drivers/firmware/arm_scmi/bus.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * System Control and Management Interface (SCMI) Message Protocol bus layer
   4  *
   5  * Copyright (C) 2018-2021 ARM Ltd.
   6  */
   7
   8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   9
  10 #include <linux/atomic.h>
  11 #include <linux/types.h>
  12 #include <linux/module.h>
  13 #include <linux/of.h>
  14 #include <linux/kernel.h>
  15 #include <linux/slab.h>
  16 #include <linux/device.h>
  17
  18 #include "common.h"
  19
  20 BLOCKING_NOTIFIER_HEAD(scmi_requested_devices_nh);
  21 EXPORT_SYMBOL_GPL(scmi_requested_devices_nh);
  22
  23 static DEFINE_IDA(scmi_bus_id);
  24
  25 static DEFINE_IDR(scmi_requested_devices);
  26 /* Protect access to scmi_requested_devices */
  27 static DEFINE_MUTEX(scmi_requested_devices_mtx);
  28
  29 struct scmi_requested_dev {
  30         const struct scmi_device_id *id_table;
  31         struct list_head node;
  32 };
  33
  34 /* Track globally the creation of SCMI SystemPower related devices */
  35 static atomic_t scmi_syspower_registered = ATOMIC_INIT(0);
  36
  37 /**
  38  * scmi_protocol_device_request  - Helper to request a device
  39  *
  40  * @id_table: A protocol/name pair descriptor for the device to be created.
  41  *
  42  * This helper let an SCMI driver request specific devices identified by the
  43  * @id_table to be created for each active SCMI instance.
  44  *
  45  * The requested device name MUST NOT be already existent for any protocol;
  46  * at first the freshly requested @id_table is annotated in the IDR table
  47  * @scmi_requested_devices and then the requested device is advertised to any
  48  * registered party via the @scmi_requested_devices_nh notification chain.
  49  *
  50  * Return: 0 on Success
  51  */
  52 static int scmi_protocol_device_request(const struct scmi_device_id *id_table)
  53 {
  54         int ret = 0;
  55         unsigned int id = 0;
  56         struct list_head *head, *phead = NULL;
  57         struct scmi_requested_dev *rdev;
  58
  59         pr_debug("Requesting SCMI device (%s) for protocol %x\n",
  60                  id_table->name, id_table->protocol_id);
  61
  62         if (IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT) &&
  63             !IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT_COEX)) {
  64                 pr_warn("SCMI Raw mode active. Rejecting '%s'/0x%02X\n",
  65                         id_table->name, id_table->protocol_id);
  66                 return -EINVAL;
  67         }
  68
  69         /*
  70          * Search for the matching protocol rdev list and then search
  71          * of any existent equally named device...fails if any duplicate found.
  72          */
  73         mutex_lock(&scmi_requested_devices_mtx);
  74         idr_for_each_entry(&scmi_requested_devices, head, id) {
  75                 if (!phead) {
  76                         /* A list found registered in the IDR is never empty */
  77                         rdev = list_first_entry(head, struct scmi_requested_dev,
  78                                                 node);
  79                         if (rdev->id_table->protocol_id ==
  80                             id_table->protocol_id)
  81                                 phead = head;
  82                 }
  83                 list_for_each_entry(rdev, head, node) {
  84                         if (!strcmp(rdev->id_table->name, id_table->name)) {
  85                                 pr_err("Ignoring duplicate request [%d] %s\n",
  86                                        rdev->id_table->protocol_id,
  87                                        rdev->id_table->name);
  88                                 ret = -EINVAL;
  89                                 goto out;
  90                         }
  91                 }
  92         }
  93
  94         /*
  95          * No duplicate found for requested id_table, so let's create a new
  96          * requested device entry for this new valid request.
  97          */
  98         rdev = kzalloc(sizeof(*rdev), GFP_KERNEL);
  99         if (!rdev) {
 100                 ret = -ENOMEM;
 101                 goto out;
 102         }
 103         rdev->id_table = id_table;
 104
 105         /*
 106          * Append the new requested device table descriptor to the head of the
 107          * related protocol list, eventually creating such head if not already
 108          * there.
