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(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);