Merge tag 'jfs-6.3' of https://github.com/kleikamp/linux-shaggy
[linux-2.6-microblaze.git] / drivers / hwtracing / stm / core.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * System Trace Module (STM) infrastructure
4  * Copyright (c) 2014, Intel Corporation.
5  *
6  * STM class implements generic infrastructure for  System Trace Module devices
7  * as defined in MIPI STPv2 specification.
8  */
9
10 #include <linux/pm_runtime.h>
11 #include <linux/uaccess.h>
12 #include <linux/kernel.h>
13 #include <linux/module.h>
14 #include <linux/device.h>
15 #include <linux/compat.h>
16 #include <linux/kdev_t.h>
17 #include <linux/srcu.h>
18 #include <linux/slab.h>
19 #include <linux/stm.h>
20 #include <linux/fs.h>
21 #include <linux/mm.h>
22 #include <linux/vmalloc.h>
23 #include "stm.h"
24
25 #include <uapi/linux/stm.h>
26
27 static unsigned int stm_core_up;
28
29 /*
30  * The SRCU here makes sure that STM device doesn't disappear from under a
31  * stm_source_write() caller, which may want to have as little overhead as
32  * possible.
33  */
34 static struct srcu_struct stm_source_srcu;
35
36 static ssize_t masters_show(struct device *dev,
37                             struct device_attribute *attr,
38                             char *buf)
39 {
40         struct stm_device *stm = to_stm_device(dev);
41         int ret;
42
43         ret = sprintf(buf, "%u %u\n", stm->data->sw_start, stm->data->sw_end);
44
45         return ret;
46 }
47
48 static DEVICE_ATTR_RO(masters);
49
50 static ssize_t channels_show(struct device *dev,
51                              struct device_attribute *attr,
52                              char *buf)
53 {
54         struct stm_device *stm = to_stm_device(dev);
55         int ret;
56
57         ret = sprintf(buf, "%u\n", stm->data->sw_nchannels);
58
59         return ret;
60 }
61
62 static DEVICE_ATTR_RO(channels);
63
64 static ssize_t hw_override_show(struct device *dev,
65                                 struct device_attribute *attr,
66                                 char *buf)
67 {
68         struct stm_device *stm = to_stm_device(dev);
69         int ret;
70
71         ret = sprintf(buf, "%u\n", stm->data->hw_override);
72
73         return ret;
74 }
75
76 static DEVICE_ATTR_RO(hw_override);
77
78 static struct attribute *stm_attrs[] = {
79         &dev_attr_masters.attr,
80         &dev_attr_channels.attr,
81         &dev_attr_hw_override.attr,
82         NULL,
83 };
84
85 ATTRIBUTE_GROUPS(stm);
86
87 static struct class stm_class = {
88         .name           = "stm",
89         .dev_groups     = stm_groups,
90 };
91
92 /**
93  * stm_find_device() - find stm device by name
94  * @buf:        character buffer containing the name
95  *
96  * This is called when either policy gets assigned to an stm device or an
97  * stm_source device gets linked to an stm device.
98  *
99  * This grabs device's reference (get_device()) and module reference, both
100  * of which the calling path needs to make sure to drop with stm_put_device().
101  *
102  * Return:      stm device pointer or null if lookup failed.
103  */
104 struct stm_device *stm_find_device(const char *buf)
105 {
106         struct stm_device *stm;
107         struct device *dev;
108
109         if (!stm_core_up)
110                 return NULL;
111
112         dev = class_find_device_by_name(&stm_class, buf);
113         if (!dev)
114                 return NULL;
115
116         stm = to_stm_device(dev);
117         if (!try_module_get(stm->owner)) {
118                 /* matches class_find_device() above */
119                 put_device(dev);
120                 return NULL;
121         }
122
123         return stm;
124 }
125
126 /**
127  * stm_put_device() - drop references on the stm device
128  * @stm:        stm device, previously acquired by stm_find_device()
129  *
130  * This drops the module reference and device reference taken by
131  * stm_find_device() or stm_char_open().
132  */
133 void stm_put_device(struct stm_device *stm)
134 {
135         module_put(stm->owner);
136         put_device(&stm->dev);
137 }
138
139 /*
140  * Internally we only care about software-writable masters here, that is the
141  * ones in the range [stm_data->sw_start..stm_data..sw_end], however we need
142  * original master numbers to be visible externally, since they are the ones
143  * that will appear in the STP stream. Thus, the internal bookkeeping uses
144  * $master - stm_data->sw_start to reference master descriptors and such.
