drivers/bus/mips_cdmm.c

   1 /*
   2  * Bus driver for MIPS Common Device Memory Map (CDMM).
   3  *
   4  * Copyright (C) 2014-2015 Imagination Technologies Ltd.
   5  *
   6  * This file is subject to the terms and conditions of the GNU General Public
   7  * License.  See the file "COPYING" in the main directory of this archive
   8  * for more details.
   9  */
  10
  11 #include <linux/atomic.h>
  12 #include <linux/err.h>
  13 #include <linux/cpu.h>
  14 #include <linux/cpumask.h>
  15 #include <linux/io.h>
  16 #include <linux/platform_device.h>
  17 #include <linux/slab.h>
  18 #include <linux/smp.h>
  19 #include <asm/cdmm.h>
  20 #include <asm/hazards.h>
  21 #include <asm/mipsregs.h>
  22
  23 /* Access control and status register fields */
  24 #define CDMM_ACSR_DEVTYPE_SHIFT 24
  25 #define CDMM_ACSR_DEVTYPE       (255ul << CDMM_ACSR_DEVTYPE_SHIFT)
  26 #define CDMM_ACSR_DEVSIZE_SHIFT 16
  27 #define CDMM_ACSR_DEVSIZE       (31ul << CDMM_ACSR_DEVSIZE_SHIFT)
  28 #define CDMM_ACSR_DEVREV_SHIFT  12
  29 #define CDMM_ACSR_DEVREV        (15ul << CDMM_ACSR_DEVREV_SHIFT)
  30 #define CDMM_ACSR_UW            (1ul << 3)
  31 #define CDMM_ACSR_UR            (1ul << 2)
  32 #define CDMM_ACSR_SW            (1ul << 1)
  33 #define CDMM_ACSR_SR            (1ul << 0)
  34
  35 /* Each block of device registers is 64 bytes */
  36 #define CDMM_DRB_SIZE           64
  37
  38 #define to_mips_cdmm_driver(d)  container_of(d, struct mips_cdmm_driver, drv)
  39
  40 /* Default physical base address */
  41 static phys_addr_t mips_cdmm_default_base;
  42
  43 /* Bus operations */
  44
  45 static const struct mips_cdmm_device_id *
  46 mips_cdmm_lookup(const struct mips_cdmm_device_id *table,
  47                  struct mips_cdmm_device *dev)
  48 {
  49         int ret = 0;
  50
  51         for (; table->type; ++table) {
  52                 ret = (dev->type == table->type);
  53                 if (ret)
  54                         break;
  55         }
  56
  57         return ret ? table : NULL;
  58 }
  59
  60 static int mips_cdmm_match(struct device *dev, struct device_driver *drv)
  61 {
  62         struct mips_cdmm_device *cdev = to_mips_cdmm_device(dev);
  63         struct mips_cdmm_driver *cdrv = to_mips_cdmm_driver(drv);
  64
  65         return mips_cdmm_lookup(cdrv->id_table, cdev) != NULL;
  66 }
  67
  68 static int mips_cdmm_uevent(struct device *dev, struct kobj_uevent_env *env)
  69 {
  70         struct mips_cdmm_device *cdev = to_mips_cdmm_device(dev);
  71         int retval = 0;
  72
  73         retval = add_uevent_var(env, "CDMM_CPU=%u", cdev->cpu);
  74         if (retval)
  75                 return retval;
  76
  77         retval = add_uevent_var(env, "CDMM_TYPE=0x%02x", cdev->type);
  78         if (retval)
  79                 return retval;
  80
  81         retval = add_uevent_var(env, "CDMM_REV=%u", cdev->rev);
  82         if (retval)
  83                 return retval;
  84
  85         retval = add_uevent_var(env, "MODALIAS=mipscdmm:t%02X", cdev->type);
  86         return retval;
  87 }
  88
  89 /* Device attributes */
  90
  91 #define CDMM_ATTR(name, fmt, arg...)                                    \
  92 static ssize_t name##_show(struct device *_dev,                         \
  93                            struct device_attribute *attr, char *buf)    \
  94 {                                                                       \
  95         struct mips_cdmm_device *dev = to_mips_cdmm_device(_dev);       \
  96         return sprintf(buf, fmt, arg);                                  \
  97 }                                                                       \
  98 static DEVICE_ATTR_RO(name);
  99
 100 CDMM_ATTR(cpu, "%u\n", dev->cpu);
 101 CDMM_ATTR(type, "0x%02x\n", dev->type);
 102 CDMM_ATTR(revision, "%u\n", dev->rev);
 103 CDMM_ATTR(modalias, "mipscdmm:t%02X\n", dev->type);
 104 CDMM_ATTR(resource, "\t%016llx\t%016llx\t%016lx\n",
 105           (unsigned long long)dev->res.start,
 106           (unsigned long long)dev->res.end,
 107           dev->res.flags);
 108
 109 static struct attribute *mips_cdmm_dev_attrs[] = {
 110         &dev_attr_cpu.attr,
 111         &dev_attr_type.attr,
 112         &dev_attr_revision.attr,
 113         &dev_attr_modalias.attr,
 114         &dev_attr_resource.attr,
 115         NULL,
 116 };
 117 ATTRIBUTE_GROUPS(mips_cdmm_dev);
 118
 119 struct bus_type mips_cdmm_bustype = {
 120         .name           = "cdmm",
 121         .dev_groups     = mips_cdmm_dev_groups,
 122         .match          = mips_cdmm_match,
 123         .uevent         = mips_cdmm_uevent,
 124 };
 125 EXPORT_SYMBOL_GPL(mips_cdmm_bustype);
 126
 127 /*
 128  * Standard driver callback helpers.
