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  */
  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);