summaryrefslogtreecommitdiff
path: root/drivers/gpu/drm/drm_vblank.c
blob: 2d5ce690d214b4835c395603ec3267e4e019eddb (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
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
/*
 * drm_irq.c IRQ and vblank support
 *
 * \author Rickard E. (Rik) Faith <faith@valinux.com>
 * \author Gareth Hughes <gareth@valinux.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

#include <linux/export.h>
#include <linux/moduleparam.h>

#include <drm/drm_crtc.h>
#include <drm/drm_drv.h>
#include <drm/drm_framebuffer.h>
#include <drm/drm_managed.h>
#include <drm/drm_modeset_helper_vtables.h>
#include <drm/drm_print.h>
#include <drm/drm_vblank.h>

#include "drm_internal.h"
#include "drm_trace.h"

/**
 * DOC: vblank handling
 *
 * From the computer's perspective, every time the monitor displays
 * a new frame the scanout engine has "scanned out" the display image
 * from top to bottom, one row of pixels at a time. The current row
 * of pixels is referred to as the current scanline.
 *
 * In addition to the display's visible area, there's usually a couple of
 * extra scanlines which aren't actually displayed on the screen.
 * These extra scanlines don't contain image data and are occasionally used
 * for features like audio and infoframes. The region made up of these
 * scanlines is referred to as the vertical blanking region, or vblank for
 * short.
 *
 * For historical reference, the vertical blanking period was designed to
 * give the electron gun (on CRTs) enough time to move back to the top of
 * the screen to start scanning out the next frame. Similar for horizontal
 * blanking periods. They were designed to give the electron gun enough
 * time to move back to the other side of the screen to start scanning the
 * next scanline.
 *
 * ::
 *
 *
 *    physical →   ⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽
 *    top of      |                                        |
 *    display     |                                        |
 *                |               New frame                |
 *                |                                        |
 *                |↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓|
 *                |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| ← Scanline,
 *                |↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓|   updates the
 *                |                                        |   frame as it
 *                |                                        |   travels down
 *                |                                        |   ("sacn out")
 *                |               Old frame                |
 *                |                                        |
 *                |                                        |
 *                |                                        |
 *                |                                        |   physical
 *                |                                        |   bottom of
 *    vertical    |⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽| ← display
 *    blanking    ┆xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx┆
 *    region   →  ┆xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx┆
 *                ┆xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx┆
 *    start of →   ⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽
 *    new frame
 *
 * "Physical top of display" is the reference point for the high-precision/
 * corrected timestamp.
 *
 * On a lot of display hardware, programming needs to take effect during the
 * vertical blanking period so that settings like gamma, the image buffer
 * buffer to be scanned out, etc. can safely be changed without showing
 * any visual artifacts on the screen. In some unforgiving hardware, some of
 * this programming has to both start and end in the same vblank. To help
 * with the timing of the hardware programming, an interrupt is usually
 * available to notify the driver when it can start the updating of registers.
 * The interrupt is in this context named the vblank interrupt.
 *
 * The vblank interrupt may be fired at different points depending on the
 * hardware. Some hardware implementations will fire the interrupt when the
 * new frame start, other implementations will fire the interrupt at different
 * points in time.
 *
 * Vertical blanking plays a major role in graphics rendering. To achieve
 * tear-free display, users must synchronize page flips and/or rendering to
 * vertical blanking. The DRM API offers ioctls to perform page flips
 * synchronized to vertical blanking and wait for vertical blanking.
 *
 * The DRM core handles most of the vertical blanking management logic, which
 * involves filtering out spurious interrupts, keeping race-free blanking
 * counters, coping with counter wrap-around and resets and keeping use counts.
 * It relies on the driver to generate vertical blanking interrupts and
 * optionally provide a hardware vertical blanking counter.
 *
 * Drivers must initialize the vertical blanking handling core with a call to
 * drm_vblank_init(). Minimally, a driver needs to implement
 * &drm_crtc_funcs.enable_vblank and &drm_crtc_funcs.disable_vblank plus call
 * drm_crtc_handle_vblank() in its vblank interrupt handler for working vblank
 * support.
 *
 * Vertical blanking interrupts can be enabled by the DRM core or by drivers
 * themselves (for instance to handle page flipping operations).  The DRM core
 * maintains a vertical blanking use count to ensure that the interrupts are not
 * disabled while a user still needs them. To increment the use count, drivers
 * call drm_crtc_vblank_get() and release the vblank reference again with
 * drm_crtc_vblank_put(). In between these two calls vblank interrupts are
 * guaranteed to be enabled.
 *
 * On many hardware disabling the vblank interrupt cannot be done in a race-free
 * manner, see &drm_driver.vblank_disable_immediate and
 * &drm_driver.max_vblank_count. In that case the vblank core only disables the
 * vblanks after a timer has expired, which can be configured through the
 * ``vblankoffdelay`` module parameter.
 *
 * Drivers for hardware without support for vertical-blanking interrupts
 * must not call drm_vblank_init(). For such drivers, atomic helpers will
 * automatically generate fake vblank events as part of the display update.
 * This functionality also can be controlled by the driver by enabling and
 * disabling struct drm_crtc_state.no_vblank.
 */

/* Retry timestamp calculation up to 3 times to satisfy
 * drm_timestamp_precision before giving up.
 */
#define DRM_TIMESTAMP_MAXRETRIES 3

/* Threshold in nanoseconds for detection of redundant
 * vblank irq in drm_handle_vblank(). 1 msec should be ok.
 */
#define DRM_REDUNDANT_VBLIRQ_THRESH_NS 1000000

static bool
drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe,
			  ktime_t *tvblank, bool in_vblank_irq);

static unsigned int drm_timestamp_precision = 20;  /* Default to 20 usecs. */

static int drm_vblank_offdelay = 5000;    /* Default to 5000 msecs. */

module_param_named(vblankoffdelay, drm_vblank_offdelay, int, 0600);
module_param_named(timestamp_precision_usec, drm_timestamp_precision, int, 0600);
MODULE_PARM_DESC(vblankoffdelay, "Delay until vblank irq auto-disable [msecs] (0: never disable, <0: disable immediately)");
MODULE_PARM_DESC(timestamp_precision_usec, "Max. error on timestamps [usecs]");

static void store_vblank(struct drm_device *dev, unsigned int pipe,
			 u32 vblank_count_inc,
			 ktime_t t_vblank, u32 last)
{
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];

	assert_spin_locked(&dev->vblank_time_lock);

	vblank->last = last;

	write_seqlock(&vblank->seqlock);
	vblank->time = t_vblank;
	atomic64_add(vblank_count_inc, &vblank->count);
	write_sequnlock(&vblank->seqlock);
}

static u32 drm_max_vblank_count(struct drm_device *dev, unsigned int pipe)
{
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];

	return vblank->max_vblank_count ?: dev->max_vblank_count;
}

/*
 * "No hw counter" fallback implementation of .get_vblank_counter() hook,
 * if there is no useable hardware frame counter available.
 */
static u32 drm_vblank_no_hw_counter(struct drm_device *dev, unsigned int pipe)
{
	WARN_ON_ONCE(drm_max_vblank_count(dev, pipe) != 0);
	return 0;
}

static u32 __get_vblank_counter(struct drm_device *dev, unsigned int pipe)
{
	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
		struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);

		if (WARN_ON(!crtc))
			return 0;

		if (crtc->funcs->get_vblank_counter)
			return crtc->funcs->get_vblank_counter(crtc);
	} else if (dev->driver->get_vblank_counter) {
		return dev->driver->get_vblank_counter(dev, pipe);
	}

	return drm_vblank_no_hw_counter(dev, pipe);
}

/*
 * Reset the stored timestamp for the current vblank count to correspond
 * to the last vblank occurred.
 *
 * Only to be called from drm_crtc_vblank_on().
 *
 * Note: caller must hold &drm_device.vbl_lock since this reads & writes
 * device vblank fields.
 */
static void drm_reset_vblank_timestamp(struct drm_device *dev, unsigned int pipe)
{
	u32 cur_vblank;
	bool rc;
	ktime_t t_vblank;
	int count = DRM_TIMESTAMP_MAXRETRIES;

	spin_lock(&dev->vblank_time_lock);