145  */
146
147 #define __stm_master(_s, _m)                            \
148         ((_s)->masters[(_m) - (_s)->data->sw_start])
149
150 static inline struct stp_master *
151 stm_master(struct stm_device *stm, unsigned int idx)
152 {
153         if (idx < stm->data->sw_start || idx > stm->data->sw_end)
154                 return NULL;
155
156         return __stm_master(stm, idx);
157 }
158
159 static int stp_master_alloc(struct stm_device *stm, unsigned int idx)
160 {
161         struct stp_master *master;
162
163         master = kzalloc(struct_size(master, chan_map,
164                                      BITS_TO_LONGS(stm->data->sw_nchannels)),
165                          GFP_ATOMIC);
166         if (!master)
167                 return -ENOMEM;
168
169         master->nr_free = stm->data->sw_nchannels;
170         __stm_master(stm, idx) = master;
171
172         return 0;
173 }
174
175 static void stp_master_free(struct stm_device *stm, unsigned int idx)
176 {
177         struct stp_master *master = stm_master(stm, idx);
178
179         if (!master)
180                 return;
181
182         __stm_master(stm, idx) = NULL;
183         kfree(master);
184 }
185
186 static void stm_output_claim(struct stm_device *stm, struct stm_output *output)
187 {
188         struct stp_master *master = stm_master(stm, output->master);
189
190         lockdep_assert_held(&stm->mc_lock);
191         lockdep_assert_held(&output->lock);
192
193         if (WARN_ON_ONCE(master->nr_free < output->nr_chans))
194                 return;
195
196         bitmap_allocate_region(&master->chan_map[0], output->channel,
197                                ilog2(output->nr_chans));
198
199         master->nr_free -= output->nr_chans;
200 }
201
202 static void
203 stm_output_disclaim(struct stm_device *stm, struct stm_output *output)
204 {
205         struct stp_master *master = stm_master(stm, output->master);
206
207         lockdep_assert_held(&stm->mc_lock);
208         lockdep_assert_held(&output->lock);
209
210         bitmap_release_region(&master->chan_map[0], output->channel,
211                               ilog2(output->nr_chans));
212
213         master->nr_free += output->nr_chans;
214         output->nr_chans = 0;
215 }
216
217 /*
218  * This is like bitmap_find_free_region(), except it can ignore @start bits
219  * at the beginning.
220  */
221 static int find_free_channels(unsigned long *bitmap, unsigned int start,
222                               unsigned int end, unsigned int width)
223 {
224         unsigned int pos;
225         int i;
226
227         for (pos = start; pos < end + 1; pos = ALIGN(pos, width)) {
228                 pos = find_next_zero_bit(bitmap, end + 1, pos);
229                 if (pos + width > end + 1)
230                         break;
231
232                 if (pos & (width - 1))
233                         continue;
234
235                 for (i = 1; i < width && !test_bit(pos + i, bitmap); i++)
236                         ;
237                 if (i == width)
238                         return pos;
239
240                 /* step over [pos..pos+i) to continue search */
241                 pos += i;
242         }
243
244         return -1;
245 }
246
247 static int
248 stm_find_master_chan(struct stm_device *stm, unsigned int width,
249                      unsigned int *mstart, unsigned int mend,
250                      unsigned int *cstart, unsigned int cend)
251 {
252         struct stp_master *master;
253         unsigned int midx;
254         int pos, err;
255
256         for (midx = *mstart; midx <= mend; midx++) {
257                 if (!stm_master(stm, midx)) {
258                         err = stp_master_alloc(stm, midx);
259                         if (err)
260                                 return err;
261                 }
262
263                 master = stm_master(stm, midx);
264
265                 if (!master->nr_free)
266                         continue;
267
268                 pos = find_free_channels(master->chan_map, *cstart, cend,
269                                          width);
270                 if (pos < 0)
271                         continue;
272
273                 *mstart = midx;
274                 *cstart = pos;
275                 return 0;
276         }
277
278         return -ENOSPC;
279 }
280
281 static int stm_output_assign(struct stm_device *stm, unsigned int width,
282                              struct stp_policy_node *policy_node,
283                              struct stm_output *output)
284 {
285         unsigned int midx, cidx, mend, cend;
286         int ret = -EINVAL;
287
288         if (width > stm->data->sw_nchannels)
289                 return -EINVAL;
290
291         /* We no longer accept policy_node==NULL here */
292         if (WARN_ON_ONCE(!policy_node))
293                 return -EINVAL;
294
295         /*
296          * Also, the caller holds reference to policy_node, so it won't
297          * disappear on us.
298          */
299         stp_policy_node_get_ranges(policy_node, &midx, &mend, &cidx, &cend);
300
301         spin_lock(&stm->mc_lock);
302         spin_lock(&output->lock);
303         /* output is already assigned -- shouldn't happen */
304         if (WARN_ON_ONCE(output->nr_chans))
305                 goto unlock;
306
307         ret = stm_find_master_chan(stm, width, &midx, mend, &cidx, cend);
308         if (ret < 0)
309                 goto unlock;
310
311         output->master = midx;
312         output->channel = cidx;
313         output->nr_chans = width;
314         if (stm->pdrv->output_open) {
315                 void *priv = stp_policy_node_priv(policy_node);
316
317                 if (WARN_ON_ONCE(!priv))
318                         goto unlock;
319
320                 /* configfs subsys mutex is held by the caller */
321                 ret = stm->pdrv->output_open(priv, output);
322                 if (ret)
323                         goto unlock;
324         }
325
326         stm_output_claim(stm, output);
327         dev_dbg(&stm->dev, "assigned %u:%u (+%u)\n", midx, cidx, width);
328
329         ret = 0;
330 unlock:
331         if (ret)
332                 output->nr_chans = 0;
333
334         spin_unlock(&output->lock);
335         spin_unlock(&stm->mc_lock);
336
337         return ret;
338 }
339
340 static void stm_output_free(struct stm_device *stm, struct stm_output *output)
341 {
342         spin_lock(&stm->mc_lock);
343         spin_lock(&output->lock);
344         if (output->nr_chans)
345                 stm_output_disclaim(stm, output);
346         if (stm->pdrv && stm->pdrv->output_close)
347                 stm->pdrv->output_close(output);
348         spin_unlock(&output->lock);
349         spin_unlock(&stm->mc_lock);
350 }
351
352 static void stm_output_init(struct stm_output *output)
353 {
354         spin_lock_init(&output->lock);
355 }
356
357 static int major_match(struct device *dev, const void *data)
358 {
359         unsigned int major = *(unsigned int *)data;
360
361         return MAJOR(dev->devt) == major;
362 }
363
364 /*
365  * Framing protocol management
366  * Modules can implement STM protocol drivers and (un-)register them
367  * with the STM class framework.
