summaryrefslogtreecommitdiffstats
path: root/drivers/gpu/drm/xen/xen_drm_front.c
blob: 0d8e6bd1ccbf207d0dd2e276ae7d19adf704d006 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
// SPDX-License-Identifier: GPL-2.0 OR MIT

/*
 *  Xen para-virtual DRM device
 *
 * Copyright (C) 2016-2018 EPAM Systems Inc.
 *
 * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
 */

#include <linux/delay.h>
#include <linux/dma-mapping.h>
#include <linux/module.h>
#include <linux/of_device.h>

#include <drm/drm_atomic_helper.h>
#include <drm/drm_drv.h>
#include <drm/drm_ioctl.h>
#include <drm/drm_probe_helper.h>
#include <drm/drm_file.h>
#include <drm/drm_gem.h>

#include <xen/platform_pci.h>
#include <xen/xen.h>
#include <xen/xenbus.h>

#include <xen/xen-front-pgdir-shbuf.h>
#include <xen/interface/io/displif.h>

#include "xen_drm_front.h"
#include "xen_drm_front_cfg.h"
#include "xen_drm_front_evtchnl.h"
#include "xen_drm_front_gem.h"
#include "xen_drm_front_kms.h"

struct xen_drm_front_dbuf {
	struct list_head list;
	u64 dbuf_cookie;
	u64 fb_cookie;

	struct xen_front_pgdir_shbuf shbuf;
};

static void dbuf_add_to_list(struct xen_drm_front_info *front_info,
			     struct xen_drm_front_dbuf *dbuf, u64 dbuf_cookie)
{
	dbuf->dbuf_cookie = dbuf_cookie;
	list_add(&dbuf->list, &front_info->dbuf_list);
}

static struct xen_drm_front_dbuf *dbuf_get(struct list_head *dbuf_list,
					   u64 dbuf_cookie)
{
	struct xen_drm_front_dbuf *buf, *q;

	list_for_each_entry_safe(buf, q, dbuf_list, list)
		if (buf->dbuf_cookie == dbuf_cookie)
			return buf;

	return NULL;
}

static void dbuf_free(struct list_head *dbuf_list, u64 dbuf_cookie)
{
	struct xen_drm_front_dbuf *buf, *q;

	list_for_each_entry_safe(buf, q, dbuf_list, list)
		if (buf->dbuf_cookie == dbuf_cookie) {
			list_del(&buf->list);
			xen_front_pgdir_shbuf_unmap(&buf->shbuf);
			xen_front_pgdir_shbuf_free(&buf->shbuf);
			kfree(buf);
			break;
		}
}

static void dbuf_free_all(struct list_head *dbuf_list)
{
	struct xen_drm_front_dbuf *buf, *q;

	list_for_each_entry_safe(buf, q, dbuf_list, list) {
		list_del(&buf->list);
		xen_front_pgdir_shbuf_unmap(&buf->shbuf);
		xen_front_pgdir_shbuf_free(&buf->shbuf);
		kfree(buf);
	}
}

static struct xendispl_req *
be_prepare_req(struct xen_drm_front_evtchnl *evtchnl, u8 operation)
{
	struct xendispl_req *req;

	req = RING_GET_REQUEST(&evtchnl->u.req.ring,
			       evtchnl->u.req.ring.req_prod_pvt);
	req->operation = operation;
	req->id = evtchnl->evt_next_id++;
	evtchnl->evt_id = req->id;
	return req;
}

static int be_stream_do_io(struct xen_drm_front_evtchnl *evtchnl,
			   struct xendispl_req *req)
{
	reinit_completion(&evtchnl->u.req.completion);
	if (unlikely(evtchnl->state != EVTCHNL_STATE_CONNECTED))
		return -EIO;

	xen_drm_front_evtchnl_flush(evtchnl);
	return 0;
}

static int be_stream_wait_io(struct xen_drm_front_evtchnl *evtchnl)
{
	if (wait_for_completion_timeout(&evtchnl->u.req.completion,
			msecs_to_jiffies(XEN_DRM_FRONT_WAIT_BACK_MS)) <= 0)
		return -ETIMEDOUT;