	/*
	 * sample the current counter to avoid random jumps
	 * when drm_vblank_enable() applies the diff
	 */
	do {
		cur_vblank = __get_vblank_counter(dev, pipe);
		rc = drm_get_last_vbltimestamp(dev, pipe, &t_vblank, false);
	} while (cur_vblank != __get_vblank_counter(dev, pipe) && --count > 0);

	/*
	 * Only reinitialize corresponding vblank timestamp if high-precision query
	 * available and didn't fail. Otherwise reinitialize delayed at next vblank
	 * interrupt and assign 0 for now, to mark the vblanktimestamp as invalid.
	 */
	if (!rc)
		t_vblank = 0;

	/*
	 * +1 to make sure user will never see the same
	 * vblank counter value before and after a modeset
	 */
	store_vblank(dev, pipe, 1, t_vblank, cur_vblank);

	spin_unlock(&dev->vblank_time_lock);
}

/*
 * Call back into the driver to update the appropriate vblank counter
 * (specified by @pipe).  Deal with wraparound, if it occurred, and
 * update the last read value so we can deal with wraparound on the next
 * call if necessary.
 *
 * Only necessary when going from off->on, to account for frames we
 * didn't get an interrupt for.
 *
 * Note: caller must hold &drm_device.vbl_lock since this reads & writes
 * device vblank fields.
 */
static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe,
				    bool in_vblank_irq)
{
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
	u32 cur_vblank, diff;
	bool rc;
	ktime_t t_vblank;
	int count = DRM_TIMESTAMP_MAXRETRIES;
	int framedur_ns = vblank->framedur_ns;
	u32 max_vblank_count = drm_max_vblank_count(dev, pipe);

	/*
	 * Interrupts were disabled prior to this call, so deal with counter
	 * wrap if needed.
	 * NOTE!  It's possible we lost a full dev->max_vblank_count + 1 events
	 * here if the register is small or we had vblank interrupts off for
	 * a long time.
	 *
	 * We repeat the hardware vblank counter & timestamp query until
	 * we get consistent results. This to prevent races between gpu
	 * updating its hardware counter while we are retrieving the
	 * corresponding vblank timestamp.
	 */
	do {
		cur_vblank = __get_vblank_counter(dev, pipe);
		rc = drm_get_last_vbltimestamp(dev, pipe, &t_vblank, in_vblank_irq);
	} while (cur_vblank != __get_vblank_counter(dev, pipe) && --count > 0);

	if (max_vblank_count) {
		/* trust the hw counter when it's around */
		diff = (cur_vblank - vblank->last) & max_vblank_count;
	} else if (rc && framedur_ns) {
		u64 diff_ns = ktime_to_ns(ktime_sub(t_vblank, vblank->time));

		/*
		 * Figure out how many vblanks we've missed based
		 * on the difference in the timestamps and the
		 * frame/field duration.
		 */

		DRM_DEBUG_VBL("crtc %u: Calculating number of vblanks."
			      " diff_ns = %lld, framedur_ns = %d)\n",
			      pipe, (long long) diff_ns, framedur_ns);

		diff = DIV_ROUND_CLOSEST_ULL(diff_ns, framedur_ns);

		if (diff == 0 && in_vblank_irq)
			DRM_DEBUG_VBL("crtc %u: Redundant vblirq ignored\n",
				      pipe);
	} else {
		/* some kind of default for drivers w/o accurate vbl timestamping */
		diff = in_vblank_irq ? 1 : 0;
	}

	/*
	 * Within a drm_vblank_pre_modeset - drm_vblank_post_modeset
	 * interval? If so then vblank irqs keep running and it will likely
	 * happen that the hardware vblank counter is not trustworthy as it
	 * might reset at some point in that interval and vblank timestamps
	 * are not trustworthy either in that interval. Iow. this can result
	 * in a bogus diff >> 1 which must be avoided as it would cause
	 * random large forward jumps of the software vblank counter.
	 */
	if (diff > 1 && (vblank->inmodeset & 0x2)) {
		DRM_DEBUG_VBL("clamping vblank bump to 1 on crtc %u: diffr=%u"
			      " due to pre-modeset.\n", pipe, diff);
		diff = 1;
	}

	DRM_DEBUG_VBL("updating vblank count on crtc %u:"
		      " current=%llu, diff=%u, hw=%u hw_last=%u\n",
		      pipe, (unsigned long long)atomic64_read(&vblank->count),
		      diff, cur_vblank, vblank->last);

	if (diff == 0) {
		WARN_ON_ONCE(cur_vblank != vblank->last);
		return;
	}

	/*
	 * Only reinitialize corresponding vblank timestamp if high-precision query
	 * available and didn't fail, or we were called from the vblank interrupt.
	 * Otherwise reinitialize delayed at next vblank interrupt and assign 0
	 * for now, to mark the vblanktimestamp as invalid.
	 */
	if (!rc && !in_vblank_irq)
		t_vblank = 0;

	store_vblank(dev, pipe, diff, t_vblank, cur_vblank);
}

static u64 drm_vblank_count(struct drm_device *dev, unsigned int pipe)
{
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
	u64 count;

	if (WARN_ON(pipe >= dev->num_crtcs))
		return 0;

	count = atomic64_read(&vblank->count);

	/*
	 * This read barrier corresponds to the implicit write barrier of the
	 * write seqlock in store_vblank(). Note that this is the only place
	 * where we need an explicit barrier, since all other access goes
	 * through drm_vblank_count_and_time(), which already has the required
	 * read barrier curtesy of the read seqlock.
	 */
	smp_rmb();

	return count;
}

/**
 * drm_crtc_accurate_vblank_count - retrieve the master vblank counter
 * @crtc: which counter to retrieve
 *
 * This function is similar to drm_crtc_vblank_count() but this function
 * interpolates to handle a race with vblank interrupts using the high precision
 * timestamping support.
 *
 * This is mostly useful for hardware that can obtain the scanout position, but
 * doesn't have a hardware frame counter.
 */
u64 drm_crtc_accurate_vblank_count(struct drm_crtc *crtc)
{
	struct drm_device *dev = crtc->dev;
	unsigned int pipe = drm_crtc_index(crtc);
	u64 vblank;
	unsigned long flags;