 109          */
 110         if (!phead) {
 111                 phead = kzalloc(sizeof(*phead), GFP_KERNEL);
 112                 if (!phead) {
 113                         kfree(rdev);
 114                         ret = -ENOMEM;
 115                         goto out;
 116                 }
 117                 INIT_LIST_HEAD(phead);
 118
 119                 ret = idr_alloc(&scmi_requested_devices, (void *)phead,
 120                                 id_table->protocol_id,
 121                                 id_table->protocol_id + 1, GFP_KERNEL);
 122                 if (ret != id_table->protocol_id) {
 123                         pr_err("Failed to save SCMI device - ret:%d\n", ret);
 124                         kfree(rdev);
 125                         kfree(phead);
 126                         ret = -EINVAL;
 127                         goto out;
 128                 }
 129                 ret = 0;
 130         }
 131         list_add(&rdev->node, phead);
 132
 133 out:
 134         mutex_unlock(&scmi_requested_devices_mtx);
 135
 136         if (!ret)
 137                 blocking_notifier_call_chain(&scmi_requested_devices_nh,
 138                                              SCMI_BUS_NOTIFY_DEVICE_REQUEST,
 139                                              (void *)rdev->id_table);
 140
 141         return ret;
 142 }
 143
 144 /**
 145  * scmi_protocol_device_unrequest  - Helper to unrequest a device
 146  *
 147  * @id_table: A protocol/name pair descriptor for the device to be unrequested.
 148  *
 149  * The unrequested device, described by the provided id_table, is at first
 150  * removed from the IDR @scmi_requested_devices and then the removal is
 151  * advertised to any registered party via the @scmi_requested_devices_nh
 152  * notification chain.
 153  */
 154 static void scmi_protocol_device_unrequest(const struct scmi_device_id *id_table)
 155 {
 156         struct list_head *phead;
 157
 158         pr_debug("Unrequesting SCMI device (%s) for protocol %x\n",
 159                  id_table->name, id_table->protocol_id);
 160
 161         mutex_lock(&scmi_requested_devices_mtx);
 162         phead = idr_find(&scmi_requested_devices, id_table->protocol_id);
 163         if (phead) {
 164                 struct scmi_requested_dev *victim, *tmp;
 165
 166                 list_for_each_entry_safe(victim, tmp, phead, node) {
 167                         if (!strcmp(victim->id_table->name, id_table->name)) {
 168                                 list_del(&victim->node);
 169
 170                                 mutex_unlock(&scmi_requested_devices_mtx);
 171                                 blocking_notifier_call_chain(&scmi_requested_devices_nh,
 172                                                              SCMI_BUS_NOTIFY_DEVICE_UNREQUEST,
 173                                                              (void *)victim->id_table);
 174                                 kfree(victim);
 175                                 mutex_lock(&scmi_requested_devices_mtx);
 176                                 break;
 177                         }
 178                 }
 179
 180                 if (list_empty(phead)) {
 181                         idr_remove(&scmi_requested_devices,
 182                                    id_table->protocol_id);
 183                         kfree(phead);
 184                 }
 185         }
 186         mutex_unlock(&scmi_requested_devices_mtx);
 187 }
 188
 189 static const struct scmi_device_id *
 190 scmi_dev_match_id(struct scmi_device *scmi_dev, struct scmi_driver *scmi_drv)
 191 {
 192         const struct scmi_device_id *id = scmi_drv->id_table;
 193
 194         if (!id)
 195                 return NULL;
 196
 197         for (; id->protocol_id; id++)
 198                 if (id->protocol_id == scmi_dev->protocol_id) {
 199                         if (!id->name)
 200                                 return id;
 201                         else if (!strcmp(id->name, scmi_dev->name))
 202                                 return id;
 203                 }
 204
 205         return NULL;
 206 }
 207
 208 static int scmi_dev_match(struct device *dev, struct device_driver *drv)
 209 {
 210         struct scmi_driver *scmi_drv = to_scmi_driver(drv);
