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); 351