 129  *
 130  * All the CDMM driver callbacks need to be executed on the appropriate CPU from
 131  * workqueues. For the standard driver callbacks we need a work function
 132  * (mips_cdmm_{void,int}_work()) to do the actual call from the right CPU, and a
 133  * wrapper function (generated with BUILD_PERCPU_HELPER) to arrange for the work
 134  * function to be called on that CPU.
 135  */
 136
 137 /**
 138  * struct mips_cdmm_work_dev - Data for per-device call work.
 139  * @fn:         CDMM driver callback function to call for the device.
 140  * @dev:        CDMM device to pass to @fn.
 141  */
 142 struct mips_cdmm_work_dev {
 143         void                    *fn;
 144         struct mips_cdmm_device *dev;
 145 };
 146
 147 /**
 148  * mips_cdmm_void_work() - Call a void returning CDMM driver callback.
 149  * @data:       struct mips_cdmm_work_dev pointer.
 150  *
 151  * A work_on_cpu() callback function to call an arbitrary CDMM driver callback
 152  * function which doesn't return a value.
 153  */
 154 static long mips_cdmm_void_work(void *data)
 155 {
 156         struct mips_cdmm_work_dev *work = data;
 157         void (*fn)(struct mips_cdmm_device *) = work->fn;
 158
 159         fn(work->dev);
 160         return 0;
 161 }
 162
 163 /**
 164  * mips_cdmm_int_work() - Call an int returning CDMM driver callback.
 165  * @data:       struct mips_cdmm_work_dev pointer.
 166  *
 167  * A work_on_cpu() callback function to call an arbitrary CDMM driver callback
 168  * function which returns an int.
 169  */
 170 static long mips_cdmm_int_work(void *data)
 171 {
 172         struct mips_cdmm_work_dev *work = data;
 173         int (*fn)(struct mips_cdmm_device *) = work->fn;
 174
 175         return fn(work->dev);
 176 }
 177
 178 #define _BUILD_RET_void
 179 #define _BUILD_RET_int  return
 180
 181 /**
 182  * BUILD_PERCPU_HELPER() - Helper to call a CDMM driver callback on right CPU.
 183  * @_ret:       Return type (void or int).
 184  * @_name:      Name of CDMM driver callback function.
 185  *
 186  * Generates a specific device callback function to call a CDMM driver callback
 187  * function on the appropriate CPU for the device, and if applicable return the
 188  * result.
 189  */
 190 #define BUILD_PERCPU_HELPER(_ret, _name)                                \
 191 static _ret mips_cdmm_##_name(struct device *dev)                       \
 192 {                                                                       \
 193         struct mips_cdmm_device *cdev = to_mips_cdmm_device(dev);       \
 194         struct mips_cdmm_driver *cdrv = to_mips_cdmm_driver(dev->driver); \
 195         struct mips_cdmm_work_dev work = {                              \
 196                 .fn     = cdrv->_name,                                  \
 197                 .dev    = cdev,                                         \
 198         };                                                              \
 199                                                                         \
 200         _BUILD_RET_##_ret work_on_cpu(cdev->cpu,                        \
 201                                       mips_cdmm_##_ret##_work, &work);  \
 202 }
 203
 204 /* Driver callback functions */
 205 BUILD_PERCPU_HELPER(int, probe)     /* int mips_cdmm_probe(struct device) */
 206 BUILD_PERCPU_HELPER(int, remove)    /* int mips_cdmm_remove(struct device) */
 207 BUILD_PERCPU_HELPER(void, shutdown) /* void mips_cdmm_shutdown(struct device) */
 208
 209
 210 /* Driver registration */
 211
 212 /**
 213  * mips_cdmm_driver_register() - Register a CDMM driver.
