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