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_phys_base() - Choose a physical base address for CDMM region.
336 *
337 * Picking a suitable physical address at which to map the CDMM region is
338 * platform specific, so this weak function can be overridden by platform
339 * code to pick a suitable value if none is configured by the bootloader.
340 */
341 phys_addr_t __weak mips_cdmm_phys_base(void)
342 {
343 return 0;
344 }
345
346 /**
347 * mips_cdmm_setup() - Ensure the CDMM bus is initialised and usable.
348 * @bus: Pointer to bus information for current CPU.
349 * IS_ERR(bus) is checked, so no need for caller to check.
350 *
351 * The caller must prevent migration to another CPU, either by disabling
352 * pre-emption or by running from a pinned kernel thread.
353 *
354 * Returns 0 on success, -errno on failure.
355 */
356 static int mips_cdmm_setup(struct mips_cdmm_bus *bus)
357 {
358 unsigned long cdmmbase, flags;
359 int ret = 0;
360
361 if (IS_ERR(bus))
362 return PTR_ERR(bus);
363
364 local_irq_save(flags);
365 /* Don't set up bus a second time unless marked offline */
366 if (bus->offline) {
367 /* If CDMM region is still set up, nothing to do */
368 if (bus->phys == mips_cdmm_cur_base())
369 goto out;
370 /*
371 * The CDMM region isn't set up as expected, so it needs
372 * reconfiguring, but then we can stop checking it.
373 */
374 bus->offline = false;
375 } else if (bus->phys > 1) {
376 goto out;
377 }
378
379 /* If the CDMM region is already configured, inherit that setup */
380 if (!bus->phys)
381 bus->phys = mips_cdmm_cur_base();
382 /* Otherwise, ask platform code for suggestions */
383 if (!bus->phys)
384 bus->phys = mips_cdmm_phys_base();
385 /* Otherwise, copy what other CPUs have done */
386 if (!bus->phys)
387 bus->phys = mips_cdmm_default_base;
388 /* Otherwise, complain once */
389 if (!bus->phys) {
390 bus->phys = 1;
391 /*
392 * If you hit this, either your bootloader needs to set up the
393 * CDMM on the boot CPU, or else you need to implement
394 * mips_cdmm_phys_base() for your platform (see asm/cdmm.h).
395 */
396 pr_err("cdmm%u: Failed to choose a physical base\n",
397 smp_processor_id());
398 }
399 /* Already complained? */
400 if (bus->phys == 1) {
401 ret = -ENOMEM;
402 goto out;
403 }
404 /* Record our success for other CPUs to copy */
405 mips_cdmm_default_base = bus->phys;
406
407 pr_debug("cdmm%u: Enabling CDMM region at %pa\n",
408 smp_processor_id(), &bus->phys);
409
410 /* Enable CDMM */
411 cdmmbase = read_c0_cdmmbase();
412 cdmmbase &= (1ul << MIPS_CDMMBASE_ADDR_SHIFT) - 1;
413 cdmmbase |= (bus->phys >> MIPS_CDMMBASE_ADDR_START)
414 << MIPS_CDMMBASE_ADDR_SHIFT;
415 cdmmbase |= MIPS_CDMMBASE_EN;
416 write_c0_cdmmbase(cdmmbase);
417 tlbw_use_hazard();
418
419 bus->regs = (void __iomem *)CKSEG1ADDR(bus->phys);
420 bus->drbs = 1 + ((cdmmbase & MIPS_CDMMBASE_SIZE) >>
421 MIPS_CDMMBASE_SIZE_SHIFT);
422 bus->drbs_reserved = !!(cdmmbase & MIPS_CDMMBASE_CI);
423
424 out:
425 local_irq_restore(flags);
426 return ret;
427 }
428
429 /**
430 * mips_cdmm_early_probe() - Minimally probe for a specific device on CDMM.
431 * @dev_type: CDMM type code to look for.
432 *
433 * Minimally configure the in-CPU Common Device Memory Map (CDMM) and look for a
434 * specific device. This can be used to find a device very early in boot for
435 * example to configure an early FDC console device.
436 *
437 * The caller must prevent migration to another CPU, either by disabling
438 * pre-emption or by running from a pinned kernel thread.
439 *
440 * Returns: MMIO pointer to device memory. The caller can read the ACSR
441 * register to find more information about the device (such as the
442 * version number or the number of blocks).
443 * May return IOMEM_ERR_PTR(-errno) in case of error, so check with
444 * IS_ERR().