 211         struct scmi_device *scmi_dev = to_scmi_dev(dev);
 212         const struct scmi_device_id *id;
 213
 214         id = scmi_dev_match_id(scmi_dev, scmi_drv);
 215         if (id)
 216                 return 1;
 217
 218         return 0;
 219 }
 220
 221 static int scmi_match_by_id_table(struct device *dev, void *data)
 222 {
 223         struct scmi_device *sdev = to_scmi_dev(dev);
 224         struct scmi_device_id *id_table = data;
 225
 226         return sdev->protocol_id == id_table->protocol_id &&
 227                 (id_table->name && !strcmp(sdev->name, id_table->name));
 228 }
 229
 230 static struct scmi_device *scmi_child_dev_find(struct device *parent,
 231                                                int prot_id, const char *name)
 232 {
 233         struct scmi_device_id id_table;
 234         struct device *dev;
 235
 236         id_table.protocol_id = prot_id;
 237         id_table.name = name;
 238
 239         dev = device_find_child(parent, &id_table, scmi_match_by_id_table);
 240         if (!dev)
 241                 return NULL;
 242
 243         return to_scmi_dev(dev);
 244 }
 245
 246 static int scmi_dev_probe(struct device *dev)
 247 {
 248         struct scmi_driver *scmi_drv = to_scmi_driver(dev->driver);
 249         struct scmi_device *scmi_dev = to_scmi_dev(dev);
 250
 251         if (!scmi_dev->handle)
 252                 return -EPROBE_DEFER;
 253
 254         return scmi_drv->probe(scmi_dev);
 255 }
 256
 257 static void scmi_dev_remove(struct device *dev)
 258 {
 259         struct scmi_driver *scmi_drv = to_scmi_driver(dev->driver);
 260         struct scmi_device *scmi_dev = to_scmi_dev(dev);
 261
 262         if (scmi_drv->remove)
 263                 scmi_drv->remove(scmi_dev);
 264 }
 265
 266 struct bus_type scmi_bus_type = {
 267         .name = "scmi_protocol",
 268         .match = scmi_dev_match,
 269         .probe = scmi_dev_probe,
 270         .remove = scmi_dev_remove,
 271 };
 272 EXPORT_SYMBOL_GPL(scmi_bus_type);
 273
 274 int scmi_driver_register(struct scmi_driver *driver, struct module *owner,
 275                          const char *mod_name)
 276 {
 277         int retval;
 278
 279         if (!driver->probe)
 280                 return -EINVAL;
 281
 282         retval = scmi_protocol_device_request(driver->id_table);
 283         if (retval)
 284                 return retval;
 285
 286         driver->driver.bus = &scmi_bus_type;
 287         driver->driver.name = driver->name;
 288         driver->driver.owner = owner;
 289         driver->driver.mod_name = mod_name;
 290
 291         retval = driver_register(&driver->driver);
 292         if (!retval)
 293                 pr_debug("Registered new scmi driver %s\n", driver->name);
 294
 295         return retval;
 296 }
 297 EXPORT_SYMBOL_GPL(scmi_driver_register);
 298
 299 void scmi_driver_unregister(struct scmi_driver *driver)
 300 {
 301         driver_unregister(&driver->driver);
 302         scmi_protocol_device_unrequest(driver->id_table);
 303 }
 304 EXPORT_SYMBOL_GPL(scmi_driver_unregister);
 305
 306 static void scmi_device_release(struct device *dev)
 307 {
 308         kfree(to_scmi_dev(dev));
 309 }
 310
 311 static void __scmi_device_destroy(struct scmi_device *scmi_dev)
 312 {
 313         pr_debug("(%s) Destroying SCMI device '%s' for protocol 0x%x (%s)\n",
 314                  of_node_full_name(scmi_dev->dev.parent->of_node),
 315                  dev_name(&scmi_dev->dev), scmi_dev->protocol_id,
 316                  scmi_dev->name);
 317
 318         if (scmi_dev->protocol_id == SCMI_PROTOCOL_SYSTEM)
 319                 atomic_set(&scmi_syspower_registered, 0);
 320
 321         kfree_const(scmi_dev->name);
 322         ida_free(&scmi_bus_id, scmi_dev->id);
 323         device_unregister(&scmi_dev->dev);
 324 }
 325
 326 static struct scmi_device *
 327 __scmi_device_create(struct device_node *np, struct device *parent,
 328                      int protocol, const char *name)
 329 {
 330         int id, retval;
 331         struct scmi_device *scmi_dev;
 332
 333         /*
 334          * If the same protocol/name device already exist under the same parent
 335          * (i.e. SCMI instance) just return the existent device.
