When called on a shared reset controller the line may
 185  * still be deasserted, as long as other users keep it so.
 186  *
 187  * For shared reset controls a driver cannot expect the hw's registers and
 188  * internal state to be reset, but must be prepared for this to happen.
 189  * Consumers must not use reset_control_reset on shared reset lines when
 190  * reset_control_(de)assert has been used.
 191  * return 0.
 192  *
 193  * If rstc is NULL it is an optional reset and the function will just
 194  * return 0.
 195  */
 196 int reset_control_assert(struct reset_control *rstc)
 197 {
 198         if (!rstc)
 199                 return 0;
 200
 201         if (WARN_ON(IS_ERR(rstc)))
 202                 return -EINVAL;
 203
 204         if (!rstc->rcdev->ops->assert)
 205                 return -ENOTSUPP;
 206
 207         if (rstc->shared) {
 208                 if (WARN_ON(atomic_read(&rstc->triggered_count) != 0))
 209                         return -EINVAL;
 210
 211                 if (WARN_ON(atomic_read(&rstc->deassert_count) == 0))
 212                         return -EINVAL;
 213
 214                 if (atomic_dec_return(&rstc->deassert_count) != 0)
 215                         return 0;
 216         }
 217
 218         return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id);
 219 }
 220 EXPORT_SYMBOL_GPL(reset_control_assert);
 221
 222 /**
 223  * reset_control_deassert - deasserts the reset line
 224  * @rstc: reset controller
 225  *
 226  * After calling this function, the reset is guaranteed to be deasserted.
 227  * Consumers must not use reset_control_reset on shared reset lines when
 228  * reset_control_(de)assert has been used.
 229  * return 0.
 230  *
 231  * If rstc is NULL it is an optional reset and the function will just
 232  * return 0.
 233  */
 234 int reset_control_deassert(struct reset_control *rstc)
 235 {
 236         if (!rstc)
 237                 return 0;
 238
 239         if (WARN_ON(IS_ERR(rstc)))
 240                 return -EINVAL;
 241
 242         if (!rstc->rcdev->ops->deassert)
 243                 return -ENOTSUPP;
 244
 245         if (rstc->shared) {
 246                 if (WARN_ON(atomic_read(&rstc->triggered_count) != 0))
 247                         return -EINVAL;
 248
 249                 if (atomic_inc_return(&rstc->deassert_count) != 1)
 250                         return 0;
 251         }
 252
 253         return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->id);
 254 }
 255 EXPORT_SYMBOL_GPL(reset_control_deassert);
 256
 257 /**
 258  * reset_control_status - returns a negative errno if not supported, a
 259  * positive value if the reset line is asserted, or zero if the reset
 260  * line is not asserted or if the desc is NULL (optional reset).
 261  * @rstc: reset controller
 262  */
 263 int reset_control_status(struct reset_control *rstc)
 264 {
 265         if (!rstc)
 266                 return 0;
 267
 268         if (WARN_ON(IS_ERR(rstc)))
 269                 return -EINVAL;
 270
 271         if (rstc->rcdev->ops->status)
 272                 return rstc->rcdev->ops->status(rstc->rcdev, rstc->id);
 273
 274         return -ENOTSUPP;
 275 }
 276 EXPORT_SYMBOL_GPL(reset_control_status);
 277
 278 static struct reset_control *__reset_control_get_internal(
 279                                 struct reset_controller_dev *rcdev,
 280                                 unsigned int index, bool shared)
 281 {
 282         struct reset_control *rstc;
 283
 284         lockdep_assert_held(&reset_list_mutex);
 285
 286         list_for_each_entry(rstc, &rcdev->reset_control_head, list) {
 287                 if (rstc->id == index) {
 288                         if (WARN_ON(!rstc->shared || !shared))
 289                                 return ERR_PTR(-EBUSY);
 290
 291                         rstc->refcnt++;
 292                         return rstc;
 293                 }
 294         }
 295
 296         rstc = kzalloc(sizeof(*rstc), GFP_KERNEL);
 297         if (!rstc)
 298                 return ERR_PTR(-ENOMEM);
 299
 300         try_module_get(rcdev->owner);
 301
 302         rstc->rcdev = rcdev;
 303         list_add(&rstc->list, &rcdev->reset_control_head);
 304         rstc->id = index;
 305         rstc->refcnt = 1;
 306         rstc->shared = shared;
 307
 308         return rstc;
 309 }
 310
 311 static void __reset_control_put_internal(struct reset_control *rstc)
 312 {
 313         lockdep_assert_held(&reset_list_mutex);
 314
 315         if (--rstc->refcnt)
 316                 return;
 317
 318         module_put(rstc->rcdev->owner);
 319
 320         list_del(&rstc->list);
 321         kfree(rstc);
 322 }
 323
 324 struct reset_control *__of_reset_control_get(struct device_node *node,
 325                                      const char *id, int index, bool shared,
