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         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);