	WARN_ONCE(drm_debug_enabled(DRM_UT_VBL) &&
		  !crtc->funcs->get_vblank_timestamp,
		  "This function requires support for accurate vblank timestamps.");

	spin_lock_irqsave(&dev->vblank_time_lock, flags);

	drm_update_vblank_count(dev, pipe, false);
	vblank = drm_vblank_count(dev, pipe);

	spin_unlock_irqrestore(&dev->vblank_time_lock, flags);

	return vblank;
}
EXPORT_SYMBOL(drm_crtc_accurate_vblank_count);

static void __disable_vblank(struct drm_device *dev, unsigned int pipe)
{
	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
		struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);

		if (WARN_ON(!crtc))
			return;

		if (crtc->funcs->disable_vblank)
			crtc->funcs->disable_vblank(crtc);
	} else {
		dev->driver->disable_vblank(dev, pipe);
	}
}

/*
 * Disable vblank irq's on crtc, make sure that last vblank count
 * of hardware and corresponding consistent software vblank counter
 * are preserved, even if there are any spurious vblank irq's after
 * disable.
 */
void drm_vblank_disable_and_save(struct drm_device *dev, unsigned int pipe)
{
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
	unsigned long irqflags;

	assert_spin_locked(&dev->vbl_lock);

	/* Prevent vblank irq processing while disabling vblank irqs,
	 * so no updates of timestamps or count can happen after we've
	 * disabled. Needed to prevent races in case of delayed irq's.
	 */
	spin_lock_irqsave(&dev->vblank_time_lock, irqflags);

	/*
	 * Update vblank count and disable vblank interrupts only if the
	 * interrupts were enabled. This avoids calling the ->disable_vblank()
	 * operation in atomic context with the hardware potentially runtime
	 * suspended.
	 */
	if (!vblank->enabled)
		goto out;

	/*
	 * Update the count and timestamp to maintain the
	 * appearance that the counter has been ticking all along until
	 * this time. This makes the count account for the entire time
	 * between drm_crtc_vblank_on() and drm_crtc_vblank_off().
	 */
	drm_update_vblank_count(dev, pipe, false);
	__disable_vblank(dev, pipe);
	vblank->enabled = false;

out:
	spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags);
}

static void vblank_disable_fn(struct timer_list *t)
{
	struct drm_vblank_crtc *vblank = from_timer(vblank, t, disable_timer);
	struct drm_device *dev = vblank->dev;
	unsigned int pipe = vblank->pipe;
	unsigned long irqflags;

	spin_lock_irqsave(&dev->vbl_lock, irqflags);
	if (atomic_read(&vblank->refcount) == 0 && vblank->enabled) {
		DRM_DEBUG("disabling vblank on crtc %u\n", pipe);
		drm_vblank_disable_and_save(dev, pipe);
	}
	spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
}

static void drm_vblank_init_release(struct drm_device *dev, void *ptr)
{
	unsigned int pipe;

	for (pipe = 0; pipe < dev->num_crtcs; pipe++) {
		struct drm_vblank_crtc *vblank = &dev->vblank[pipe];

		WARN_ON(READ_ONCE(vblank->enabled) &&
			drm_core_check_feature(dev, DRIVER_MODESET));

		del_timer_sync(&vblank->disable_timer);
	}
}

/**
 * drm_vblank_init - initialize vblank support
 * @dev: DRM device
 * @num_crtcs: number of CRTCs supported by @dev
 *
 * This function initializes vblank support for @num_crtcs display pipelines.
 * Cleanup is handled automatically through a cleanup function added with
 * drmm_add_action().
 *
 * Returns:
 * Zero on success or a negative error code on failure.
 */
int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs)
{
	int ret;
	unsigned int i;

	spin_lock_init(&dev->vbl_lock);
	spin_lock_init(&dev->vblank_time_lock);

	dev->vblank = drmm_kcalloc(dev, num_crtcs, sizeof(*dev->vblank), GFP_KERNEL);
	if (!dev->vblank)
		return -ENOMEM;

	dev->num_crtcs = num_crtcs;

	ret = drmm_add_action(dev, drm_vblank_init_release, NULL);
	if (ret)
		return ret;

	for (i = 0; i < num_crtcs; i++) {
		struct drm_vblank_crtc *vblank = &dev->vblank[i];

		vblank->dev = dev;
		vblank->pipe = i;
		init_waitqueue_head(&vblank->queue);
		timer_setup(&vblank->disable_timer, vblank_disable_fn, 0);
		seqlock_init(&vblank->seqlock);
	}

	DRM_INFO("Supports vblank timestamp caching Rev 2 (21.10.2013).\n");

	return 0;
}
EXPORT_SYMBOL(drm_vblank_init);

/**
 * drm_dev_has_vblank - test if vblanking has been initialized for
 *                      a device
 * @dev: the device
 *
 * Drivers may call this function to test if vblank support is
 * initialized for a device. For most hardware this means that vblanking
 * can also be enabled.
 *
 * Atomic helpers use this function to initialize
 * &drm_crtc_state.no_vblank. See also drm_atomic_helper_check_modeset().
 *
 * Returns:
 * True if vblanking has been initialized for the given device, false
 * otherwise.
 */
bool drm_dev_has_vblank(const struct drm_device *dev)
{
	return dev->num_crtcs != 0;
}
EXPORT_SYMBOL(drm_dev_has_vblank);

/**
 * drm_crtc_vblank_waitqueue - get vblank waitqueue for the CRTC
 * @crtc: which CRTC's vblank waitqueue to retrieve
 *
 * This function returns a pointer to the vblank waitqueue for the CRTC.
 * Drivers can use this to implement vblank waits using wait_event() and related
 * functions.
 */
wait_queue_head_t *drm_crtc_vblank_waitqueue(struct drm_crtc *crtc)
{
	return &crtc->dev->vblank[drm_crtc_index(crtc)].queue;
}
EXPORT_SYMBOL(drm_crtc_vblank_waitqueue);


/**
 * drm_calc_timestamping_constants - calculate vblank timestamp constants
 * @crtc: drm_crtc whose timestamp constants should be updated.
 * @mode: display mode containing the scanout timings
 *
 * Calculate and store various constants which are later needed by vblank and
 * swap-completion timestamping, e.g, by
 * drm_crtc_vblank_helper_get_vblank_timestamp(). They are derived from
 * CRTC's true scanout timing, so they take things like panel scaling or
 * other adjustments into account.
 */
void drm_calc_timestamping_constants(struct drm_crtc *crtc,
				     const struct drm_display_mode *mode)
{
	struct drm_device *dev = crtc->dev;
	unsigned int pipe = drm_crtc_index(crtc);
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
	int linedur_ns = 0, framedur_ns = 0;
	int dotclock = mode->crtc_clock;

	if (!dev->num_crtcs)
		return;

	if (WARN_ON(pipe >= dev->num_crtcs))
		return;

	/* Valid dotclock? */
	if (dotclock > 0) {
		int frame_size = mode->crtc_htotal * mode->crtc_vtotal;

		/*
		 * Convert scanline length in pixels and video
		 * dot clock to line duration and frame duration
		 * in nanoseconds:
		 */
		linedur_ns  = div_u64((u64) mode->crtc_htotal * 1000000, dotclock);
		framedur_ns = div_u64((u64) frame_size * 1000000, dotclock);