368  */
369 static struct list_head stm_pdrv_head;
370 static struct mutex stm_pdrv_mutex;
371
372 struct stm_pdrv_entry {
373         struct list_head                        entry;
374         const struct stm_protocol_driver        *pdrv;
375         const struct config_item_type           *node_type;
376 };
377
378 static const struct stm_pdrv_entry *
379 __stm_lookup_protocol(const char *name)
380 {
381         struct stm_pdrv_entry *pe;
382
383         /*
384          * If no name is given (NULL or ""), fall back to "p_basic".
385          */
386         if (!name || !*name)
387                 name = "p_basic";
388
389         list_for_each_entry(pe, &stm_pdrv_head, entry) {
390                 if (!strcmp(name, pe->pdrv->name))
391                         return pe;
392         }
393
394         return NULL;
395 }
396
397 int stm_register_protocol(const struct stm_protocol_driver *pdrv)
398 {
399         struct stm_pdrv_entry *pe = NULL;
400         int ret = -ENOMEM;
401
402         mutex_lock(&stm_pdrv_mutex);
403
404         if (__stm_lookup_protocol(pdrv->name)) {
405                 ret = -EEXIST;
406                 goto unlock;
407         }
408
409         pe = kzalloc(sizeof(*pe), GFP_KERNEL);
410         if (!pe)
411                 goto unlock;
412
413         if (pdrv->policy_attr) {
414                 pe->node_type = get_policy_node_type(pdrv->policy_attr);
415                 if (!pe->node_type)
416                         goto unlock;
417         }
418
419         list_add_tail(&pe->entry, &stm_pdrv_head);
420         pe->pdrv = pdrv;
421
422         ret = 0;
423 unlock:
424         mutex_unlock(&stm_pdrv_mutex);
425
426         if (ret)
427                 kfree(pe);
428
429         return ret;
430 }
431 EXPORT_SYMBOL_GPL(stm_register_protocol);
432
433 void stm_unregister_protocol(const struct stm_protocol_driver *pdrv)
434 {
435         struct stm_pdrv_entry *pe, *iter;
436
437         mutex_lock(&stm_pdrv_mutex);
438
439         list_for_each_entry_safe(pe, iter, &stm_pdrv_head, entry) {
440                 if (pe->pdrv == pdrv) {
441                         list_del(&pe->entry);
442
443                         if (pe->node_type) {
444                                 kfree(pe->node_type->ct_attrs);
445                                 kfree(pe->node_type);
446                         }
447                         kfree(pe);
448                         break;
449                 }
450         }
451
452         mutex_unlock(&stm_pdrv_mutex);
453 }
454 EXPORT_SYMBOL_GPL(stm_unregister_protocol);
455
456 static bool stm_get_protocol(const struct stm_protocol_driver *pdrv)
457 {
458         return try_module_get(pdrv->owner);
459 }
460
461 void stm_put_protocol(const struct stm_protocol_driver *pdrv)
462 {
463         module_put(pdrv->owner);
464 }
465
466 int stm_lookup_protocol(const char *name,
467                         const struct stm_protocol_driver **pdrv,
468                         const struct config_item_type **node_type)
469 {
470         const struct stm_pdrv_entry *pe;
471
472         mutex_lock(&stm_pdrv_mutex);
473
474         pe = __stm_lookup_protocol(name);
475         if (pe && pe->pdrv && stm_get_protocol(pe->pdrv)) {
476                 *pdrv = pe->pdrv;
477                 *node_type = pe->node_type;
478         }
479
480         mutex_unlock(&stm_pdrv_mutex);
481
482         return pe ? 0 : -ENOENT;
483 }
484
485 static int stm_char_open(struct inode *inode, struct file *file)
486 {
487         struct stm_file *stmf;
488         struct device *dev;
489         unsigned int major = imajor(inode);
490         int err = -ENOMEM;
491
492         dev = class_find_device(&stm_class, NULL, &major, major_match);
493         if (!dev)
494                 return -ENODEV;
495
496         stmf = kzalloc(sizeof(*stmf), GFP_KERNEL);
497         if (!stmf)
498                 goto err_put_device;
499
500         err = -ENODEV;
501         stm_output_init(&stmf->output);
502         stmf->stm = to_stm_device(dev);
503
504         if (!try_module_get(stmf->stm->owner))
505                 goto err_free;
506
507         file->private_data = stmf;
508
509         return nonseekable_open(inode, file);
510
511 err_free:
512         kfree(stmf);
513 err_put_device:
514         /* matches class_find_device() above */
515         put_device(dev);
516
517         return err;
518 }
519
520 static int stm_char_release(struct inode *inode, struct file *file)
521 {
522         struct stm_file *stmf = file->private_data;
523         struct stm_device *stm = stmf->stm;
524
525         if (stm->data->unlink)
526                 stm->data->unlink(stm->data, stmf->output.master,
527                                   stmf->output.channel);
528
529         stm_output_free(stm, &stmf->output);
530
531         /*
532          * matches the stm_char_open()'s
533          * class_find_device() + try_module_get()
534          */
535         stm_put_device(stm);
536         kfree(stmf);
537
538         return 0;
539 }
540
541 static int
542 stm_assign_first_policy(struct stm_device *stm, struct stm_output *output,
543                         char **ids, unsigned int width)
544 {
545         struct stp_policy_node *pn;
546         int err, n;
547
548         /*
549          * On success, stp_policy_node_lookup() will return holding the
550          * configfs subsystem mutex, which is then released in
551          * stp_policy_node_put(). This allows the pdrv->output_open() in
552          * stm_output_assign() to serialize against the attribute accessors.