445 */
446 void __iomem *mips_cdmm_early_probe(unsigned int dev_type)
447 {
448 struct mips_cdmm_bus *bus;
449 void __iomem *cdmm;
450 u32 acsr;
451 unsigned int drb, type, size;
452 int err;
453
454 if (WARN_ON(!dev_type))
455 return IOMEM_ERR_PTR(-ENODEV);
456
457 bus = mips_cdmm_get_bus();
458 err = mips_cdmm_setup(bus);
459 if (err)
460 return IOMEM_ERR_PTR(err);
461
462 /* Skip the first block if it's reserved for more registers */
463 drb = bus->drbs_reserved;
464 cdmm = bus->regs;
465
466 /* Look for a specific device type */
467 for (; drb < bus->drbs; drb += size + 1) {
468 acsr = __raw_readl(cdmm + drb * CDMM_DRB_SIZE);
469 type = (acsr & CDMM_ACSR_DEVTYPE) >> CDMM_ACSR_DEVTYPE_SHIFT;
470 if (type == dev_type)
471 return cdmm + drb * CDMM_DRB_SIZE;
472 size = (acsr & CDMM_ACSR_DEVSIZE) >> CDMM_ACSR_DEVSIZE_SHIFT;
473 }
474
475 return IOMEM_ERR_PTR(-ENODEV);
476 }
477 EXPORT_SYMBOL_GPL(mips_cdmm_early_probe);
478
479 /**
480 * mips_cdmm_release() - Release a removed CDMM device.
481 * @dev: Device object
482 *
483 * Clean up the struct mips_cdmm_device for an unused CDMM device. This is
484 * called automatically by the driver core when a device is removed.
485 */
486 static void mips_cdmm_release(struct device *dev)
487 {
488 struct mips_cdmm_device *cdev = to_mips_cdmm_device(dev);
489
490 kfree(cdev);
491 }
492
493 /**
494 * mips_cdmm_bus_discover() - Discover the devices on the CDMM bus.
495 * @bus: CDMM bus information, must already be set up.
496 */
497 static void mips_cdmm_bus_discover(struct mips_cdmm_bus *bus)
498 {
499 void __iomem *cdmm;
500 u32 acsr;
501 unsigned int drb, type, size, rev;
502 struct mips_cdmm_device *dev;
503 unsigned int cpu = smp_processor_id();
504 int ret = 0;
505 int id = 0;
506
507 /* Skip the first block if it's reserved for more registers */
508 drb = bus->drbs_reserved;
509 cdmm = bus->regs;
510
511 /* Discover devices */
512 bus->discovered = true;
513 pr_info("cdmm%u discovery (%u blocks)\n", cpu, bus->drbs);
514 for (; drb < bus->drbs; drb += size + 1) {
515 acsr = __raw_readl(cdmm + drb * CDMM_DRB_SIZE);
516 type = (acsr & CDMM_ACSR_DEVTYPE) >> CDMM_ACSR_DEVTYPE_SHIFT;
517 size = (acsr & CDMM_ACSR_DEVSIZE) >> CDMM_ACSR_DEVSIZE_SHIFT;
518 rev = (acsr & CDMM_ACSR_DEVREV) >> CDMM_ACSR_DEVREV_SHIFT;
519
520 if (!type)
521 continue;
522
523 pr_info("cdmm%u-%u: @%u (%#x..%#x), type 0x%02x, rev %u\n",
524 cpu, id, drb, drb * CDMM_DRB_SIZE,
525 (drb + size + 1) * CDMM_DRB_SIZE - 1,
526 type, rev);
527
528 dev = kzalloc(sizeof(*dev), GFP_KERNEL);
529 if (!dev)
530 break;
531
532 dev->cpu = cpu;
533 dev->res.start = bus->phys + drb * CDMM_DRB_SIZE;
534 dev->res.end = bus->phys +
535 (drb + size + 1) * CDMM_DRB_SIZE - 1;
536 dev->res.flags = IORESOURCE_MEM;
537 dev->type = type;
538 dev->rev = rev;
539 dev->dev.parent = get_cpu_device(cpu);
540 dev->dev.bus = &mips_cdmm_bustype;
541 dev->dev.id = atomic_inc_return(&mips_cdmm_next_id);
542 dev->dev.release = mips_cdmm_release;
543
544 dev_set_name(&dev->dev, "cdmm%u-%u", cpu, id);
545 ++id;
546 ret = device_register(&dev->dev);
547 if (ret) {
548 put_device(&dev->dev);
549 kfree(dev);
550 }
551 }
552 }
553
554
555 /*
556 * CPU hotplug and initialisation
557 *
558 * All the CDMM driver callbacks need to be executed on the appropriate CPU from
559 * workqueues. For the CPU callbacks, they need to be called for all devices on
560 * that CPU, so the work function calls bus_for_each_dev, using a helper
561 * (generated with BUILD_PERDEV_HELPER) to call the driver callback if the
562 * device's CPU matches.