 336          * This avoids any race between the SCMI driver, creating devices for
 337          * each DT defined protocol at probe time, and the concurrent
 338          * registration of SCMI drivers.
 339          */
 340         scmi_dev = scmi_child_dev_find(parent, protocol, name);
 341         if (scmi_dev)
 342                 return scmi_dev;
 343
 344         /*
 345          * Ignore any possible subsequent failures while creating the device
 346          * since we are doomed anyway at that point; not using a mutex which
 347          * spans across this whole function to keep things simple and to avoid
 348          * to serialize all the __scmi_device_create calls across possibly
 349          * different SCMI server instances (parent)
 350          */
 351         if (protocol == SCMI_PROTOCOL_SYSTEM &&
 352             atomic_cmpxchg(&scmi_syspower_registered, 0, 1)) {
 353                 dev_warn(parent,
 354                          "SCMI SystemPower protocol device must be unique !\n");
 355                 return NULL;
 356         }
 357
 358         scmi_dev = kzalloc(sizeof(*scmi_dev), GFP_KERNEL);
 359         if (!scmi_dev)
 360                 return NULL;
 361
 362         scmi_dev->name = kstrdup_const(name ?: "unknown", GFP_KERNEL);
 363         if (!scmi_dev->name) {
 364                 kfree(scmi_dev);
 365                 return NULL;
 366         }
 367
 368         id = ida_alloc_min(&scmi_bus_id, 1, GFP_KERNEL);
 369         if (id < 0) {
 370                 kfree_const(scmi_dev->name);
 371                 kfree(scmi_dev);
 372                 return NULL;
 373         }
 374
 375         scmi_dev->id = id;
 376         scmi_dev->protocol_id = protocol;
 377         scmi_dev->dev.parent = parent;
 378         device_set_node(&scmi_dev->dev, of_fwnode_handle(np));
 379         scmi_dev->dev.bus = &scmi_bus_type;
 380         scmi_dev->dev.release = scmi_device_release;
 381         dev_set_name(&scmi_dev->dev, "scmi_dev.%d", id);
 382
 383         retval = device_register(&scmi_dev->dev);
 384         if (retval)
 385                 goto put_dev;
 386
 387         pr_debug("(%s) Created SCMI device '%s' for protocol 0x%x (%s)\n",
 388                  of_node_full_name(parent->of_node),
 389                  dev_name(&scmi_dev->dev), protocol, name);
 390
 391         return scmi_dev;
 392 put_dev:
 393         kfree_const(scmi_dev->name);
 394         put_device(&scmi_dev->dev);
 395         ida_free(&scmi_bus_id, id);
 396         return NULL;
 397 }
 398
 399 /**
 400  * scmi_device_create  - A method to create one or more SCMI devices
 401  *
 402  * @np: A reference to the device node to use for the new device(s)
 403  * @parent: The parent device to use identifying a specific SCMI instance
 404  * @protocol: The SCMI protocol to be associated with this device
 405  * @name: The requested-name of the device to be created; this is optional
 406  *        and if no @name is provided, all the devices currently known to
 407  *        be requested on the SCMI bus for @protocol will be created.
 408  *
 409  * This method can be invoked to create a single well-defined device (like
 410  * a transport device or a device requested by an SCMI driver loaded after
 411  * the core SCMI stack has been probed), or to create all the devices currently
 412  * known to have been requested by the loaded SCMI drivers for a specific
 413  * protocol (typically during SCMI core protocol enumeration at probe time).