553          */
554         for (n = 0, pn = NULL; ids[n] && !pn; n++)
555                 pn = stp_policy_node_lookup(stm, ids[n]);
556
557         if (!pn)
558                 return -EINVAL;
559
560         err = stm_output_assign(stm, width, pn, output);
561
562         stp_policy_node_put(pn);
563
564         return err;
565 }
566
567 /**
568  * stm_data_write() - send the given payload as data packets
569  * @data:       stm driver's data
570  * @m:          STP master
571  * @c:          STP channel
572  * @ts_first:   timestamp the first packet
573  * @buf:        data payload buffer
574  * @count:      data payload size
575  */
576 ssize_t notrace stm_data_write(struct stm_data *data, unsigned int m,
577                                unsigned int c, bool ts_first, const void *buf,
578                                size_t count)
579 {
580         unsigned int flags = ts_first ? STP_PACKET_TIMESTAMPED : 0;
581         ssize_t sz;
582         size_t pos;
583
584         for (pos = 0, sz = 0; pos < count; pos += sz) {
585                 sz = min_t(unsigned int, count - pos, 8);
586                 sz = data->packet(data, m, c, STP_PACKET_DATA, flags, sz,
587                                   &((u8 *)buf)[pos]);
588                 if (sz <= 0)
589                         break;
590
591                 if (ts_first) {
592                         flags = 0;
593                         ts_first = false;
594                 }
595         }
596
597         return sz < 0 ? sz : pos;
598 }
599 EXPORT_SYMBOL_GPL(stm_data_write);
600
601 static ssize_t notrace
602 stm_write(struct stm_device *stm, struct stm_output *output,
603           unsigned int chan, const char *buf, size_t count)
604 {
605         int err;
606
607         /* stm->pdrv is serialized against policy_mutex */
608         if (!stm->pdrv)
609                 return -ENODEV;
610
611         err = stm->pdrv->write(stm->data, output, chan, buf, count);
612         if (err < 0)
613                 return err;
614
615         return err;
616 }
617
618 static ssize_t stm_char_write(struct file *file, const char __user *buf,
619                               size_t count, loff_t *ppos)
620 {
621         struct stm_file *stmf = file->private_data;
622         struct stm_device *stm = stmf->stm;
623         char *kbuf;
624         int err;
625
626         if (count + 1 > PAGE_SIZE)
627                 count = PAGE_SIZE - 1;
628
629         /*
630          * If no m/c have been assigned to this writer up to this
631          * point, try to use the task name and "default" policy entries.
632          */
633         if (!stmf->output.nr_chans) {
634                 char comm[sizeof(current->comm)];
635                 char *ids[] = { comm, "default", NULL };
636
637                 get_task_comm(comm, current);
638
639                 err = stm_assign_first_policy(stmf->stm, &stmf->output, ids, 1);
640                 /*
641                  * EBUSY means that somebody else just assigned this
642                  * output, which is just fine for write()
643                  */
644                 if (err)
645                         return err;
646         }
647
648         kbuf = kmalloc(count + 1, GFP_KERNEL);
649         if (!kbuf)
650                 return -ENOMEM;
651
652         err = copy_from_user(kbuf, buf, count);
653         if (err) {
654                 kfree(kbuf);
655                 return -EFAULT;
656         }
657
658         pm_runtime_get_sync(&stm->dev);
659
660         count = stm_write(stm, &stmf->output, 0, kbuf, count);
661
662         pm_runtime_mark_last_busy(&stm->dev);
663         pm_runtime_put_autosuspend(&stm->dev);
664         kfree(kbuf);
665
666         return count;
667 }
668
669 static void stm_mmap_open(struct vm_area_struct *vma)
670 {
671         struct stm_file *stmf = vma->vm_file->private_data;
672         struct stm_device *stm = stmf->stm;
673
674         pm_runtime_get(&stm->dev);
675 }
676
677 static void stm_mmap_close(struct vm_area_struct *vma)
678 {
679         struct stm_file *stmf = vma->vm_file->private_data;
680         struct stm_device *stm = stmf->stm;
681
682         pm_runtime_mark_last_busy(&stm->dev);
683         pm_runtime_put_autosuspend(&stm->dev);
684 }
685
686 static const struct vm_operations_struct stm_mmap_vmops = {
687         .open   = stm_mmap_open,
688         .close  = stm_mmap_close,
689 };
690
691 static int stm_char_mmap(struct file *file, struct vm_area_struct *vma)
692 {
693         struct stm_file *stmf = file->private_data;
694         struct stm_device *stm = stmf->stm;
695         unsigned long size, phys;
696
697         if (!stm->data->mmio_addr)
698                 return -EOPNOTSUPP;
699
700         if (vma->vm_pgoff)
701                 return -EINVAL;
702
703         size = vma->vm_end - vma->vm_start;
704
705         if (stmf->output.nr_chans * stm->data->sw_mmiosz != size)
706                 return -EINVAL;
707
708         phys = stm->data->mmio_addr(stm->data, stmf->output.master,
709                                     stmf->output.channel,
710                                     stmf->output.nr_chans);
711
712         if (!phys)
713                 return -EINVAL;
714
715         pm_runtime_get_sync(&stm->dev);
716
717         vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
718         vm_flags_set(vma, VM_IO | VM_DONTEXPAND | VM_DONTDUMP);
719         vma->vm_ops = &stm_mmap_vmops;
720         vm_iomap_memory(vma, phys, size);
721
722         return 0;
723 }
724
725 static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg)
726 {
727         struct stm_device *stm = stmf->stm;
728         struct stp_policy_id *id;
729         char *ids[] = { NULL, NULL };
730         int ret = -EINVAL, wlimit = 1;
731         u32 size;
732
733         if (stmf->output.nr_chans)