 214  * @drv:        CDMM driver information.
 215  *
 216  * Register a CDMM driver with the CDMM subsystem. The driver will be informed
 217  * of matching devices which are discovered.
 218  *
 219  * Returns:     0 on success.
 220  */
 221 int mips_cdmm_driver_register(struct mips_cdmm_driver *drv)
 222 {
 223         drv->drv.bus = &mips_cdmm_bustype;
 224
 225         if (drv->probe)
 226                 drv->drv.probe = mips_cdmm_probe;
 227         if (drv->remove)
 228                 drv->drv.remove = mips_cdmm_remove;
 229         if (drv->shutdown)
 230                 drv->drv.shutdown = mips_cdmm_shutdown;
 231
 232         return driver_register(&drv->drv);
 233 }
 234 EXPORT_SYMBOL_GPL(mips_cdmm_driver_register);
 235
 236 /**
 237  * mips_cdmm_driver_unregister() - Unregister a CDMM driver.
 238  * @drv:        CDMM driver information.
 239  *
 240  * Unregister a CDMM driver from the CDMM subsystem.
 241  */
 242 void mips_cdmm_driver_unregister(struct mips_cdmm_driver *drv)
 243 {
 244         driver_unregister(&drv->drv);
 245 }
 246 EXPORT_SYMBOL_GPL(mips_cdmm_driver_unregister);
 247
 248
 249 /* CDMM initialisation and bus discovery */
 250
 251 /**
 252  * struct mips_cdmm_bus - Info about CDMM bus.
 253  * @phys:               Physical address at which it is mapped.
 254  * @regs:               Virtual address where registers can be accessed.
 255  * @drbs:               Total number of DRBs.
 256  * @drbs_reserved:      Number of DRBs reserved.
 257  * @discovered:         Whether the devices on the bus have been discovered yet.
 258  * @offline:            Whether the CDMM bus is going offline (or very early
 259  *                      coming back online), in which case it should be
 260  *                      reconfigured each time.
 261  */
 262 struct mips_cdmm_bus {
 263         phys_addr_t      phys;
 264         void __iomem    *regs;
 265         unsigned int     drbs;
 266         unsigned int     drbs_reserved;
 267         bool             discovered;
 268         bool             offline;
 269 };
 270
 271 static struct mips_cdmm_bus mips_cdmm_boot_bus;
 272 static DEFINE_PER_CPU(struct mips_cdmm_bus *, mips_cdmm_buses);
 273 static atomic_t mips_cdmm_next_id = ATOMIC_INIT(-1);
 274
 275 /**
 276  * mips_cdmm_get_bus() - Get the per-CPU CDMM bus information.
 277  *
 278  * Get information about the per-CPU CDMM bus, if the bus is present.
 279  *
 280  * The caller must prevent migration to another CPU, either by disabling
 281  * pre-emption or by running from a pinned kernel thread.
 282  *
 283  * Returns:     Pointer to CDMM bus information for the current CPU.
 284  *              May return ERR_PTR(-errno) in case of error, so check with
 285  *              IS_ERR().
 286  */
 287 static struct mips_cdmm_bus *mips_cdmm_get_bus(void)
 288 {
 289         struct mips_cdmm_bus *bus, **bus_p;
 290         unsigned long flags;
 291         unsigned int cpu;
 292
 293         if (!cpu_has_cdmm)
 294                 return ERR_PTR(-ENODEV);
 295
 296         cpu = smp_processor_id();
 297         /* Avoid early use of per-cpu primitives before initialised */
 298         if (cpu == 0)
 299                 return &mips_cdmm_boot_bus;
 300
 301         /* Get bus pointer */
 302         bus_p = per_cpu_ptr(&mips_cdmm_buses, cpu);
 303         local_irq_save(flags);
 304         bus = *bus_p;
 305         /* Attempt allocation if NULL */
 306         if (unlikely(!bus)) {
 307                 bus = kzalloc(sizeof(*bus), GFP_ATOMIC);
 308                 if (unlikely(!bus))
 309                         bus = ERR_PTR(-ENOMEM);
 310                 else
 311                         *bus_p = bus;
 312         }
 313         local_irq_restore(flags);
 314         return bus;
 315 }
 316
 317 /**
 318  * mips_cdmm_cur_base() - Find current physical base address of CDMM region.