	return evtchnl->u.req.resp_status;
}

int xen_drm_front_mode_set(struct xen_drm_front_drm_pipeline *pipeline,
			   u32 x, u32 y, u32 width, u32 height,
			   u32 bpp, u64 fb_cookie)
{
	struct xen_drm_front_evtchnl *evtchnl;
	struct xen_drm_front_info *front_info;
	struct xendispl_req *req;
	unsigned long flags;
	int ret;

	front_info = pipeline->drm_info->front_info;
	evtchnl = &front_info->evt_pairs[pipeline->index].req;
	if (unlikely(!evtchnl))
		return -EIO;

	mutex_lock(&evtchnl->u.req.req_io_lock);

	spin_lock_irqsave(&front_info->io_lock, flags);
	req = be_prepare_req(evtchnl, XENDISPL_OP_SET_CONFIG);
	req->op.set_config.x = x;
	req->op.set_config.y = y;
	req->op.set_config.width = width;
	req->op.set_config.height = height;
	req->op.set_config.bpp = bpp;
	req->op.set_config.fb_cookie = fb_cookie;

	ret = be_stream_do_io(evtchnl, req);
	spin_unlock_irqrestore(&front_info->io_lock, flags);

	if (ret == 0)
		ret = be_stream_wait_io(evtchnl);

	mutex_unlock(&evtchnl->u.req.req_io_lock);
	return ret;
}

int xen_drm_front_dbuf_create(struct xen_drm_front_info *front_info,
			      u64 dbuf_cookie, u32 width, u32 height,
			      u32 bpp, u64 size, u32 offset,
			      struct page **pages)
{
	struct xen_drm_front_evtchnl *evtchnl;
	struct xen_drm_front_dbuf *dbuf;
	struct xendispl_req *req;
	struct xen_front_pgdir_shbuf_cfg buf_cfg;
	unsigned long flags;
	int ret;

	evtchnl = &front_info->evt_pairs[GENERIC_OP_EVT_CHNL].req;
	if (unlikely(!evtchnl))
		return -EIO;

	dbuf = kzalloc(sizeof(*dbuf), GFP_KERNEL);
	if (!dbuf)
		return -ENOMEM;

	dbuf_add_to_list(front_info, dbuf, dbuf_cookie);

	memset(&buf_cfg, 0, sizeof(buf_cfg));
	buf_cfg.xb_dev = front_info->xb_dev;
	buf_cfg.num_pages = DIV_ROUND_UP(size, PAGE_SIZE);
	buf_cfg.pages = pages;
	buf_cfg.pgdir = &dbuf->shbuf;
	buf_cfg.be_alloc = front_info->cfg.be_alloc;

	ret = xen_front_pgdir_shbuf_alloc(&buf_cfg);
	if (ret < 0)
		goto fail_shbuf_alloc;

	mutex_lock(&evtchnl->u.req.req_io_lock);

	spin_lock_irqsave(&front_info->io_lock, flags);
	req = be_prepare_req(evtchnl, XENDISPL_OP_DBUF_CREATE);
	req->op.dbuf_create.gref_directory =
			xen_front_pgdir_shbuf_get_dir_start(&dbuf->shbuf);
	req->op.dbuf_create.buffer_sz = size;
	req->op.dbuf_create.data_ofs = offset;
	req->op.dbuf_create.dbuf_cookie = dbuf_cookie;
	req->op.dbuf_create.width = width;
	req->op.dbuf_create.height = height;
	req->op.dbuf_create.bpp = bpp;
	if (buf_cfg.be_alloc)
		req->op.dbuf_create.flags |= XENDISPL_DBUF_FLG_REQ_ALLOC;

	ret = be_stream_do_io(evtchnl, req);
	spin_unlock_irqrestore(&front_info->io_lock, flags);