734                 return -EBUSY;
735
736         if (copy_from_user(&size, arg, sizeof(size)))
737                 return -EFAULT;
738
739         if (size < sizeof(*id) || size >= PATH_MAX + sizeof(*id))
740                 return -EINVAL;
741
742         /*
743          * size + 1 to make sure the .id string at the bottom is terminated,
744          * which is also why memdup_user() is not useful here
745          */
746         id = kzalloc(size + 1, GFP_KERNEL);
747         if (!id)
748                 return -ENOMEM;
749
750         if (copy_from_user(id, arg, size)) {
751                 ret = -EFAULT;
752                 goto err_free;
753         }
754
755         if (id->__reserved_0 || id->__reserved_1)
756                 goto err_free;
757
758         if (stm->data->sw_mmiosz)
759                 wlimit = PAGE_SIZE / stm->data->sw_mmiosz;
760
761         if (id->width < 1 || id->width > wlimit)
762                 goto err_free;
763
764         ids[0] = id->id;
765         ret = stm_assign_first_policy(stmf->stm, &stmf->output, ids,
766                                       id->width);
767         if (ret)
768                 goto err_free;
769
770         if (stm->data->link)
771                 ret = stm->data->link(stm->data, stmf->output.master,
772                                       stmf->output.channel);
773
774         if (ret)
775                 stm_output_free(stmf->stm, &stmf->output);
776
777 err_free:
778         kfree(id);
779
780         return ret;
781 }
782
783 static int stm_char_policy_get_ioctl(struct stm_file *stmf, void __user *arg)
784 {
785         struct stp_policy_id id = {
786                 .size           = sizeof(id),
787                 .master         = stmf->output.master,
788                 .channel        = stmf->output.channel,
789                 .width          = stmf->output.nr_chans,
790                 .__reserved_0   = 0,
791                 .__reserved_1   = 0,
792         };
793
794         return copy_to_user(arg, &id, id.size) ? -EFAULT : 0;
795 }
796
797 static long
798 stm_char_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
799 {
800         struct stm_file *stmf = file->private_data;
801         struct stm_data *stm_data = stmf->stm->data;
802         int err = -ENOTTY;
803         u64 options;
804
805         switch (cmd) {
806         case STP_POLICY_ID_SET:
807                 err = stm_char_policy_set_ioctl(stmf, (void __user *)arg);
808                 if (err)
809                         return err;
810
811                 return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
812
813         case STP_POLICY_ID_GET:
814                 return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
815
816         case STP_SET_OPTIONS:
817                 if (copy_from_user(&options, (u64 __user *)arg, sizeof(u64)))
818                         return -EFAULT;
819
820                 if (stm_data->set_options)
821                         err = stm_data->set_options(stm_data,
822                                                     stmf->output.master,
823                                                     stmf->output.channel,
824                                                     stmf->output.nr_chans,
825                                                     options);
826
827                 break;
828         default:
829                 break;
830         }
831
832         return err;
833 }
834
835 static const struct file_operations stm_fops = {
836         .open           = stm_char_open,
837         .release        = stm_char_release,
838         .write          = stm_char_write,
839         .mmap           = stm_char_mmap,
840         .unlocked_ioctl = stm_char_ioctl,
841         .compat_ioctl   = compat_ptr_ioctl,
842         .llseek         = no_llseek,
843 };
844
845 static void stm_device_release(struct device *dev)
846 {
847         struct stm_device *stm = to_stm_device(dev);
848
849         vfree(stm);
850 }
851
852 int stm_register_device(struct device *parent, struct stm_data *stm_data,
853                         struct module *owner)
854 {
855         struct stm_device *stm;
856         unsigned int nmasters;
857         int err = -ENOMEM;
858
859         if (!stm_core_up)
860                 return -EPROBE_DEFER;
861
862         if (!stm_data->packet || !stm_data->sw_nchannels)
863                 return -EINVAL;
864
865         nmasters = stm_data->sw_end - stm_data->sw_start + 1;
866         stm = vzalloc(sizeof(*stm) + nmasters * sizeof(void *));
867         if (!stm)
868                 return -ENOMEM;
869
870         stm->major = register_chrdev(0, stm_data->name, &stm_fops);
871         if (stm->major < 0)
872                 goto err_free;
873
874         device_initialize(&stm->dev);
875         stm->dev.devt = MKDEV(stm->major, 0);
876         stm->dev.class = &stm_class;
877         stm->dev.parent = parent;
878         stm->dev.release = stm_device_release;
879
880         mutex_init(&stm->link_mutex);
881         spin_lock_init(&stm->link_lock);
882         INIT_LIST_HEAD(&stm->link_list);
883
884         /* initialize the object before it is accessible via sysfs */
885         spin_lock_init(&stm->mc_lock);
886         mutex_init(&stm->policy_mutex);
887         stm->sw_nmasters = nmasters;
888         stm->owner = owner;
889         stm->data = stm_data;
890         stm_data->stm = stm;
891
892         err = kobject_set_name(&stm->dev.kobj, "%s", stm_data->name);
893         if (err)
894                 goto err_device;
895
896         err = device_add(&stm->dev);
897         if (err)
898                 goto err_device;
899
900         /*
901          * Use delayed autosuspend to avoid bouncing back and forth
902          * on recurring character device writes, with the initial
903          * delay time of 2 seconds.