		/*
		 * Fields of interlaced scanout modes are only half a frame duration.
		 */
		if (mode->flags & DRM_MODE_FLAG_INTERLACE)
			framedur_ns /= 2;
	} else
		DRM_ERROR("crtc %u: Can't calculate constants, dotclock = 0!\n",
			  crtc->base.id);

	vblank->linedur_ns  = linedur_ns;
	vblank->framedur_ns = framedur_ns;
	vblank->hwmode = *mode;

	DRM_DEBUG("crtc %u: hwmode: htotal %d, vtotal %d, vdisplay %d\n",
		  crtc->base.id, mode->crtc_htotal,
		  mode->crtc_vtotal, mode->crtc_vdisplay);
	DRM_DEBUG("crtc %u: clock %d kHz framedur %d linedur %d\n",
		  crtc->base.id, dotclock, framedur_ns, linedur_ns);
}
EXPORT_SYMBOL(drm_calc_timestamping_constants);

/**
 * drm_crtc_vblank_helper_get_vblank_timestamp_internal - precise vblank
 *                                                        timestamp helper
 * @crtc: CRTC whose vblank timestamp to retrieve
 * @max_error: Desired maximum allowable error in timestamps (nanosecs)
 *             On return contains true maximum error of timestamp
 * @vblank_time: Pointer to time which should receive the timestamp
 * @in_vblank_irq:
 *     True when called from drm_crtc_handle_vblank().  Some drivers
 *     need to apply some workarounds for gpu-specific vblank irq quirks
 *     if flag is set.
 * @get_scanout_position:
 *     Callback function to retrieve the scanout position. See
 *     @struct drm_crtc_helper_funcs.get_scanout_position.
 *
 * Implements calculation of exact vblank timestamps from given drm_display_mode
 * timings and current video scanout position of a CRTC.
 *
 * The current implementation only handles standard video modes. For double scan
 * and interlaced modes the driver is supposed to adjust the hardware mode
 * (taken from &drm_crtc_state.adjusted mode for atomic modeset drivers) to
 * match the scanout position reported.
 *
 * Note that atomic drivers must call drm_calc_timestamping_constants() before
 * enabling a CRTC. The atomic helpers already take care of that in
 * drm_atomic_helper_update_legacy_modeset_state().
 *
 * Returns:
 *
 * Returns true on success, and false on failure, i.e. when no accurate
 * timestamp could be acquired.
 */
bool
drm_crtc_vblank_helper_get_vblank_timestamp_internal(
	struct drm_crtc *crtc, int *max_error, ktime_t *vblank_time,
	bool in_vblank_irq,
	drm_vblank_get_scanout_position_func get_scanout_position)
{
	struct drm_device *dev = crtc->dev;
	unsigned int pipe = crtc->index;
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
	struct timespec64 ts_etime, ts_vblank_time;
	ktime_t stime, etime;
	bool vbl_status;
	const struct drm_display_mode *mode;
	int vpos, hpos, i;
	int delta_ns, duration_ns;

	if (pipe >= dev->num_crtcs) {
		DRM_ERROR("Invalid crtc %u\n", pipe);
		return false;
	}

	/* Scanout position query not supported? Should not happen. */
	if (!get_scanout_position) {
		DRM_ERROR("Called from CRTC w/o get_scanout_position()!?\n");
		return false;
	}

	if (drm_drv_uses_atomic_modeset(dev))
		mode = &vblank->hwmode;
	else
		mode = &crtc->hwmode;

	/* If mode timing undefined, just return as no-op:
	 * Happens during initial modesetting of a crtc.
	 */
	if (mode->crtc_clock == 0) {
		DRM_DEBUG("crtc %u: Noop due to uninitialized mode.\n", pipe);
		WARN_ON_ONCE(drm_drv_uses_atomic_modeset(dev));
		return false;
	}

	/* Get current scanout position with system timestamp.
	 * Repeat query up to DRM_TIMESTAMP_MAXRETRIES times
	 * if single query takes longer than max_error nanoseconds.
	 *
	 * This guarantees a tight bound on maximum error if
	 * code gets preempted or delayed for some reason.
	 */
	for (i = 0; i < DRM_TIMESTAMP_MAXRETRIES; i++) {
		/*
		 * Get vertical and horizontal scanout position vpos, hpos,
		 * and bounding timestamps stime, etime, pre/post query.
		 */
		vbl_status = get_scanout_position(crtc, in_vblank_irq,
						  &vpos, &hpos,
						  &stime, &etime,
						  mode);

		/* Return as no-op if scanout query unsupported or failed. */
		if (!vbl_status) {
			DRM_DEBUG("crtc %u : scanoutpos query failed.\n",
				  pipe);
			return false;
		}

		/* Compute uncertainty in timestamp of scanout position query. */
		duration_ns = ktime_to_ns(etime) - ktime_to_ns(stime);

		/* Accept result with <  max_error nsecs timing uncertainty. */
		if (duration_ns <= *max_error)
			break;
	}

	/* Noisy system timing? */
	if (i == DRM_TIMESTAMP_MAXRETRIES) {
		DRM_DEBUG("crtc %u: Noisy timestamp %d us > %d us [%d reps].\n",
			  pipe, duration_ns/1000, *max_error/1000, i);
	}

	/* Return upper bound of timestamp precision error. */
	*max_error = duration_ns;

	/* Convert scanout position into elapsed time at raw_time query
	 * since start of scanout at first display scanline. delta_ns
	 * can be negative if start of scanout hasn't happened yet.
	 */
	delta_ns = div_s64(1000000LL * (vpos * mode->crtc_htotal + hpos),
			   mode->crtc_clock);

	/* Subtract time delta from raw timestamp to get final
	 * vblank_time timestamp for end of vblank.
	 */
	*vblank_time = ktime_sub_ns(etime, delta_ns);

	if (!drm_debug_enabled(DRM_UT_VBL))
		return true;

	ts_etime = ktime_to_timespec64(etime);
	ts_vblank_time = ktime_to_timespec64(*vblank_time);

	DRM_DEBUG_VBL("crtc %u : v p(%d,%d)@ %lld.%06ld -> %lld.%06ld [e %d us, %d rep]\n",
		      pipe, hpos, vpos,
		      (u64)ts_etime.tv_sec, ts_etime.tv_nsec / 1000,
		      (u64)ts_vblank_time.tv_sec, ts_vblank_time.tv_nsec / 1000,
		      duration_ns / 1000, i);

	return true;
}
EXPORT_SYMBOL(drm_crtc_vblank_helper_get_vblank_timestamp_internal);

