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 /**
  97  * reset_control_reset - reset the controlled device
  98  * @rstc: reset controller
  99  *
 100  * Calling this on a shared reset controller is an error.
 101  */
 102 int reset_control_reset(struct reset_control *rstc)
 103 {
 104         if (WARN_ON(rstc->shared))
 105                 return -EINVAL;
 106
 107         if (rstc->rcdev->ops->reset)
 108                 return rstc->rcdev->ops->reset(rstc->rcdev, rstc->id);
 109
 110         return -ENOTSUPP;
 111 }
 112 EXPORT_SYMBOL_GPL(reset_control_reset);
 113
 114 /**
 115  * reset_control_assert - asserts the reset line
 116  * @rstc: reset controller
 117  *
 118  * Calling this on an exclusive reset controller guarantees that the reset
 119  * will be asserted. When called on a shared reset controller the line may
 120  * still be deasserted, as long as other users keep it so.
 121  *
 122  * For shared reset controls a driver cannot expect the hw's registers and
 123  * internal state to be reset, but must be prepared for this to happen.
 124  */
 125 int reset_control_assert(struct reset_control *rstc)
 126 {
 127         if (!rstc->rcdev->ops->assert)
 128                 return -ENOTSUPP;
 129
 130         if (rstc->shared) {
 131                 if (WARN_ON(atomic_read(&rstc->deassert_count) == 0))
 132                         return -EINVAL;
 133
 134                 if (atomic_dec_return(&rstc->deassert_count) != 0)
 135                         return 0;
 136         }
 137
 138         return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id);
 139 }
 140 EXPORT_SYMBOL_GPL(reset_control_assert);
 141
 142 /**
 143  * reset_control_deassert - deasserts the reset line
 144  * @rstc: reset controller
 145  *
 146  * After calling this function, the reset is guaranteed to be deasserted.
 147  */
 148 int reset_control_deassert(struct reset_control *rstc)
 149 {
 150         if (!rstc->rcdev->ops->deassert)
 151                 return -ENOTSUPP;
 152
 153         if (rstc->shared) {
 154                 if (atomic_inc_return(&rstc->deassert_count) != 1)
 155                         return 0;
 156         }
 157
 158         return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->id);
 159 }
 160 EXPORT_SYMBOL_GPL(reset_control_deassert);
 161
 162 /**
 163  * reset_control_status - returns a negative errno if not supported, a
 164  * positive value if the reset line is asserted, or zero if the reset
 165  * line is not asserted.
 166  * @rstc: reset controller
 167  */
 168 int reset_control_status(struct reset_control *rstc)
 169 {
 170         if (rstc->rcdev->ops->status)
 171                 return rstc->rcdev->ops->status(rstc->rcdev, rstc->id);
 172
 173         return -ENOTSUPP;
 174 }
 175 EXPORT_SYMBOL_GPL(reset_control_status);
 176
 177 static struct reset_control *__reset_control_get(
 178                                 struct reset_controller_dev *rcdev,
 179                                 unsigned int index, int shared)
 180 {
 181         struct reset_control *rstc;
 182
 183         lockdep_assert_held(&reset_list_mutex);
 184
 185         list_for_each_entry(rstc, &rcdev->reset_control_head, list) {
 186                 if (rstc->id == index) {
 187                         if (WARN_ON(!rstc->shared || !shared))
 188                                 return ERR_PTR(-EBUSY);
 189
 190                         rstc->refcnt++;
 191                         return rstc;
 192                 }
 193         }
 194
 195         rstc = kzalloc(sizeof(*rstc), GFP_KERNEL);
 196         if (!rstc)
 197                 return ERR_PTR(-ENOMEM);
 198
 199         try_module_get(rcdev->owner);
 200
 201         rstc->rcdev = rcdev;
 202         list_add(&rstc->list, &rcdev->reset_control_head);
 203         rstc->id = index;
 204         rstc->refcnt = 1;
 205         rstc->shared = shared;
 206
 207         return rstc;
 208 }
 209
 210 static void __reset_control_put(struct reset_control *rstc)
 211 {
 212         lockdep_assert_held(&reset_list_mutex);
 213
 214         if (--rstc->refcnt)
 215                 return;
 216
 217         module_put(rstc->rcdev->owner);
 218
 219         list_del(&rstc->list);
 220         kfree(rstc);
 221 }
 222