904          */
905         pm_runtime_no_callbacks(&stm->dev);
906         pm_runtime_use_autosuspend(&stm->dev);
907         pm_runtime_set_autosuspend_delay(&stm->dev, 2000);
908         pm_runtime_set_suspended(&stm->dev);
909         pm_runtime_enable(&stm->dev);
910
911         return 0;
912
913 err_device:
914         unregister_chrdev(stm->major, stm_data->name);
915
916         /* matches device_initialize() above */
917         put_device(&stm->dev);
918 err_free:
919         vfree(stm);
920
921         return err;
922 }
923 EXPORT_SYMBOL_GPL(stm_register_device);
924
925 static int __stm_source_link_drop(struct stm_source_device *src,
926                                   struct stm_device *stm);
927
928 void stm_unregister_device(struct stm_data *stm_data)
929 {
930         struct stm_device *stm = stm_data->stm;
931         struct stm_source_device *src, *iter;
932         int i, ret;
933
934         pm_runtime_dont_use_autosuspend(&stm->dev);
935         pm_runtime_disable(&stm->dev);
936
937         mutex_lock(&stm->link_mutex);
938         list_for_each_entry_safe(src, iter, &stm->link_list, link_entry) {
939                 ret = __stm_source_link_drop(src, stm);
940                 /*
941                  * src <-> stm link must not change under the same
942                  * stm::link_mutex, so complain loudly if it has;
943                  * also in this situation ret!=0 means this src is
944                  * not connected to this stm and it should be otherwise
945                  * safe to proceed with the tear-down of stm.
946                  */
947                 WARN_ON_ONCE(ret);
948         }
949         mutex_unlock(&stm->link_mutex);
950
951         synchronize_srcu(&stm_source_srcu);
952
953         unregister_chrdev(stm->major, stm_data->name);
954
955         mutex_lock(&stm->policy_mutex);
956         if (stm->policy)
957                 stp_policy_unbind(stm->policy);
958         mutex_unlock(&stm->policy_mutex);
959
960         for (i = stm->data->sw_start; i <= stm->data->sw_end; i++)
961                 stp_master_free(stm, i);
962
963         device_unregister(&stm->dev);
964         stm_data->stm = NULL;
965 }
966 EXPORT_SYMBOL_GPL(stm_unregister_device);
967
968 /*
969  * stm::link_list access serialization uses a spinlock and a mutex; holding
970  * either of them guarantees that the list is stable; modification requires
971  * holding both of them.
972  *
973  * Lock ordering is as follows:
974  *   stm::link_mutex
975  *     stm::link_lock
976  *       src::link_lock
977  */
978
979 /**
980  * stm_source_link_add() - connect an stm_source device to an stm device
981  * @src:        stm_source device
982  * @stm:        stm device
983  *
984  * This function establishes a link from stm_source to an stm device so that
985  * the former can send out trace data to the latter.
986  *
987  * Return:      0 on success, -errno otherwise.
988  */
989 static int stm_source_link_add(struct stm_source_device *src,
990                                struct stm_device *stm)
991 {
992         char *ids[] = { NULL, "default", NULL };
993         int err = -ENOMEM;
994
995         mutex_lock(&stm->link_mutex);
996         spin_lock(&stm->link_lock);
997         spin_lock(&src->link_lock);
998
999         /* src->link is dereferenced under stm_source_srcu but not the list */
1000         rcu_assign_pointer(src->link, stm);
1001         list_add_tail(&src->link_entry, &stm->link_list);
1002
1003         spin_unlock(&src->link_lock);
1004         spin_unlock(&stm->link_lock);
1005         mutex_unlock(&stm->link_mutex);
1006
1007         ids[0] = kstrdup(src->data->name, GFP_KERNEL);
1008         if (!ids[0])
1009                 goto fail_detach;
1010
1011         err = stm_assign_first_policy(stm, &src->output, ids,
1012                                       src->data->nr_chans);
1013         kfree(ids[0]);
1014
1015         if (err)
1016                 goto fail_detach;
1017
1018         /* this is to notify the STM device that a new link has been made */
1019         if (stm->data->link)
1020                 err = stm->data->link(stm->data, src->output.master,
1021                                       src->output.channel);
1022
1023         if (err)
1024                 goto fail_free_output;
1025
1026         /* this is to let the source carry out all necessary preparations */
1027         if (src->data->link)
1028                 src->data->link(src->data);
1029
1030         return 0;
1031
1032 fail_free_output:
1033         stm_output_free(stm, &src->output);
1034
1035 fail_detach:
1036         mutex_lock(&stm->link_mutex);
1037         spin_lock(&stm->link_lock);
1038         spin_lock(&src->link_lock);
1039
1040         rcu_assign_pointer(src->link, NULL);
1041         list_del_init(&src->link_entry);
1042
1043         spin_unlock(&src->link_lock);
1044         spin_unlock(&stm->link_lock);
1045         mutex_unlock(&stm->link_mutex);
1046
1047         return err;
1048 }
1049
1050 /**
1051  * __stm_source_link_drop() - detach stm_source from an stm device
1052  * @src:        stm_source device
1053  * @stm:        stm device
1054  *
1055  * If @stm is @src::link, disconnect them from one another and put the
1056  * reference on the @stm device.