563 */
564
565 /**
566 * BUILD_PERDEV_HELPER() - Helper to call a CDMM driver callback if CPU matches.
567 * @_name: Name of CDMM driver callback function.
568 *
569 * Generates a bus_for_each_dev callback function to call a specific CDMM driver
570 * callback function for the device if the device's CPU matches that pointed to
571 * by the data argument.
572 *
573 * This is used for informing drivers for all devices on a given CPU of some
574 * event (such as the CPU going online/offline).
575 *
576 * It is expected to already be called from the appropriate CPU.
577 */
578 #define BUILD_PERDEV_HELPER(_name) \
579 static int mips_cdmm_##_name##_helper(struct device *dev, void *data) \
580 { \
581 struct mips_cdmm_device *cdev = to_mips_cdmm_device(dev); \
582 struct mips_cdmm_driver *cdrv; \
583 unsigned int cpu = *(unsigned int *)data; \
584 \
585 if (cdev->cpu != cpu || !dev->driver) \
586 return 0; \
587 \
588 cdrv = to_mips_cdmm_driver(dev->driver); \
589 if (!cdrv->_name) \
590 return 0; \
591 return cdrv->_name(cdev); \
592 }
593
594 /* bus_for_each_dev callback helper functions */
595 BUILD_PERDEV_HELPER(cpu_down) /* int mips_cdmm_cpu_down_helper(...) */
596 BUILD_PERDEV_HELPER(cpu_up) /* int mips_cdmm_cpu_up_helper(...) */
597
598 /**
599 * mips_cdmm_cpu_down_prep() - Callback for CPUHP DOWN_PREP:
600 * Tear down the CDMM bus.
601 * @cpu: unsigned int CPU number.
602 *
603 * This function is executed on the hotplugged CPU and calls the CDMM
604 * driver cpu_down callback for all devices on that CPU.
605 */
606 static int mips_cdmm_cpu_down_prep(unsigned int cpu)
607 {
608 struct mips_cdmm_bus *bus;
609 long ret;
610
611 /* Inform all the devices on the bus */
612 ret = bus_for_each_dev(&mips_cdmm_bustype, NULL, &cpu,
613 mips_cdmm_cpu_down_helper);
614
615 /*
616 * While bus is offline, each use of it should reconfigure it just in
617 * case it is first use when coming back online again.
618 */
619 bus = mips_cdmm_get_bus();
620 if (!IS_ERR(bus))
621 bus->offline = true;
622
623 return ret;
624 }
625
626 /**
627 * mips_cdmm_cpu_online() - Callback for CPUHP ONLINE: Bring up the CDMM bus.
628 * @cpu: unsigned int CPU number.
629 *
630 * This work_on_cpu callback function is executed on a given CPU to discover
631 * CDMM devices on that CPU, or to call the CDMM driver cpu_up callback for all
632 * devices already discovered on that CPU.
633 *
634 * It is used as work_on_cpu callback function during
635 * initialisation. When CPUs are brought online the function is
636 * invoked directly on the hotplugged CPU.
637 */
638 static int mips_cdmm_cpu_online(unsigned int cpu)
639 {
640 struct mips_cdmm_bus *bus;
641 long ret;
642
643 bus = mips_cdmm_get_bus();
644 ret = mips_cdmm_setup(bus);
645 if (ret)
646 return ret;
647
648 /* Bus now set up, so we can drop the offline flag if still set */
649 bus->offline = false;
650
651 if (!bus->discovered)
652 mips_cdmm_bus_discover(bus);
653 else
654 /* Inform all the devices on the bus */
655 ret = bus_for_each_dev(&mips_cdmm_bustype, NULL, &cpu,
656 mips_cdmm_cpu_up_helper);
657
658 return ret;
659 }
660
661 /**
662 * mips_cdmm_init() - Initialise CDMM bus.
663 *
664 * Initialise CDMM bus, discover CDMM devices for online CPUs, and arrange for
665 * hotplug notifications so the CDMM drivers can be kept up to date.
666 */
667 static int __init mips_cdmm_init(void)
668 {
669 int ret;
670
671 /* Register the bus */
672 ret = bus_register(&mips_cdmm_bustype);
673 if (ret)
674 return ret;
675
676 /* We want to be notified about new CPUs */
677 ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "bus/cdmm:online",
678 mips_cdmm_cpu_online, mips_cdmm_cpu_down_prep);
679 if (ret < 0)
680 pr_warn("cdmm: Failed to register CPU notifier\n");
681
682 return ret;
683 }
684 subsys_initcall(mips_cdmm_init);