/**
 * drm_crtc_vblank_helper_get_vblank_timestamp - precise vblank timestamp
 *                                               helper
 * @crtc: CRTC whose vblank timestamp to retrieve
 * @max_error: Desired maximum allowable error in timestamps (nanosecs)
 *             On return contains true maximum error of timestamp
 * @vblank_time: Pointer to time which should receive the timestamp
 * @in_vblank_irq:
 *     True when called from drm_crtc_handle_vblank().  Some drivers
 *     need to apply some workarounds for gpu-specific vblank irq quirks
 *     if flag is set.
 *
 * Implements calculation of exact vblank timestamps from given drm_display_mode
 * timings and current video scanout position of a CRTC. This can be directly
 * used as the &drm_crtc_funcs.get_vblank_timestamp implementation of a kms
 * driver if &drm_crtc_helper_funcs.get_scanout_position is implemented.
 *
 * The current implementation only handles standard video modes. For double scan
 * and interlaced modes the driver is supposed to adjust the hardware mode
 * (taken from &drm_crtc_state.adjusted mode for atomic modeset drivers) to
 * match the scanout position reported.
 *
 * Note that atomic drivers must call drm_calc_timestamping_constants() before
 * enabling a CRTC. The atomic helpers already take care of that in
 * drm_atomic_helper_update_legacy_modeset_state().
 *
 * Returns:
 *
 * Returns true on success, and false on failure, i.e. when no accurate
 * timestamp could be acquired.
 */
bool drm_crtc_vblank_helper_get_vblank_timestamp(struct drm_crtc *crtc,
						 int *max_error,
						 ktime_t *vblank_time,
						 bool in_vblank_irq)
{
	return drm_crtc_vblank_helper_get_vblank_timestamp_internal(
		crtc, max_error, vblank_time, in_vblank_irq,
		crtc->helper_private->get_scanout_position);
}
EXPORT_SYMBOL(drm_crtc_vblank_helper_get_vblank_timestamp);

/**
 * drm_get_last_vbltimestamp - retrieve raw timestamp for the most recent
 *                             vblank interval
 * @dev: DRM device
 * @pipe: index of CRTC whose vblank timestamp to retrieve
 * @tvblank: Pointer to target time which should receive the timestamp
 * @in_vblank_irq:
 *     True when called from drm_crtc_handle_vblank().  Some drivers
 *     need to apply some workarounds for gpu-specific vblank irq quirks
 *     if flag is set.
 *
 * Fetches the system timestamp corresponding to the time of the most recent
 * vblank interval on specified CRTC. May call into kms-driver to
 * compute the timestamp with a high-precision GPU specific method.
 *
 * Returns zero if timestamp originates from uncorrected do_gettimeofday()
 * call, i.e., it isn't very precisely locked to the true vblank.
 *
 * Returns:
 * True if timestamp is considered to be very precise, false otherwise.
 */
static bool
drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe,
			  ktime_t *tvblank, bool in_vblank_irq)
{
	struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
	bool ret = false;

	/* Define requested maximum error on timestamps (nanoseconds). */
	int max_error = (int) drm_timestamp_precision * 1000;

	/* Query driver if possible and precision timestamping enabled. */
	if (crtc && crtc->funcs->get_vblank_timestamp && max_error > 0) {
		struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);

		ret = crtc->funcs->get_vblank_timestamp(crtc, &max_error,
							tvblank, in_vblank_irq);
	}

	/* GPU high precision timestamp query unsupported or failed.
	 * Return current monotonic/gettimeofday timestamp as best estimate.
	 */
	if (!ret)
		*tvblank = ktime_get();

	return ret;
}

/**
 * drm_crtc_vblank_count - retrieve "cooked" vblank counter value
 * @crtc: which counter to retrieve
 *
 * Fetches the "cooked" vblank count value that represents the number of
 * vblank events since the system was booted, including lost events due to
 * modesetting activity. Note that this timer isn't correct against a racing
 * vblank interrupt (since it only reports the software vblank counter), see
 * drm_crtc_accurate_vblank_count() for such use-cases.
 *
 * Note that for a given vblank counter value drm_crtc_handle_vblank()
 * and drm_crtc_vblank_count() or drm_crtc_vblank_count_and_time()
 * provide a barrier: Any writes done before calling
 * drm_crtc_handle_vblank() will be visible to callers of the later
 * functions, iff the vblank count is the same or a later one.
 *
 * See also &drm_vblank_crtc.count.
 *
 * Returns:
 * The software vblank counter.
 */
u64 drm_crtc_vblank_count(struct drm_crtc *crtc)
{
	return drm_vblank_count(crtc->dev, drm_crtc_index(crtc));
}
EXPORT_SYMBOL(drm_crtc_vblank_count);

/**
 * drm_vblank_count_and_time - retrieve "cooked" vblank counter value and the
 *     system timestamp corresponding to that vblank counter value.
 * @dev: DRM device
 * @pipe: index of CRTC whose counter to retrieve
 * @vblanktime: Pointer to ktime_t to receive the vblank timestamp.
 *
 * Fetches the "cooked" vblank count value that represents the number of
 * vblank events since the system was booted, including lost events due to
 * modesetting activity. Returns corresponding system timestamp of the time
 * of the vblank interval that corresponds to the current vblank counter value.
 *
 * This is the legacy version of drm_crtc_vblank_count_and_time().
 */
static u64 drm_vblank_count_and_time(struct drm_device *dev, unsigned int pipe,
				     ktime_t *vblanktime)
{
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
	u64 vblank_count;
	unsigned int seq;

	if (WARN_ON(pipe >= dev->num_crtcs)) {
		*vblanktime = 0;
		return 0;
	}

	do {
		seq = read_seqbegin(&vblank->seqlock);
		vblank_count = atomic64_read(&vblank->count);
		*vblanktime = vblank->time;
	} while (read_seqretry(&vblank->seqlock, seq));

	return vblank_count;
}

/**
 * drm_crtc_vblank_count_and_time - retrieve "cooked" vblank counter value
 *     and the system timestamp corresponding to that vblank counter value
 * @crtc: which counter to retrieve
 * @vblanktime: Pointer to time to receive the vblank timestamp.
 *
 * Fetches the "cooked" vblank count value that represents the number of
 * vblank events since the system was booted, including lost events due to
 * modesetting activity. Returns corresponding system timestamp of the time
 * of the vblank interval that corresponds to the current vblank counter value.
 *
 * Note that for a given vblank counter value drm_crtc_handle_vblank()
 * and drm_crtc_vblank_count() or drm_crtc_vblank_count_and_time()
 * provide a barrier: Any writes done before calling
 * drm_crtc_handle_vblank() will be visible to callers of the later
 * functions, iff the vblank count is the same or a later one.
 *
 * See also &drm_vblank_crtc.count.
 */
u64 drm_crtc_vblank_count_and_time(struct drm_crtc *crtc,
				   ktime_t *vblanktime)
{
	return drm_vblank_count_and_time(crtc->dev, drm_crtc_index(crtc),
					 vblanktime);
}
EXPORT_SYMBOL(drm_crtc_vblank_count_and_time);

static void send_vblank_event(struct drm_device *dev,
		struct drm_pending_vblank_event *e,
		u64 seq, ktime_t now)
{
	struct timespec64 tv;

	switch (e->event.base.type) {
	case DRM_EVENT_VBLANK:
	case DRM_EVENT_FLIP_COMPLETE:
		tv = ktime_to_timespec64(now);
		e->event.vbl.sequence = seq;
		/*
		 * e->event is a user space structure, with hardcoded unsigned
		 * 32-bit seconds/microseconds. This is safe as we always use
		 * monotonic timestamps since linux-4.15
		 */
		e->event.vbl.tv_sec = tv.tv_sec;
		e->event.vbl.tv_usec = tv.tv_nsec / 1000;
		break;
	case DRM_EVENT_CRTC_SEQUENCE:
		if (seq)
			e->event.seq.sequence = seq;
		e->event.seq.time_ns = ktime_to_ns(now);
		break;
	}
	trace_drm_vblank_event_delivered(e->base.file_priv, e->pipe, seq);
	drm_send_event_locked(dev, &e->base);
}