1057  *
1058  * Caller must hold stm::link_mutex.
1059  */
1060 static int __stm_source_link_drop(struct stm_source_device *src,
1061                                   struct stm_device *stm)
1062 {
1063         struct stm_device *link;
1064         int ret = 0;
1065
1066         lockdep_assert_held(&stm->link_mutex);
1067
1068         /* for stm::link_list modification, we hold both mutex and spinlock */
1069         spin_lock(&stm->link_lock);
1070         spin_lock(&src->link_lock);
1071         link = srcu_dereference_check(src->link, &stm_source_srcu, 1);
1072
1073         /*
1074          * The linked device may have changed since we last looked, because
1075          * we weren't holding the src::link_lock back then; if this is the
1076          * case, tell the caller to retry.
1077          */
1078         if (link != stm) {
1079                 ret = -EAGAIN;
1080                 goto unlock;
1081         }
1082
1083         stm_output_free(link, &src->output);
1084         list_del_init(&src->link_entry);
1085         pm_runtime_mark_last_busy(&link->dev);
1086         pm_runtime_put_autosuspend(&link->dev);
1087         /* matches stm_find_device() from stm_source_link_store() */
1088         stm_put_device(link);
1089         rcu_assign_pointer(src->link, NULL);
1090
1091 unlock:
1092         spin_unlock(&src->link_lock);
1093         spin_unlock(&stm->link_lock);
1094
1095         /*
1096          * Call the unlink callbacks for both source and stm, when we know
1097          * that we have actually performed the unlinking.
1098          */
1099         if (!ret) {
1100                 if (src->data->unlink)
1101                         src->data->unlink(src->data);
1102
1103                 if (stm->data->unlink)
1104                         stm->data->unlink(stm->data, src->output.master,
1105                                           src->output.channel);
1106         }
1107
1108         return ret;
1109 }
1110
1111 /**
1112  * stm_source_link_drop() - detach stm_source from its stm device
1113  * @src:        stm_source device
1114  *
1115  * Unlinking means disconnecting from source's STM device; after this
1116  * writes will be unsuccessful until it is linked to a new STM device.
1117  *
1118  * This will happen on "stm_source_link" sysfs attribute write to undo
1119  * the existing link (if any), or on linked STM device's de-registration.
1120  */
1121 static void stm_source_link_drop(struct stm_source_device *src)
1122 {
1123         struct stm_device *stm;
1124         int idx, ret;
1125
1126 retry:
1127         idx = srcu_read_lock(&stm_source_srcu);
1128         /*
1129          * The stm device will be valid for the duration of this
1130          * read section, but the link may change before we grab
1131          * the src::link_lock in __stm_source_link_drop().
1132          */
1133         stm = srcu_dereference(src->link, &stm_source_srcu);
1134
1135         ret = 0;
1136         if (stm) {
1137                 mutex_lock(&stm->link_mutex);
1138                 ret = __stm_source_link_drop(src, stm);
1139                 mutex_unlock(&stm->link_mutex);
1140         }
1141
1142         srcu_read_unlock(&stm_source_srcu, idx);
1143
1144         /* if it did change, retry */
1145         if (ret == -EAGAIN)
1146                 goto retry;
1147 }
1148
1149 static ssize_t stm_source_link_show(struct device *dev,
1150                                     struct device_attribute *attr,
1151                                     char *buf)
1152 {
1153         struct stm_source_device *src = to_stm_source_device(dev);
1154         struct stm_device *stm;
1155         int idx, ret;
1156
1157         idx = srcu_read_lock(&stm_source_srcu);
1158         stm = srcu_dereference(src->link, &stm_source_srcu);
1159         ret = sprintf(buf, "%s\n",
1160                       stm ? dev_name(&stm->dev) : "<none>");
1161         srcu_read_unlock(&stm_source_srcu, idx);
1162
1163         return ret;
1164 }
1165
1166 static ssize_t stm_source_link_store(struct device *dev,
1167                                      struct device_attribute *attr,
1168                                      const char *buf, size_t count)
1169 {
1170         struct stm_source_device *src = to_stm_source_device(dev);
1171         struct stm_device *link;
1172         int err;
1173
1174         stm_source_link_drop(src);
1175
1176         link = stm_find_device(buf);
1177         if (!link)
1178                 return -EINVAL;
1179
1180         pm_runtime_get(&link->dev);
1181
1182         err = stm_source_link_add(src, link);
1183         if (err) {
1184                 pm_runtime_put_autosuspend(&link->dev);
1185                 /* matches the stm_find_device() above */
1186                 stm_put_device(link);
1187         }
1188
1189         return err ? : count;
1190 }
1191
1192 static DEVICE_ATTR_RW(stm_source_link);
1193
1194 static struct attribute *stm_source_attrs[] = {
1195         &dev_attr_stm_source_link.attr,
1196         NULL,
1197 };
1198
1199 ATTRIBUTE_GROUPS(stm_source);
1200
1201 static struct class stm_source_class = {
1202         .name           = "stm_source",
1203         .dev_groups     = stm_source_groups,
1204 };
1205
1206 static void stm_source_device_release(struct device *dev)
1207 {
1208         struct stm_source_device *src = to_stm_source_device(dev);
1209
1210         kfree(src);
1211 }
1212
1213 /**
1214  * stm_source_register_device() - register an stm_source device
1215  * @parent:     parent device
1216  * @data:       device description structure
1217  *
1218  * This will create a device of stm_source class that can write
1219  * data to an stm device once linked.