	if (ret < 0)
		goto fail;

	ret = be_stream_wait_io(evtchnl);
	if (ret < 0)
		goto fail;

	ret = xen_front_pgdir_shbuf_map(&dbuf->shbuf);
	if (ret < 0)
		goto fail;

	mutex_unlock(&evtchnl->u.req.req_io_lock);
	return 0;

fail:
	mutex_unlock(&evtchnl->u.req.req_io_lock);
fail_shbuf_alloc:
	dbuf_free(&front_info->dbuf_list, dbuf_cookie);
	return ret;
}

static int xen_drm_front_dbuf_destroy(struct xen_drm_front_info *front_info,
				      u64 dbuf_cookie)
{
	struct xen_drm_front_evtchnl *evtchnl;
	struct xendispl_req *req;
	unsigned long flags;
	bool be_alloc;
	int ret;

	evtchnl = &front_info->evt_pairs[GENERIC_OP_EVT_CHNL].req;
	if (unlikely(!evtchnl))
		return -EIO;

	be_alloc = front_info->cfg.be_alloc;

	/*
	 * For the backend allocated buffer release references now, so backend
	 * can free the buffer.
	 */
	if (be_alloc)
		dbuf_free(&front_info->dbuf_list, dbuf_cookie);

	mutex_lock(&evtchnl->u.req.req_io_lock);

	spin_lock_irqsave(&front_info->io_lock, flags);
	req = be_prepare_req(evtchnl, XENDISPL_OP_DBUF_DESTROY);
	req->op.dbuf_destroy.dbuf_cookie = dbuf_cookie;

	ret = be_stream_do_io(evtchnl, req);
	spin_unlock_irqrestore(&front_info->io_lock, flags);

	if (ret == 0)
		ret = be_stream_wait_io(evtchnl);

	/*
	 * Do this regardless of communication status with the backend:
	 * if we cannot remove remote resources remove what we can locally.
	 */
	if (!be_alloc)
		dbuf_free(&front_info->dbuf_list, dbuf_cookie);

	mutex_unlock(&evtchnl->u.req.req_io_lock);
	return ret;
}

int xen_drm_front_fb_attach(struct xen_drm_front_info *front_info,
			    u64 dbuf_cookie, u64 fb_cookie, u32 width,
			    u32 height, u32 pixel_format)
{
	struct xen_drm_front_evtchnl *evtchnl;
	struct xen_drm_front_dbuf *buf;
	struct xendispl_req *req;
	unsigned long flags;
	int ret;

	evtchnl = &front_info->evt_pairs[GENERIC_OP_EVT_CHNL].req;
	if (unlikely(!evtchnl))
		return -EIO;

	buf = dbuf_get(&front_info->dbuf_list, dbuf_cookie);
	if (!buf)
		return -EINVAL;

	buf->fb_cookie = fb_cookie;

	mutex_lock(&evtchnl->u.req.req_io_lock);

	spin_lock_irqsave(&front_info->io_lock, flags);
	req = be_prepare_req(evtchnl, XENDISPL_OP_FB_ATTACH);
	req->op.fb_attach.dbuf_cookie = dbuf_cookie;
	req->op.fb_attach.fb_cookie = fb_cookie;
	req->op.fb_attach.width = width;
	req->op.fb_attach.height = height;
	req->op.fb_attach.pixel_format = pixel_format;

	ret = be_stream_do_io(evtchnl, req);
	spin_unlock_irqrestore(&front_info->io_lock, flags);

	if (ret == 0)
		ret = be_stream_wait_io(evtchnl);

	mutex_unlock(&evtchnl->u.req.req_io_lock);
	return ret;
}

int xen_drm_front_fb_detach(struct xen_drm_front_info *front_info,
			    u64 fb_cookie)
{
	struct xen_drm_front_evtchnl *evtchnl;
	struct xendispl_req *req;
	unsigned long flags;
	int ret;