/**
 * drm_crtc_arm_vblank_event - arm vblank event after pageflip
 * @crtc: the source CRTC of the vblank event
 * @e: the event to send
 *
 * A lot of drivers need to generate vblank events for the very next vblank
 * interrupt. For example when the page flip interrupt happens when the page
 * flip gets armed, but not when it actually executes within the next vblank
 * period. This helper function implements exactly the required vblank arming
 * behaviour.
 *
 * NOTE: Drivers using this to send out the &drm_crtc_state.event as part of an
 * atomic commit must ensure that the next vblank happens at exactly the same
 * time as the atomic commit is committed to the hardware. This function itself
 * does **not** protect against the next vblank interrupt racing with either this
 * function call or the atomic commit operation. A possible sequence could be:
 *
 * 1. Driver commits new hardware state into vblank-synchronized registers.
 * 2. A vblank happens, committing the hardware state. Also the corresponding
 *    vblank interrupt is fired off and fully processed by the interrupt
 *    handler.
 * 3. The atomic commit operation proceeds to call drm_crtc_arm_vblank_event().
 * 4. The event is only send out for the next vblank, which is wrong.
 *
 * An equivalent race can happen when the driver calls
 * drm_crtc_arm_vblank_event() before writing out the new hardware state.
 *
 * The only way to make this work safely is to prevent the vblank from firing
 * (and the hardware from committing anything else) until the entire atomic
 * commit sequence has run to completion. If the hardware does not have such a
 * feature (e.g. using a "go" bit), then it is unsafe to use this functions.
 * Instead drivers need to manually send out the event from their interrupt
 * handler by calling drm_crtc_send_vblank_event() and make sure that there's no
 * possible race with the hardware committing the atomic update.
 *
 * Caller must hold a vblank reference for the event @e acquired by a
 * drm_crtc_vblank_get(), which will be dropped when the next vblank arrives.
 */
void drm_crtc_arm_vblank_event(struct drm_crtc *crtc,
			       struct drm_pending_vblank_event *e)
{
	struct drm_device *dev = crtc->dev;
	unsigned int pipe = drm_crtc_index(crtc);

	assert_spin_locked(&dev->event_lock);

	e->pipe = pipe;
	e->sequence = drm_crtc_accurate_vblank_count(crtc) + 1;
	list_add_tail(&e->base.link, &dev->vblank_event_list);
}
EXPORT_SYMBOL(drm_crtc_arm_vblank_event);

/**
 * drm_crtc_send_vblank_event - helper to send vblank event after pageflip
 * @crtc: the source CRTC of the vblank event
 * @e: the event to send
 *
 * Updates sequence # and timestamp on event for the most recently processed
 * vblank, and sends it to userspace.  Caller must hold event lock.
 *
 * See drm_crtc_arm_vblank_event() for a helper which can be used in certain
 * situation, especially to send out events for atomic commit operations.
 */
void drm_crtc_send_vblank_event(struct drm_crtc *crtc,
				struct drm_pending_vblank_event *e)
{
	struct drm_device *dev = crtc->dev;
	u64 seq;
	unsigned int pipe = drm_crtc_index(crtc);
	ktime_t now;

	if (dev->num_crtcs > 0) {
		seq = drm_vblank_count_and_time(dev, pipe, &now);
	} else {
		seq = 0;

		now = ktime_get();
	}
	e->pipe = pipe;
	send_vblank_event(dev, e, seq, now);
}
EXPORT_SYMBOL(drm_crtc_send_vblank_event);

static int __enable_vblank(struct drm_device *dev, unsigned int pipe)
{
	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
		struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);

		if (WARN_ON(!crtc))
			return 0;

		if (crtc->funcs->enable_vblank)
			return crtc->funcs->enable_vblank(crtc);
	} else if (dev->driver->enable_vblank) {
		return dev->driver->enable_vblank(dev, pipe);
	}

	return -EINVAL;
}

static int drm_vblank_enable(struct drm_device *dev, unsigned int pipe)
{
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
	int ret = 0;

	assert_spin_locked(&dev->vbl_lock);

	spin_lock(&dev->vblank_time_lock);

	if (!vblank->enabled) {
		/*
		 * Enable vblank irqs under vblank_time_lock protection.
		 * All vblank count & timestamp updates are held off
		 * until we are done reinitializing master counter and
		 * timestamps. Filtercode in drm_handle_vblank() will
		 * prevent double-accounting of same vblank interval.
		 */
		ret = __enable_vblank(dev, pipe);
		DRM_DEBUG("enabling vblank on crtc %u, ret: %d\n", pipe, ret);
		if (ret) {
			atomic_dec(&vblank->refcount);
		} else {
			drm_update_vblank_count(dev, pipe, 0);
			/* drm_update_vblank_count() includes a wmb so we just
			 * need to ensure that the compiler emits the write
			 * to mark the vblank as enabled after the call
			 * to drm_update_vblank_count().
			 */
			WRITE_ONCE(vblank->enabled, true);
		}
	}

	spin_unlock(&dev->vblank_time_lock);

	return ret;
}

static int drm_vblank_get(struct drm_device *dev, unsigned int pipe)
{
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
	unsigned long irqflags;
	int ret = 0;

	if (!dev->num_crtcs)
		return -EINVAL;

	if (WARN_ON(pipe >= dev->num_crtcs))
		return -EINVAL;

	spin_lock_irqsave(&dev->vbl_lock, irqflags);
	/* Going from 0->1 means we have to enable interrupts again */
	if (atomic_add_return(1, &vblank->refcount) == 1) {
		ret = drm_vblank_enable(dev, pipe);
	} else {
		if (!vblank->enabled) {
			atomic_dec(&vblank->refcount);
			ret = -EINVAL;
		}
	}
	spin_unlock_irqrestore(&dev->vbl_lock, irqflags);

	return ret;
}

/**
 * drm_crtc_vblank_get - get a reference count on vblank events
 * @crtc: which CRTC to own
 *
 * Acquire a reference count on vblank events to avoid having them disabled
 * while in use.
 *
 * Returns:
 * Zero on success or a negative error code on failure.
 */
int drm_crtc_vblank_get(struct drm_crtc *crtc)
{
	return drm_vblank_get(crtc->dev, drm_crtc_index(crtc));
}
EXPORT_SYMBOL(drm_crtc_vblank_get);

static void drm_vblank_put(struct drm_device *dev, unsigned int pipe)
{
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];

	if (WARN_ON(pipe >= dev->num_crtcs))
		return;

	if (WARN_ON(atomic_read(&vblank->refcount) == 0))
		return;

	/* Last user schedules interrupt disable */
	if (atomic_dec_and_test(&vblank->refcount)) {
		if (drm_vblank_offdelay == 0)
			return;
		else if (drm_vblank_offdelay < 0)
			vblank_disable_fn(&vblank->disable_timer);
		else if (!dev->vblank_disable_immediate)
			mod_timer(&vblank->disable_timer,
				  jiffies + ((drm_vblank_offdelay * HZ)/1000));
	}
}