 319  *
 320  * Returns:     Physical base address of CDMM region according to cdmmbase CP0
 321  *              register, or 0 if the CDMM region is disabled.
 322  */
 323 static phys_addr_t mips_cdmm_cur_base(void)
 324 {
 325         unsigned long cdmmbase = read_c0_cdmmbase();
 326
 327         if (!(cdmmbase & MIPS_CDMMBASE_EN))
 328                 return 0;
 329
 330         return (cdmmbase >> MIPS_CDMMBASE_ADDR_SHIFT)
 331                 << MIPS_CDMMBASE_ADDR_START;
 332 }
 333
 334 /**
 335  * mips_cdmm_setup() - Ensure the CDMM bus is initialised and usable.
 336  * @bus:        Pointer to bus information for current CPU.
 337  *              IS_ERR(bus) is checked, so no need for caller to check.
 338  *
 339  * The caller must prevent migration to another CPU, either by disabling
 340  * pre-emption or by running from a pinned kernel thread.
 341  *
 342  * Returns      0 on success, -errno on failure.
 343  */
 344 static int mips_cdmm_setup(struct mips_cdmm_bus *bus)
 345 {
 346         unsigned long cdmmbase, flags;
 347         int ret = 0;
 348
 349         if (IS_ERR(bus))
 350                 return PTR_ERR(bus);
 351
 352         local_irq_save(flags);
 353         /* Don't set up bus a second time unless marked offline */
 354         if (bus->offline) {
 355                 /* If CDMM region is still set up, nothing to do */
 356                 if (bus->phys == mips_cdmm_cur_base())
 357                         goto out;
 358                 /*
 359                  * The CDMM region isn't set up as expected, so it needs
 360                  * reconfiguring, but then we can stop checking it.
 361                  */
 362                 bus->offline = false;
 363         } else if (bus->phys > 1) {
 364                 goto out;
 365         }
 366
 367         /* If the CDMM region is already configured, inherit that setup */
 368         if (!bus->phys)
 369                 bus->phys = mips_cdmm_cur_base();
 370         /* Otherwise, ask platform code for suggestions */
 371         if (!bus->phys && mips_cdmm_phys_base)
 372                 bus->phys = mips_cdmm_phys_base();
 373         /* Otherwise, copy what other CPUs have done */
 374         if (!bus->phys)
 375                 bus->phys = mips_cdmm_default_base;
 376         /* Otherwise, complain once */
 377         if (!bus->phys) {
 378                 bus->phys = 1;
 379                 /*
 380                  * If you hit this, either your bootloader needs to set up the
 381                  * CDMM on the boot CPU, or else you need to implement
 382                  * mips_cdmm_phys_base() for your platform (see asm/cdmm.h).
 383                  */
 384                 pr_err("cdmm%u: Failed to choose a physical base\n",
 385                        smp_processor_id());
 386         }
 387         /* Already complained? */
 388         if (bus->phys == 1) {
 389                 ret = -ENOMEM;
 390                 goto out;
 391         }
 392         /* Record our success for other CPUs to copy */
 393         mips_cdmm_default_base = bus->phys;
 394
 395         pr_debug("cdmm%u: Enabling CDMM region at %pa\n",
 396                  smp_processor_id(), &bus->phys);
 397
 398         /* Enable CDMM */
 399         cdmmbase = read_c0_cdmmbase();
 400         cdmmbase &= (1ul << MIPS_CDMMBASE_ADDR_SHIFT) - 1;
 401         cdmmbase |= (bus->phys >> MIPS_CDMMBASE_ADDR_START)
 402                         << MIPS_CDMMBASE_ADDR_SHIFT;
 403         cdmmbase |= MIPS_CDMMBASE_EN;
 404         write_c0_cdmmbase(cdmmbase);
 405         tlbw_use_hazard();
 406
 407         bus->regs = (void __iomem *)CKSEG1ADDR(bus->phys);
 408         bus->drbs = 1 + ((cdmmbase & MIPS_CDMMBASE_SIZE) >>
 409                          MIPS_CDMMBASE_SIZE_SHIFT);
 410         bus->drbs_reserved = !!(cdmmbase & MIPS_CDMMBASE_CI);
 411
 412 out:
 413         local_irq_restore(flags);
 414         return ret;
 415 }
 416
 417 /**
 418  * mips_cdmm_early_probe() - Minimally probe for a specific device on CDMM.