	evtchnl = &front_info->evt_pairs[GENERIC_OP_EVT_CHNL].req;
	if (unlikely(!evtchnl))
		return -EIO;

	mutex_lock(&evtchnl->u.req.req_io_lock);

	spin_lock_irqsave(&front_info->io_lock, flags);
	req = be_prepare_req(evtchnl, XENDISPL_OP_FB_DETACH);
	req->op.fb_detach.fb_cookie = fb_cookie;

	ret = be_stream_do_io(evtchnl, req);
	spin_unlock_irqrestore(&front_info->io_lock, flags);

	if (ret == 0)
		ret = be_stream_wait_io(evtchnl);

	mutex_unlock(&evtchnl->u.req.req_io_lock);
	return ret;
}

int xen_drm_front_page_flip(struct xen_drm_front_info *front_info,
			    int conn_idx, u64 fb_cookie)
{
	struct xen_drm_front_evtchnl *evtchnl;
	struct xendispl_req *req;
	unsigned long flags;
	int ret;

	if (unlikely(conn_idx >= front_info->num_evt_pairs))
		return -EINVAL;

	evtchnl = &front_info->evt_pairs[conn_idx].req;

	mutex_lock(&evtchnl->u.req.req_io_lock);

	spin_lock_irqsave(&front_info->io_lock, flags);
	req = be_prepare_req(evtchnl, XENDISPL_OP_PG_FLIP);
	req->op.pg_flip.fb_cookie = fb_cookie;

	ret = be_stream_do_io(evtchnl, req);
	spin_unlock_irqrestore(&front_info->io_lock, flags);

	if (ret == 0)
		ret = be_stream_wait_io(evtchnl);

	mutex_unlock(&evtchnl->u.req.req_io_lock);
	return ret;
}

void xen_drm_front_on_frame_done(struct xen_drm_front_info *front_info,
				 int conn_idx, u64 fb_cookie)
{
	struct xen_drm_front_drm_info *drm_info = front_info->drm_info;

	if (unlikely(conn_idx >= front_info->cfg.num_connectors))
		return;

	xen_drm_front_kms_on_frame_done(&drm_info->pipeline[conn_idx],
					fb_cookie);
}

void xen_drm_front_gem_object_free(struct drm_gem_object *obj)
{
	struct xen_drm_front_drm_info *drm_info = obj->dev->dev_private;
	int idx;

	if (drm_dev_enter(obj->dev, &idx)) {
		xen_drm_front_dbuf_destroy(drm_info->front_info,
					   xen_drm_front_dbuf_to_cookie(obj));
		drm_dev_exit(idx);
	} else {
		dbuf_free(&drm_info->front_info->dbuf_list,
			  xen_drm_front_dbuf_to_cookie(obj));
	}

	xen_drm_front_gem_free_object_unlocked(obj);
}

static int xen_drm_drv_dumb_create(struct drm_file *filp,
				   struct drm_device *dev,
				   struct drm_mode_create_dumb *args)
{
	struct xen_drm_front_drm_info *drm_info = dev->dev_private;
	struct drm_gem_object *obj;
	int ret;

	/*
	 * Dumb creation is a two stage process: first we create a fully
	 * constructed GEM object which is communicated to the backend, and
	 * only after that we can create GEM's handle. This is done so,
	 * because of the possible races: once you create a handle it becomes
	 * immediately visible to user-space, so the latter can try accessing
	 * object without pages etc.
	 * For details also see drm_gem_handle_create
	 */
	args->pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
	args->size = args->pitch * args->height;

	obj = xen_drm_front_gem_create(dev, args->size);
	if (IS_ERR(obj)) {
		ret = PTR_ERR(obj);
		goto fail;
	}

	ret = xen_drm_front_dbuf_create(drm_info->front_info,
					xen_drm_front_dbuf_to_cookie(obj),
					args->width, args->height, args->bpp,
					args->size, 0,
					xen_drm_front_gem_get_pages(obj));
	if (ret)
		goto fail_backend;