/**
 * drm_crtc_vblank_put - give up ownership of vblank events
 * @crtc: which counter to give up
 *
 * Release ownership of a given vblank counter, turning off interrupts
 * if possible. Disable interrupts after drm_vblank_offdelay milliseconds.
 */
void drm_crtc_vblank_put(struct drm_crtc *crtc)
{
	drm_vblank_put(crtc->dev, drm_crtc_index(crtc));
}
EXPORT_SYMBOL(drm_crtc_vblank_put);

/**
 * drm_wait_one_vblank - wait for one vblank
 * @dev: DRM device
 * @pipe: CRTC index
 *
 * This waits for one vblank to pass on @pipe, using the irq driver interfaces.
 * It is a failure to call this when the vblank irq for @pipe is disabled, e.g.
 * due to lack of driver support or because the crtc is off.
 *
 * This is the legacy version of drm_crtc_wait_one_vblank().
 */
void drm_wait_one_vblank(struct drm_device *dev, unsigned int pipe)
{
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
	int ret;
	u64 last;

	if (WARN_ON(pipe >= dev->num_crtcs))
		return;

	ret = drm_vblank_get(dev, pipe);
	if (WARN(ret, "vblank not available on crtc %i, ret=%i\n", pipe, ret))
		return;

	last = drm_vblank_count(dev, pipe);

	ret = wait_event_timeout(vblank->queue,
				 last != drm_vblank_count(dev, pipe),
				 msecs_to_jiffies(100));

	WARN(ret == 0, "vblank wait timed out on crtc %i\n", pipe);

	drm_vblank_put(dev, pipe);
}
EXPORT_SYMBOL(drm_wait_one_vblank);

/**
 * drm_crtc_wait_one_vblank - wait for one vblank
 * @crtc: DRM crtc
 *
 * This waits for one vblank to pass on @crtc, using the irq driver interfaces.
 * It is a failure to call this when the vblank irq for @crtc is disabled, e.g.
 * due to lack of driver support or because the crtc is off.
 */
void drm_crtc_wait_one_vblank(struct drm_crtc *crtc)
{
	drm_wait_one_vblank(crtc->dev, drm_crtc_index(crtc));
}
EXPORT_SYMBOL(drm_crtc_wait_one_vblank);

/**
 * drm_crtc_vblank_off - disable vblank events on a CRTC
 * @crtc: CRTC in question
 *
 * Drivers can use this function to shut down the vblank interrupt handling when
 * disabling a crtc. This function ensures that the latest vblank frame count is
 * stored so that drm_vblank_on can restore it again.
 *
 * Drivers must use this function when the hardware vblank counter can get
 * reset, e.g. when suspending or disabling the @crtc in general.
 */
void drm_crtc_vblank_off(struct drm_crtc *crtc)
{
	struct drm_device *dev = crtc->dev;
	unsigned int pipe = drm_crtc_index(crtc);
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
	struct drm_pending_vblank_event *e, *t;

	ktime_t now;
	unsigned long irqflags;
	u64 seq;

	if (WARN_ON(pipe >= dev->num_crtcs))
		return;

	spin_lock_irqsave(&dev->event_lock, irqflags);

	spin_lock(&dev->vbl_lock);
	DRM_DEBUG_VBL("crtc %d, vblank enabled %d, inmodeset %d\n",
		      pipe, vblank->enabled, vblank->inmodeset);

	/* Avoid redundant vblank disables without previous
	 * drm_crtc_vblank_on(). */
	if (drm_core_check_feature(dev, DRIVER_ATOMIC) || !vblank->inmodeset)
		drm_vblank_disable_and_save(dev, pipe);

	wake_up(&vblank->queue);

	/*
	 * Prevent subsequent drm_vblank_get() from re-enabling
	 * the vblank interrupt by bumping the refcount.
	 */
	if (!vblank->inmodeset) {
		atomic_inc(&vblank->refcount);
		vblank->inmodeset = 1;
	}
	spin_unlock(&dev->vbl_lock);

	/* Send any queued vblank events, lest the natives grow disquiet */
	seq = drm_vblank_count_and_time(dev, pipe, &now);

	list_for_each_entry_safe(e, t, &dev->vblank_event_list, base.link) {
		if (e->pipe != pipe)
			continue;
		DRM_DEBUG("Sending premature vblank event on disable: "
			  "wanted %llu, current %llu\n",
			  e->sequence, seq);
		list_del(&e->base.link);
		drm_vblank_put(dev, pipe);
		send_vblank_event(dev, e, seq, now);
	}
	spin_unlock_irqrestore(&dev->event_lock, irqflags);

	/* Will be reset by the modeset helpers when re-enabling the crtc by
	 * calling drm_calc_timestamping_constants(). */
	vblank->hwmode.crtc_clock = 0;
}
EXPORT_SYMBOL(drm_crtc_vblank_off);

/**
 * drm_crtc_vblank_reset - reset vblank state to off on a CRTC
 * @crtc: CRTC in question
 *
 * Drivers can use this function to reset the vblank state to off at load time.
 * Drivers should use this together with the drm_crtc_vblank_off() and
 * drm_crtc_vblank_on() functions. The difference compared to
 * drm_crtc_vblank_off() is that this function doesn't save the vblank counter
 * and hence doesn't need to call any driver hooks.
 *
 * This is useful for recovering driver state e.g. on driver load, or on resume.
 */
void drm_crtc_vblank_reset(struct drm_crtc *crtc)
{
	struct drm_device *dev = crtc->dev;
	unsigned long irqflags;
	unsigned int pipe = drm_crtc_index(crtc);
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];

	spin_lock_irqsave(&dev->vbl_lock, irqflags);
	/*
	 * Prevent subsequent drm_vblank_get() from enabling the vblank
	 * interrupt by bumping the refcount.
	 */
	if (!vblank->inmodeset) {
		atomic_inc(&vblank->refcount);
		vblank->inmodeset = 1;
	}
	spin_unlock_irqrestore(&dev->vbl_lock, irqflags);

	WARN_ON(!list_empty(&dev->vblank_event_list));
}
EXPORT_SYMBOL(drm_crtc_vblank_reset);

/**
 * drm_crtc_set_max_vblank_count - configure the hw max vblank counter value
 * @crtc: CRTC in question
 * @max_vblank_count: max hardware vblank counter value
 *
 * Update the maximum hardware vblank counter value for @crtc
 * at runtime. Useful for hardware where the operation of the
 * hardware vblank counter depends on the currently active
 * display configuration.
 *
 * For example, if the hardware vblank counter does not work
 * when a specific connector is active the maximum can be set
 * to zero. And when that specific connector isn't active the
 * maximum can again be set to the appropriate non-zero value.
 *
 * If used, must be called before drm_vblank_on().
 */
void drm_crtc_set_max_vblank_count(struct drm_crtc *crtc,
				   u32 max_vblank_count)
{
	struct drm_device *dev = crtc->dev;
	unsigned int pipe = drm_crtc_index(crtc);
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];

	WARN_ON(dev->max_vblank_count);
	WARN_ON(!READ_ONCE(vblank->inmodeset));

	vblank->max_vblank_count = max_vblank_count;
}
EXPORT_SYMBOL(drm_crtc_set_max_vblank_count);