 326                                      bool optional)
 327 {
 328         struct reset_control *rstc;
 329         struct reset_controller_dev *r, *rcdev;
 330         struct of_phandle_args args;
 331         int rstc_id;
 332         int ret;
 333
 334         if (!node)
 335                 return ERR_PTR(-EINVAL);
 336
 337         if (id) {
 338                 index = of_property_match_string(node,
 339                                                  "reset-names", id);
 340                 if (index == -EILSEQ)
 341                         return ERR_PTR(index);
 342                 if (index < 0)
 343                         return optional ? NULL : ERR_PTR(-ENOENT);
 344         }
 345
 346         ret = of_parse_phandle_with_args(node, "resets", "#reset-cells",
 347                                          index, &args);
 348         if (ret == -EINVAL)
 349                 return ERR_PTR(ret);
 350         if (ret)
 351                 return optional ? NULL : ERR_PTR(ret);
 352
 353         mutex_lock(&reset_list_mutex);
 354         rcdev = NULL;
 355         list_for_each_entry(r, &reset_controller_list, list) {
 356                 if (args.np == r->of_node) {
 357                         rcdev = r;
 358                         break;
 359                 }
 360         }
 361         of_node_put(args.np);
 362
 363         if (!rcdev) {
 364                 mutex_unlock(&reset_list_mutex);
 365                 return ERR_PTR(-EPROBE_DEFER);
 366         }
 367
 368         if (WARN_ON(args.args_count != rcdev->of_reset_n_cells)) {
 369                 mutex_unlock(&reset_list_mutex);
 370                 return ERR_PTR(-EINVAL);
 371         }
 372
 373         rstc_id = rcdev->of_xlate(rcdev, &args);
 374         if (rstc_id < 0) {
 375                 mutex_unlock(&reset_list_mutex);
 376                 return ERR_PTR(rstc_id);
 377         }
 378
 379         /* reset_list_mutex also protects the rcdev's reset_control list */
 380         rstc = __reset_control_get_internal(rcdev, rstc_id, shared);
 381
 382         mutex_unlock(&reset_list_mutex);
 383
 384         return rstc;
 385 }
 386 EXPORT_SYMBOL_GPL(__of_reset_control_get);
 387
 388 struct reset_control *__reset_control_get(struct device *dev, const char *id,
 389                                           int index, bool shared, bool optional)
 390 {
 391         if (dev->of_node)
 392                 return __of_reset_control_get(dev->of_node, id, index, shared,
 393                                               optional);
 394
 395         return optional ? NULL : ERR_PTR(-EINVAL);
 396 }
 397 EXPORT_SYMBOL_GPL(__reset_control_get);
 398
 399 /**
 400  * reset_control_put - free the reset controller
 401  * @rstc: reset controller
 402  */
 403
 404 void reset_control_put(struct reset_control *rstc)
 405 {
 406         if (IS_ERR_OR_NULL(rstc))
 407                 return;
 408
 409         mutex_lock(&reset_list_mutex);
 410         __reset_control_put_internal(rstc);
 411         mutex_unlock(&reset_list_mutex);
 412 }
 413 EXPORT_SYMBOL_GPL(reset_control_put);
 414
 415 static void devm_reset_control_release(struct device *dev, void *res)
 416 {
 417         reset_control_put(*(struct reset_control **)res);
 418 }
 419
 420 struct reset_control *__devm_reset_control_get(struct device *dev,
 421                                      const char *id, int index, bool shared,
 422                                      bool optional)
 423 {
 424         struct reset_control **ptr, *rstc;
 425
 426         ptr = devres_alloc(devm_reset_control_release, sizeof(*ptr),
 427                            GFP_KERNEL);
 428         if (!ptr)
 429                 return ERR_PTR(-ENOMEM);
 430
 431         rstc = __reset_control_get(dev, id, index, shared, optional);
 432         if (!IS_ERR(rstc)) {
 433                 *ptr = rstc;
 434                 devres_add(dev, ptr);
 435         } else {
 436                 devres_free(ptr);
 437         }
 438
 439         return rstc;
 440 }
 441 EXPORT_SYMBOL_GPL(__devm_reset_control_get);
 442
 443 /**
 444  * device_reset - find reset controller associated with the device
 445  *                and perform reset
 446  * @dev: device to be reset by the controller
 447  *
 448  * Convenience wrapper for reset_control_get() and reset_control_reset().
 449  * This is useful for the common case of devices with single, dedicated reset
 450  * lines.
 451  */
 452 int device_reset(struct device *dev)
 453 {
 454         struct reset_control *rstc;
 455         int ret;
 456
 457         rstc = reset_control_get(dev, NULL);
 458         if (IS_ERR(rstc))
 459                 return PTR_ERR(rstc);
 460
 461         ret = reset_control_reset(rstc);
 462
 463         reset_control_put(rstc);
 464
 465         return ret;
 466 }
 467 EXPORT_SYMBOL_GPL(device_reset);