1220  *
1221  * Return:      0 on success, -errno otherwise.
1222  */
1223 int stm_source_register_device(struct device *parent,
1224                                struct stm_source_data *data)
1225 {
1226         struct stm_source_device *src;
1227         int err;
1228
1229         if (!stm_core_up)
1230                 return -EPROBE_DEFER;
1231
1232         src = kzalloc(sizeof(*src), GFP_KERNEL);
1233         if (!src)
1234                 return -ENOMEM;
1235
1236         device_initialize(&src->dev);
1237         src->dev.class = &stm_source_class;
1238         src->dev.parent = parent;
1239         src->dev.release = stm_source_device_release;
1240
1241         err = kobject_set_name(&src->dev.kobj, "%s", data->name);
1242         if (err)
1243                 goto err;
1244
1245         pm_runtime_no_callbacks(&src->dev);
1246         pm_runtime_forbid(&src->dev);
1247
1248         err = device_add(&src->dev);
1249         if (err)
1250                 goto err;
1251
1252         stm_output_init(&src->output);
1253         spin_lock_init(&src->link_lock);
1254         INIT_LIST_HEAD(&src->link_entry);
1255         src->data = data;
1256         data->src = src;
1257
1258         return 0;
1259
1260 err:
1261         put_device(&src->dev);
1262
1263         return err;
1264 }
1265 EXPORT_SYMBOL_GPL(stm_source_register_device);
1266
1267 /**
1268  * stm_source_unregister_device() - unregister an stm_source device
1269  * @data:       device description that was used to register the device
1270  *
1271  * This will remove a previously created stm_source device from the system.
1272  */
1273 void stm_source_unregister_device(struct stm_source_data *data)
1274 {
1275         struct stm_source_device *src = data->src;
1276
1277         stm_source_link_drop(src);
1278
1279         device_unregister(&src->dev);
1280 }
1281 EXPORT_SYMBOL_GPL(stm_source_unregister_device);
1282
1283 int notrace stm_source_write(struct stm_source_data *data,
1284                              unsigned int chan,
1285                              const char *buf, size_t count)
1286 {
1287         struct stm_source_device *src = data->src;
1288         struct stm_device *stm;
1289         int idx;
1290
1291         if (!src->output.nr_chans)
1292                 return -ENODEV;
1293
1294         if (chan >= src->output.nr_chans)
1295                 return -EINVAL;
1296
1297         idx = srcu_read_lock(&stm_source_srcu);
1298
1299         stm = srcu_dereference(src->link, &stm_source_srcu);
1300         if (stm)
1301                 count = stm_write(stm, &src->output, chan, buf, count);
1302         else
1303                 count = -ENODEV;
1304
1305         srcu_read_unlock(&stm_source_srcu, idx);
1306
1307         return count;
1308 }
1309 EXPORT_SYMBOL_GPL(stm_source_write);
1310
1311 static int __init stm_core_init(void)
1312 {
1313         int err;
1314
1315         err = class_register(&stm_class);
1316         if (err)
1317                 return err;
1318
1319         err = class_register(&stm_source_class);
1320         if (err)
1321                 goto err_stm;
1322
1323         err = stp_configfs_init();
1324         if (err)
1325                 goto err_src;
1326
1327         init_srcu_struct(&stm_source_srcu);
1328         INIT_LIST_HEAD(&stm_pdrv_head);
1329         mutex_init(&stm_pdrv_mutex);
1330
1331         /*
1332          * So as to not confuse existing users with a requirement
1333          * to load yet another module, do it here.
1334          */
1335         if (IS_ENABLED(CONFIG_STM_PROTO_BASIC))
1336                 (void)request_module_nowait("stm_p_basic");
1337         stm_core_up++;
1338
1339         return 0;
1340
1341 err_src:
1342         class_unregister(&stm_source_class);
1343 err_stm:
1344         class_unregister(&stm_class);
1345
1346         return err;
1347 }
1348
1349 module_init(stm_core_init);
1350
1351 static void __exit stm_core_exit(void)
1352 {
1353         cleanup_srcu_struct(&stm_source_srcu);
1354         class_unregister(&stm_source_class);
1355         class_unregister(&stm_class);
1356         stp_configfs_exit();
1357 }
1358
1359 module_exit(stm_core_exit);
1360
1361 MODULE_LICENSE("GPL v2");
1362 MODULE_DESCRIPTION("System Trace Module device class");
1363 MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");