	/* This is the tail of GEM object creation */
	ret = drm_gem_handle_create(filp, obj, &args->handle);
	if (ret)
		goto fail_handle;

	/* Drop reference from allocate - handle holds it now */
	drm_gem_object_put(obj);
	return 0;

fail_handle:
	xen_drm_front_dbuf_destroy(drm_info->front_info,
				   xen_drm_front_dbuf_to_cookie(obj));
fail_backend:
	/* drop reference from allocate */
	drm_gem_object_put(obj);
fail:
	DRM_ERROR("Failed to create dumb buffer: %d\n", ret);
	return ret;
}

static void xen_drm_drv_release(struct drm_device *dev)
{
	struct xen_drm_front_drm_info *drm_info = dev->dev_private;
	struct xen_drm_front_info *front_info = drm_info->front_info;

	xen_drm_front_kms_fini(drm_info);

	drm_atomic_helper_shutdown(dev);
	drm_mode_config_cleanup(dev);

	if (front_info->cfg.be_alloc)
		xenbus_switch_state(front_info->xb_dev,
				    XenbusStateInitialising);

	kfree(drm_info);
}

DEFINE_DRM_GEM_FOPS(xen_drm_dev_fops);

static const struct drm_driver xen_drm_driver = {
	.driver_features           = DRIVER_GEM | DRIVER_MODESET | DRIVER_ATOMIC,
	.release                   = xen_drm_drv_release,
	.prime_handle_to_fd        = drm_gem_prime_handle_to_fd,
	.prime_fd_to_handle        = drm_gem_prime_fd_to_handle,
	.gem_prime_import_sg_table = xen_drm_front_gem_import_sg_table,
	.gem_prime_mmap            = drm_gem_prime_mmap,
	.dumb_create               = xen_drm_drv_dumb_create,
	.fops                      = &xen_drm_dev_fops,
	.name                      = "xendrm-du",
	.desc                      = "Xen PV DRM Display Unit",
	.date                      = "20180221",
	.major                     = 1,
	.minor                     = 0,

};

static int xen_drm_drv_init(struct xen_drm_front_info *front_info)
{
	struct device *dev = &front_info->xb_dev->dev;
	struct xen_drm_front_drm_info *drm_info;
	struct drm_device *drm_dev;
	int ret;

	if (drm_firmware_drivers_only())
		return -ENODEV;

	DRM_INFO("Creating %s\n", xen_drm_driver.desc);

	drm_info = kzalloc(sizeof(*drm_info), GFP_KERNEL);
	if (!drm_info) {
		ret = -ENOMEM;
		goto fail;
	}

	drm_info->front_info = front_info;
	front_info->drm_info = drm_info;

	drm_dev = drm_dev_alloc(&xen_drm_driver, dev);
	if (IS_ERR(drm_dev)) {
		ret = PTR_ERR(drm_dev);
		goto fail_dev;
	}

	drm_info->drm_dev = drm_dev;

	drm_dev->dev_private = drm_info;

	ret = xen_drm_front_kms_init(drm_info);
	if (ret) {
		DRM_ERROR("Failed to initialize DRM/KMS, ret %d\n", ret);
		goto fail_modeset;
	}

	ret = drm_dev_register(drm_dev, 0);
	if (ret)
		goto fail_register;

	DRM_INFO("Initialized %s %d.%d.%d %s on minor %d\n",
		 xen_drm_driver.name, xen_drm_driver.major,
		 xen_drm_driver.minor, xen_drm_driver.patchlevel,
		 xen_drm_driver.date, drm_dev->primary->index);

	return 0;

fail_register:
	drm_dev_unregister(drm_dev);
fail_modeset:
	drm_kms_helper_poll_fini(drm_dev);
	drm_mode_config_cleanup(drm_dev);
	drm_dev_put(drm_dev);
fail_dev:
	kfree(drm_info);
	front_info->drm_info = NULL;
fail:
	return ret;
}

static void xen_drm_drv_fini(struct xen_drm_front_info *front_info)
{
	struct xen_drm_front_drm_info *drm_info = front_info->drm_info;
	struct drm_device *dev;

	if (!drm_info)
		return;

	dev = drm_info->drm_dev;
	if (!dev)
		return;