 419  * @dev_type:   CDMM type code to look for.
 420  *
 421  * Minimally configure the in-CPU Common Device Memory Map (CDMM) and look for a
 422  * specific device. This can be used to find a device very early in boot for
 423  * example to configure an early FDC console device.
 424  *
 425  * The caller must prevent migration to another CPU, either by disabling
 426  * pre-emption or by running from a pinned kernel thread.
 427  *
 428  * Returns:     MMIO pointer to device memory. The caller can read the ACSR
 429  *              register to find more information about the device (such as the
 430  *              version number or the number of blocks).
 431  *              May return IOMEM_ERR_PTR(-errno) in case of error, so check with
 432  *              IS_ERR().
 433  */
 434 void __iomem *mips_cdmm_early_probe(unsigned int dev_type)
 435 {
 436         struct mips_cdmm_bus *bus;
 437         void __iomem *cdmm;
 438         u32 acsr;
 439         unsigned int drb, type, size;
 440         int err;
 441
 442         if (WARN_ON(!dev_type))
 443                 return IOMEM_ERR_PTR(-ENODEV);
 444
 445         bus = mips_cdmm_get_bus();
 446         err = mips_cdmm_setup(bus);
 447         if (err)
 448                 return IOMEM_ERR_PTR(err);
 449
 450         /* Skip the first block if it's reserved for more registers */
 451         drb = bus->drbs_reserved;
 452         cdmm = bus->regs;
 453
 454         /* Look for a specific device type */
 455         for (; drb < bus->drbs; drb += size + 1) {
 456                 acsr = readl(cdmm + drb * CDMM_DRB_SIZE);
 457                 type = (acsr & CDMM_ACSR_DEVTYPE) >> CDMM_ACSR_DEVTYPE_SHIFT;
 458                 if (type == dev_type)
 459                         return cdmm + drb * CDMM_DRB_SIZE;
 460                 size = (acsr & CDMM_ACSR_DEVSIZE) >> CDMM_ACSR_DEVSIZE_SHIFT;
 461         }
 462
 463         return IOMEM_ERR_PTR(-ENODEV);
 464 }
 465 EXPORT_SYMBOL_GPL(mips_cdmm_early_probe);
 466
 467 /**
 468  * mips_cdmm_release() - Release a removed CDMM device.
 469  * @dev:        Device object
 470  *
 471  * Clean up the struct mips_cdmm_device for an unused CDMM device. This is
 472  * called automatically by the driver core when a device is removed.
 473  */
 474 static void mips_cdmm_release(struct device *dev)
 475 {
 476         struct mips_cdmm_device *cdev = to_mips_cdmm_device(dev);
 477
 478         kfree(cdev);
 479 }
 480
 481 /**
 482  * mips_cdmm_bus_discover() - Discover the devices on the CDMM bus.
 483  * @bus:        CDMM bus information, must already be set up.