 223 struct reset_control *__of_reset_control_get(struct device_node *node,
 224                                      const char *id, int index, int shared)
 225 {
 226         struct reset_control *rstc;
 227         struct reset_controller_dev *r, *rcdev;
 228         struct of_phandle_args args;
 229         int rstc_id;
 230         int ret;
 231
 232         if (!node)
 233                 return ERR_PTR(-EINVAL);
 234
 235         if (id) {
 236                 index = of_property_match_string(node,
 237                                                  "reset-names", id);
 238                 if (index < 0)
 239                         return ERR_PTR(-ENOENT);
 240         }
 241
 242         ret = of_parse_phandle_with_args(node, "resets", "#reset-cells",
 243                                          index, &args);
 244         if (ret)
 245                 return ERR_PTR(ret);
 246
 247         mutex_lock(&reset_list_mutex);
 248         rcdev = NULL;
 249         list_for_each_entry(r, &reset_controller_list, list) {
 250                 if (args.np == r->of_node) {
 251                         rcdev = r;
 252                         break;
 253                 }
 254         }
 255         of_node_put(args.np);
 256
 257         if (!rcdev) {
 258                 mutex_unlock(&reset_list_mutex);
 259                 return ERR_PTR(-EPROBE_DEFER);
 260         }
 261
 262         if (WARN_ON(args.args_count != rcdev->of_reset_n_cells)) {
 263                 mutex_unlock(&reset_list_mutex);
 264                 return ERR_PTR(-EINVAL);
 265         }
 266
 267         rstc_id = rcdev->of_xlate(rcdev, &args);
 268         if (rstc_id < 0) {
 269                 mutex_unlock(&reset_list_mutex);
 270                 return ERR_PTR(rstc_id);
 271         }
 272
 273         /* reset_list_mutex also protects the rcdev's reset_control list */
 274         rstc = __reset_control_get(rcdev, rstc_id, shared);
 275
 276         mutex_unlock(&reset_list_mutex);
 277
 278         return rstc;
 279 }
 280 EXPORT_SYMBOL_GPL(__of_reset_control_get);
 281
 282 /**
 283  * reset_control_put - free the reset controller
 284  * @rstc: reset controller
 285  */
 286
 287 void reset_control_put(struct reset_control *rstc)
 288 {
 289         if (IS_ERR(rstc))
 290                 return;
 291
 292         mutex_lock(&reset_list_mutex);
 293         __reset_control_put(rstc);
 294         mutex_unlock(&reset_list_mutex);
 295 }
 296 EXPORT_SYMBOL_GPL(reset_control_put);
 297
 298 static void devm_reset_control_release(struct device *dev, void *res)
 299 {
 300         reset_control_put(*(struct reset_control **)res);
 301 }
 302
 303 struct reset_control *__devm_reset_control_get(struct device *dev,
 304                                      const char *id, int index, int shared)
 305 {
 306         struct reset_control **ptr, *rstc;
 307
 308         ptr = devres_alloc(devm_reset_control_release, sizeof(*ptr),
 309                            GFP_KERNEL);
 310         if (!ptr)
 311                 return ERR_PTR(-ENOMEM);
 312
 313         rstc = __of_reset_control_get(dev ? dev->of_node : NULL,
 314                                       id, index, shared);
 315         if (!IS_ERR(rstc)) {
 316                 *ptr = rstc;
 317                 devres_add(dev, ptr);
 318         } else {
 319                 devres_free(ptr);
 320         }
 321
 322         return rstc;
 323 }
 324 EXPORT_SYMBOL_GPL(__devm_reset_control_get);
 325
 326 /**
 327  * device_reset - find reset controller associated with the device
 328  *                and perform reset
 329  * @dev: device to be reset by the controller
 330  *
 331  * Convenience wrapper for reset_control_get() and reset_control_reset().
 332  * This is useful for the common case of devices with single, dedicated reset
 333  * lines.
 334  */
 335 int device_reset(struct device *dev)
 336 {
 337         struct reset_control *rstc;
 338         int ret;
 339
 340         rstc = reset_control_get(dev, NULL);
 341         if (IS_ERR(rstc))
 342                 return PTR_ERR(rstc);
 343
 344         ret = reset_control_reset(rstc);
 345
 346         reset_control_put(rstc);
 347
 348         return ret;
 349 }
 350 EXPORT_SYMBOL_GPL(device_reset);