	/* Nothing to do if device is already unplugged */
	if (drm_dev_is_unplugged(dev))
		return;

	drm_kms_helper_poll_fini(dev);
	drm_dev_unplug(dev);
	drm_dev_put(dev);

	front_info->drm_info = NULL;

	xen_drm_front_evtchnl_free_all(front_info);
	dbuf_free_all(&front_info->dbuf_list);

	/*
	 * If we are not using backend allocated buffers, then tell the
	 * backend we are ready to (re)initialize. Otherwise, wait for
	 * drm_driver.release.
	 */
	if (!front_info->cfg.be_alloc)
		xenbus_switch_state(front_info->xb_dev,
				    XenbusStateInitialising);
}

static int displback_initwait(struct xen_drm_front_info *front_info)
{
	struct xen_drm_front_cfg *cfg = &front_info->cfg;
	int ret;

	cfg->front_info = front_info;
	ret = xen_drm_front_cfg_card(front_info, cfg);
	if (ret < 0)
		return ret;

	DRM_INFO("Have %d connector(s)\n", cfg->num_connectors);
	/* Create event channels for all connectors and publish */
	ret = xen_drm_front_evtchnl_create_all(front_info);
	if (ret < 0)
		return ret;

	return xen_drm_front_evtchnl_publish_all(front_info);
}

static int displback_connect(struct xen_drm_front_info *front_info)
{
	xen_drm_front_evtchnl_set_state(front_info, EVTCHNL_STATE_CONNECTED);
	return xen_drm_drv_init(front_info);
}

static void displback_disconnect(struct xen_drm_front_info *front_info)
{
	if (!front_info->drm_info)
		return;

	/* Tell the backend to wait until we release the DRM driver. */
	xenbus_switch_state(front_info->xb_dev, XenbusStateReconfiguring);

	xen_drm_drv_fini(front_info);
}

static void displback_changed(struct xenbus_device *xb_dev,
			      enum xenbus_state backend_state)
{
	struct xen_drm_front_info *front_info = dev_get_drvdata(&xb_dev->dev);
	int ret;

	DRM_DEBUG("Backend state is %s, front is %s\n",
		  xenbus_strstate(backend_state),
		  xenbus_strstate(xb_dev->state));

	switch (backend_state) {
	case XenbusStateReconfiguring:
	case XenbusStateReconfigured:
	case XenbusStateInitialised:
		break;

	case XenbusStateInitialising:
		if (xb_dev->state == XenbusStateReconfiguring)
			break;

		/* recovering after backend unexpected closure */
		displback_disconnect(front_info);
		break;

	case XenbusStateInitWait:
		if (xb_dev->state == XenbusStateReconfiguring)
			break;

		/* recovering after backend unexpected closure */
		displback_disconnect(front_info);
		if (xb_dev->state != XenbusStateInitialising)
			break;

		ret = displback_initwait(front_info);
		if (ret < 0)
			xenbus_dev_fatal(xb_dev, ret, "initializing frontend");
		else
			xenbus_switch_state(xb_dev, XenbusStateInitialised);
		break;

	case XenbusStateConnected:
		if (xb_dev->state != XenbusStateInitialised)
			break;

		ret = displback_connect(front_info);
		if (ret < 0) {
			displback_disconnect(front_info);
			xenbus_dev_fatal(xb_dev, ret, "connecting backend");
		} else {
			xenbus_switch_state(xb_dev, XenbusStateConnected);
		}
		break;

	case XenbusStateClosing:
		/*
		 * in this state backend starts freeing resources,
		 * so let it go into closed state, so we can also
		 * remove ours
		 */
		break;

	case XenbusStateUnknown:
	case XenbusStateClosed:
		if (xb_dev->state == XenbusStateClosed)
			break;