 484  */
 485 static void mips_cdmm_bus_discover(struct mips_cdmm_bus *bus)
 486 {
 487         void __iomem *cdmm;
 488         u32 acsr;
 489         unsigned int drb, type, size, rev;
 490         struct mips_cdmm_device *dev;
 491         unsigned int cpu = smp_processor_id();
 492         int ret = 0;
 493         int id = 0;
 494
 495         /* Skip the first block if it's reserved for more registers */
 496         drb = bus->drbs_reserved;
 497         cdmm = bus->regs;
 498
 499         /* Discover devices */
 500         bus->discovered = true;
 501         pr_info("cdmm%u discovery (%u blocks)\n", cpu, bus->drbs);
 502         for (; drb < bus->drbs; drb += size + 1) {
 503                 acsr = readl(cdmm + drb * CDMM_DRB_SIZE);
 504                 type = (acsr & CDMM_ACSR_DEVTYPE) >> CDMM_ACSR_DEVTYPE_SHIFT;
 505                 size = (acsr & CDMM_ACSR_DEVSIZE) >> CDMM_ACSR_DEVSIZE_SHIFT;
 506                 rev  = (acsr & CDMM_ACSR_DEVREV)  >> CDMM_ACSR_DEVREV_SHIFT;
 507
 508                 if (!type)
 509                         continue;
 510
 511                 pr_info("cdmm%u-%u: @%u (%#x..%#x), type 0x%02x, rev %u\n",
 512                         cpu, id, drb, drb * CDMM_DRB_SIZE,
 513                         (drb + size + 1) * CDMM_DRB_SIZE - 1,
 514                         type, rev);
 515
 516                 dev = kzalloc(sizeof(*dev), GFP_KERNEL);
 517                 if (!dev)
 518                         break;
 519
 520                 dev->cpu = cpu;
 521                 dev->res.start = bus->phys + drb * CDMM_DRB_SIZE;
 522                 dev->res.end = bus->phys +
 523                                 (drb + size + 1) * CDMM_DRB_SIZE - 1;
 524                 dev->res.flags = IORESOURCE_MEM;
 525                 dev->type = type;
 526                 dev->rev = rev;
 527                 dev->dev.parent = get_cpu_device(cpu);
 528                 dev->dev.bus = &mips_cdmm_bustype;
 529                 dev->dev.id = atomic_inc_return(&mips_cdmm_next_id);
 530                 dev->dev.release = mips_cdmm_release;
 531
 532                 dev_set_name(&dev->dev, "cdmm%u-%u", cpu, id);
 533                 ++id;
 534                 ret = device_register(&dev->dev);
 535                 if (ret) {
 536                         put_device(&dev->dev);
 537                         kfree(dev);
 538                 }
 539         }
 540 }
 541
 542
 543 /*
 544  * CPU hotplug and initialisation
 545  *
 546  * All the CDMM driver callbacks need to be executed on the appropriate CPU from
 547  * workqueues. For the CPU callbacks, they need to be called for all devices on
 548  * that CPU, so the work function calls bus_for_each_dev, using a helper
 549  * (generated with BUILD_PERDEV_HELPER) to call the driver callback if the
 550  * device's CPU matches.
 551  */
 552
 553 /**
 554  * BUILD_PERDEV_HELPER() - Helper to call a CDMM driver callback if CPU matches.
 555  * @_name:      Name of CDMM driver callback function.
 556  *
 557  * Generates a bus_for_each_dev callback function to call a specific CDMM driver
 558  * callback function for the device if the device's CPU matches that pointed to
 559  * by the data argument.
 560  *
 561  * This is used for informing drivers for all devices on a given CPU of some
 562  * event (such as the CPU going online/offline).
 563  *
 564  * It is expected to already be called from the appropriate CPU.
 565  */
 566 #define BUILD_PERDEV_HELPER(_name)                                      \
 567 static int mips_cdmm_##_name##_helper(struct device *dev, void *data)   \
 568 {                                                                       \
 569         struct mips_cdmm_device *cdev = to_mips_cdmm_device(dev);       \
 570         struct mips_cdmm_driver *cdrv;                                  \
 571         unsigned int cpu = *(unsigned int *)data;                       \
 572                                                                         \
 573         if (cdev->cpu != cpu || !dev->driver)                           \
 574                 return 0;                                               \
 575                                                                         \
 576         cdrv = to_mips_cdmm_driver(dev->driver);                        \
 577         if (!cdrv->_name)                                               \
 578                 return 0;                                               \
 579         return cdrv->_name(cdev);                                       \
 580 }
 581
 582 /* bus_for_each_dev callback helper functions */
 583 BUILD_PERDEV_HELPER(cpu_down)       /* int mips_cdmm_cpu_down_helper(...) */
 584 BUILD_PERDEV_HELPER(cpu_up)         /* int mips_cdmm_cpu_up_helper(...) */
 585
 586 /**
 587  * mips_cdmm_bus_down() - Tear down the CDMM bus.
 588  * @data:       Pointer to unsigned int CPU number.
 589  *
 590  * This work_on_cpu callback function is executed on a given CPU to call the
 591  * CDMM driver cpu_down callback for all devices on that CPU.
 592  */
 593 static long mips_cdmm_bus_down(void *data)
 594 {
 595         struct mips_cdmm_bus *bus;
 596         long ret;
 597
 598         /* Inform all the devices on the bus */
 599         ret = bus_for_each_dev(&mips_cdmm_bustype, NULL, data,
 600                                mips_cdmm_cpu_down_helper);
 601
 602         /*
 603          * While bus is offline, each use of it should reconfigure it just in
 604          * case it is first use when coming back online again.