 414  *
 415  * Return: The created device (or one of them if @name was NOT provided and
 416  *         multiple devices were created) or NULL if no device was created;
 417  *         note that NULL indicates an error ONLY in case a specific @name
 418  *         was provided: when @name param was not provided, a number of devices
 419  *         could have been potentially created for a whole protocol, unless no
 420  *         device was found to have been requested for that specific protocol.
 421  */
 422 struct scmi_device *scmi_device_create(struct device_node *np,
 423                                        struct device *parent, int protocol,
 424                                        const char *name)
 425 {
 426         struct list_head *phead;
 427         struct scmi_requested_dev *rdev;
 428         struct scmi_device *scmi_dev = NULL;
 429
 430         if (name)
 431                 return __scmi_device_create(np, parent, protocol, name);
 432
 433         mutex_lock(&scmi_requested_devices_mtx);
 434         phead = idr_find(&scmi_requested_devices, protocol);
 435         /* Nothing to do. */
 436         if (!phead) {
 437                 mutex_unlock(&scmi_requested_devices_mtx);
 438                 return NULL;
 439         }
 440
 441         /* Walk the list of requested devices for protocol and create them */
 442         list_for_each_entry(rdev, phead, node) {
 443                 struct scmi_device *sdev;
 444
 445                 sdev = __scmi_device_create(np, parent,
 446                                             rdev->id_table->protocol_id,
 447                                             rdev->id_table->name);
 448                 /* Report errors and carry on... */
 449                 if (sdev)
 450                         scmi_dev = sdev;
 451                 else
 452                         pr_err("(%s) Failed to create device for protocol 0x%x (%s)\n",
 453                                of_node_full_name(parent->of_node),
 454                                rdev->id_table->protocol_id,
 455                                rdev->id_table->name);
 456         }
 457         mutex_unlock(&scmi_requested_devices_mtx);
 458
 459         return scmi_dev;
 460 }
 461 EXPORT_SYMBOL_GPL(scmi_device_create);
 462
 463 void scmi_device_destroy(struct device *parent, int protocol, const char *name)
 464 {
 465         struct scmi_device *scmi_dev;
 466
 467         scmi_dev = scmi_child_dev_find(parent, protocol, name);
 468         if (scmi_dev)
 469                 __scmi_device_destroy(scmi_dev);
 470 }
 471 EXPORT_SYMBOL_GPL(scmi_device_destroy);
 472
 473 static int __scmi_devices_unregister(struct device *dev, void *data)
 474 {
 475         struct scmi_device *scmi_dev = to_scmi_dev(dev);
 476
 477         __scmi_device_destroy(scmi_dev);
 478         return 0;
 479 }
 480
 481 static void scmi_devices_unregister(void)
 482 {
 483         bus_for_each_dev(&scmi_bus_type, NULL, NULL, __scmi_devices_unregister);
 484 }
 485
 486 static int __init scmi_bus_init(void)
 487 {
 488         int retval;
 489
 490         retval = bus_register(&scmi_bus_type);
 491         if (retval)
 492                 pr_err("SCMI protocol bus register failed (%d)\n", retval);
 493
 494         pr_info("SCMI protocol bus registered\n");
 495
 496         return retval;
 497 }
 498 subsys_initcall(scmi_bus_init);
 499
 500 static void __exit scmi_bus_exit(void)
 501 {
 502         /*
 503          * Destroy all remaining devices: just in case the drivers were
 504          * manually unbound and at first and then the modules unloaded.
 505          */
 506         scmi_devices_unregister();
 507         bus_unregister(&scmi_bus_type);
 508         ida_destroy(&scmi_bus_id);
 509 }
 510 module_exit(scmi_bus_exit);
 511
 512 MODULE_ALIAS("scmi-core");
 513 MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
 514 MODULE_DESCRIPTION("ARM SCMI protocol bus");
 515 MODULE_LICENSE("GPL");