		displback_disconnect(front_info);
		break;
	}
}

static int xen_drv_probe(struct xenbus_device *xb_dev,
			 const struct xenbus_device_id *id)
{
	struct xen_drm_front_info *front_info;
	struct device *dev = &xb_dev->dev;
	int ret;

	ret = dma_coerce_mask_and_coherent(dev, DMA_BIT_MASK(64));
	if (ret < 0) {
		DRM_ERROR("Cannot setup DMA mask, ret %d", ret);
		return ret;
	}

	front_info = devm_kzalloc(&xb_dev->dev,
				  sizeof(*front_info), GFP_KERNEL);
	if (!front_info)
		return -ENOMEM;

	front_info->xb_dev = xb_dev;
	spin_lock_init(&front_info->io_lock);
	INIT_LIST_HEAD(&front_info->dbuf_list);
	dev_set_drvdata(&xb_dev->dev, front_info);

	return xenbus_switch_state(xb_dev, XenbusStateInitialising);
}

static int xen_drv_remove(struct xenbus_device *dev)
{
	struct xen_drm_front_info *front_info = dev_get_drvdata(&dev->dev);
	int to = 100;

	xenbus_switch_state(dev, XenbusStateClosing);

	/*
	 * On driver removal it is disconnected from XenBus,
	 * so no backend state change events come via .otherend_changed
	 * callback. This prevents us from exiting gracefully, e.g.
	 * signaling the backend to free event channels, waiting for its
	 * state to change to XenbusStateClosed and cleaning at our end.
	 * Normally when front driver removed backend will finally go into
	 * XenbusStateInitWait state.
	 *
	 * Workaround: read backend's state manually and wait with time-out.
	 */
	while ((xenbus_read_unsigned(front_info->xb_dev->otherend, "state",
				     XenbusStateUnknown) != XenbusStateInitWait) &&
				     --to)
		msleep(10);

	if (!to) {
		unsigned int state;

		state = xenbus_read_unsigned(front_info->xb_dev->otherend,
					     "state", XenbusStateUnknown);
		DRM_ERROR("Backend state is %s while removing driver\n",
			  xenbus_strstate(state));
	}

	xen_drm_drv_fini(front_info);
	xenbus_frontend_closed(dev);
	return 0;
}

static const struct xenbus_device_id xen_driver_ids[] = {
	{ XENDISPL_DRIVER_NAME },
	{ "" }
};

static struct xenbus_driver xen_driver = {
	.ids = xen_driver_ids,
	.probe = xen_drv_probe,
	.remove = xen_drv_remove,
	.otherend_changed = displback_changed,
	.not_essential = true,
};

static int __init xen_drv_init(void)
{
	/* At the moment we only support case with XEN_PAGE_SIZE == PAGE_SIZE */
	if (XEN_PAGE_SIZE != PAGE_SIZE) {
		DRM_ERROR(XENDISPL_DRIVER_NAME ": different kernel and Xen page sizes are not supported: XEN_PAGE_SIZE (%lu) != PAGE_SIZE (%lu)\n",
			  XEN_PAGE_SIZE, PAGE_SIZE);
		return -ENODEV;
	}

	if (!xen_domain())
		return -ENODEV;

	if (!xen_has_pv_devices())
		return -ENODEV;

	DRM_INFO("Registering XEN PV " XENDISPL_DRIVER_NAME "\n");
	return xenbus_register_frontend(&xen_driver);
}

static void __exit xen_drv_fini(void)
{
	DRM_INFO("Unregistering XEN PV " XENDISPL_DRIVER_NAME "\n");
	xenbus_unregister_driver(&xen_driver);
}

module_init(xen_drv_init);
module_exit(xen_drv_fini);

MODULE_DESCRIPTION("Xen para-virtualized display device frontend");
MODULE_LICENSE("GPL");
MODULE_ALIAS("xen:" XENDISPL_DRIVER_NAME);