 605          */
 606         bus = mips_cdmm_get_bus();
 607         if (!IS_ERR(bus))
 608                 bus->offline = true;
 609
 610         return ret;
 611 }
 612
 613 /**
 614  * mips_cdmm_bus_up() - Bring up the CDMM bus.
 615  * @data:       Pointer to unsigned int CPU number.
 616  *
 617  * This work_on_cpu callback function is executed on a given CPU to discover
 618  * CDMM devices on that CPU, or to call the CDMM driver cpu_up callback for all
 619  * devices already discovered on that CPU.
 620  *
 621  * It is used during initialisation and when CPUs are brought online.
 622  */
 623 static long mips_cdmm_bus_up(void *data)
 624 {
 625         struct mips_cdmm_bus *bus;
 626         long ret;
 627
 628         bus = mips_cdmm_get_bus();
 629         ret = mips_cdmm_setup(bus);
 630         if (ret)
 631                 return ret;
 632
 633         /* Bus now set up, so we can drop the offline flag if still set */
 634         bus->offline = false;
 635
 636         if (!bus->discovered)
 637                 mips_cdmm_bus_discover(bus);
 638         else
 639                 /* Inform all the devices on the bus */
 640                 ret = bus_for_each_dev(&mips_cdmm_bustype, NULL, data,
 641                                        mips_cdmm_cpu_up_helper);
 642
 643         return ret;
 644 }
 645
 646 /**
 647  * mips_cdmm_cpu_notify() - Take action when a CPU is going online or offline.
 648  * @nb:         CPU notifier block .
 649  * @action:     Event that has taken place (CPU_*).
 650  * @data:       CPU number.
 651  *
 652  * This notifier is used to keep the CDMM buses updated as CPUs are offlined and
 653  * onlined. When CPUs go offline or come back online, so does their CDMM bus, so
 654  * devices must be informed. Also when CPUs come online for the first time the
 655  * devices on the CDMM bus need discovering.
 656  *
 657  * Returns:     NOTIFY_OK if event was used.
 658  *              NOTIFY_DONE if we didn't care.
 659  */
 660 static int mips_cdmm_cpu_notify(struct notifier_block *nb,
 661                                 unsigned long action, void *data)
 662 {
 663         unsigned int cpu = (unsigned int)data;
 664
 665         switch (action & ~CPU_TASKS_FROZEN) {
 666         case CPU_ONLINE:
 667         case CPU_DOWN_FAILED:
 668                 work_on_cpu(cpu, mips_cdmm_bus_up, &cpu);
 669                 break;
 670         case CPU_DOWN_PREPARE:
 671                 work_on_cpu(cpu, mips_cdmm_bus_down, &cpu);
 672                 break;
 673         default:
 674                 return NOTIFY_DONE;
 675         }
 676
 677         return NOTIFY_OK;
 678 }
 679
 680 static struct notifier_block mips_cdmm_cpu_nb = {
 681         .notifier_call = mips_cdmm_cpu_notify,
 682 };
 683
 684 /**
 685  * mips_cdmm_init() - Initialise CDMM bus.
 686  *
 687  * Initialise CDMM bus, discover CDMM devices for online CPUs, and arrange for
 688  * hotplug notifications so the CDMM drivers can be kept up to date.
 689  */
 690 static int __init mips_cdmm_init(void)
 691 {
 692         unsigned int cpu;
 693         int ret;
 694
 695         /* Register the bus */
 696         ret = bus_register(&mips_cdmm_bustype);
 697         if (ret)
 698                 return ret;
 699
 700         /* We want to be notified about new CPUs */
 701         ret = register_cpu_notifier(&mips_cdmm_cpu_nb);
 702         if (ret) {
 703                 pr_warn("cdmm: Failed to register CPU notifier\n");
 704                 goto out;
 705         }
 706
 707         /* Discover devices on CDMM of online CPUs */
 708         for_each_online_cpu(cpu)
 709                 work_on_cpu(cpu, mips_cdmm_bus_up, &cpu);
 710
 711         return 0;
 712 out:
 713         bus_unregister(&mips_cdmm_bustype);
 714         return ret;
 715 }
 716 subsys_initcall(mips_cdmm_init);