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