/**
 * drm_crtc_vblank_on - enable vblank events on a CRTC
 * @crtc: CRTC in question
 *
 * This functions restores the vblank interrupt state captured with
 * drm_crtc_vblank_off() again and is generally called when enabling @crtc. Note
 * that calls to drm_crtc_vblank_on() and drm_crtc_vblank_off() can be
 * unbalanced and so can also be unconditionally called in driver load code to
 * reflect the current hardware state of the crtc.
 */
void drm_crtc_vblank_on(struct drm_crtc *crtc)
{
	struct drm_device *dev = crtc->dev;
	unsigned int pipe = drm_crtc_index(crtc);
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
	unsigned long irqflags;

	if (WARN_ON(pipe >= dev->num_crtcs))
		return;

	spin_lock_irqsave(&dev->vbl_lock, irqflags);
	DRM_DEBUG_VBL("crtc %d, vblank enabled %d, inmodeset %d\n",
		      pipe, vblank->enabled, vblank->inmodeset);

	/* Drop our private "prevent drm_vblank_get" refcount */
	if (vblank->inmodeset) {
		atomic_dec(&vblank->refcount);
		vblank->inmodeset = 0;
	}

	drm_reset_vblank_timestamp(dev, pipe);

	/*
	 * re-enable interrupts if there are users left, or the
	 * user wishes vblank interrupts to be enabled all the time.
	 */
	if (atomic_read(&vblank->refcount) != 0 || drm_vblank_offdelay == 0)
		WARN_ON(drm_vblank_enable(dev, pipe));
	spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
}
EXPORT_SYMBOL(drm_crtc_vblank_on);

/**
 * drm_vblank_restore - estimate missed vblanks and update vblank count.
 * @dev: DRM device
 * @pipe: CRTC index
 *
 * Power manamement features can cause frame counter resets between vblank
 * disable and enable. Drivers can use this function in their
 * &drm_crtc_funcs.enable_vblank implementation to estimate missed vblanks since
 * the last &drm_crtc_funcs.disable_vblank using timestamps and update the
 * vblank counter.
 *
 * This function is the legacy version of drm_crtc_vblank_restore().
 */
void drm_vblank_restore(struct drm_device *dev, unsigned int pipe)
{
	ktime_t t_vblank;
	struct drm_vblank_crtc *vblank;
	int framedur_ns;
	u64 diff_ns;
	u32 cur_vblank, diff = 1;
	int count = DRM_TIMESTAMP_MAXRETRIES;

	if (WARN_ON(pipe >= dev->num_crtcs))
		return;

	assert_spin_locked(&dev->vbl_lock);
	assert_spin_locked(&dev->vblank_time_lock);

	vblank = &dev->vblank[pipe];
	WARN_ONCE(drm_debug_enabled(DRM_UT_VBL) && !vblank->framedur_ns,
		  "Cannot compute missed vblanks without frame duration\n");
	framedur_ns = vblank->framedur_ns;

	do {
		cur_vblank = __get_vblank_counter(dev, pipe);
		drm_get_last_vbltimestamp(dev, pipe, &t_vblank, false);
	} while (cur_vblank != __get_vblank_counter(dev, pipe) && --count > 0);

	diff_ns = ktime_to_ns(ktime_sub(t_vblank, vblank->time));
	if (framedur_ns)
		diff = DIV_ROUND_CLOSEST_ULL(diff_ns, framedur_ns);


	DRM_DEBUG_VBL("missed %d vblanks in %lld ns, frame duration=%d ns, hw_diff=%d\n",
		      diff, diff_ns, framedur_ns, cur_vblank - vblank->last);
	store_vblank(dev, pipe, diff, t_vblank, cur_vblank);
}
EXPORT_SYMBOL(drm_vblank_restore);

/**
 * drm_crtc_vblank_restore - estimate missed vblanks and update vblank count.
 * @crtc: CRTC in question
 *
 * Power manamement features can cause frame counter resets between vblank
 * disable and enable. Drivers can use this function in their
 * &drm_crtc_funcs.enable_vblank implementation to estimate missed vblanks since
 * the last &drm_crtc_funcs.disable_vblank using timestamps and update the
 * vblank counter.
 */
void drm_crtc_vblank_restore(struct drm_crtc *crtc)
{
	drm_vblank_restore(crtc->dev, drm_crtc_index(crtc));
}
EXPORT_SYMBOL(drm_crtc_vblank_restore);

static void drm_legacy_vblank_pre_modeset(struct drm_device *dev,
					  unsigned int pipe)
{
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];

	/* vblank is not initialized (IRQ not installed ?), or has been freed */
	if (!dev->num_crtcs)
		return;

	if (WARN_ON(pipe >= dev->num_crtcs))
		return;

	/*
	 * To avoid all the problems that might happen if interrupts
	 * were enabled/disabled around or between these calls, we just
	 * have the kernel take a reference on the CRTC (just once though
	 * to avoid corrupting the count if multiple, mismatch calls occur),
	 * so that interrupts remain enabled in the interim.
	 */
	if (!vblank->inmodeset) {
		vblank->inmodeset = 0x1;
		if (drm_vblank_get(dev, pipe) == 0)
			vblank->inmodeset |= 0x2;
	}
}

static void drm_legacy_vblank_post_modeset(struct drm_device *dev,
					   unsigned int pipe)
{
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
	unsigned long irqflags;

	/* vblank is not initialized (IRQ not installed ?), or has been freed */
	if (!dev->num_crtcs)
		return;

	if (WARN_ON(pipe >= dev->num_crtcs))
		return;

	if (vblank->inmodeset) {
		spin_lock_irqsave(&dev->vbl_lock, irqflags);
		drm_reset_vblank_timestamp(dev, pipe);
		spin_unlock_irqrestore(&dev->vbl_lock, irqflags);

		if (vblank->inmodeset & 0x2)
			drm_vblank_put(dev, pipe);

		vblank->inmodeset = 0;
	}
}

int drm_legacy_modeset_ctl_ioctl(struct drm_device *dev, void *data,
				 struct drm_file *file_priv)
{
	struct drm_modeset_ctl *modeset = data;
	unsigned int pipe;

	/* If drm_vblank_init() hasn't been called yet, just no-op */
	if (!dev->num_crtcs)
		return 0;

	/* KMS drivers handle this internally */
	if (!drm_core_check_feature(dev, DRIVER_LEGACY))
		return 0;

	pipe = modeset->crtc;
	if (pipe >= dev->num_crtcs)
		return -EINVAL;

	switch (modeset->cmd) {
	case _DRM_PRE_MODESET:
		drm_legacy_vblank_pre_modeset(dev, pipe);
		break;
	case _DRM_POST_MODESET:
		drm_legacy_vblank_post_modeset(dev, pipe);
		break;
	default:
		return -EINVAL;
	}

	return 0;
}

static inline bool vblank_passed(u64 seq, u64 ref)
{
	return (seq - ref) <= (1 << 23);
}

static int drm_queue_vblank_event(struct drm_device *dev, unsigned int pipe,
				  u64 req_seq,
				  union drm_wait_vblank *vblwait,
				  struct drm_file *file_priv)
{
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
	struct drm_pending_vblank_event *e;
	ktime_t now;
	unsigned long flags;
	u64 seq;
	int ret;

	e = kzalloc(sizeof(*e), GFP_KERNEL);
	if (e == NULL) {
		ret = -ENOMEM;
		goto err_put;
	}

	e->pipe = pipe;
	e->event.base.type = DRM_EVENT_VBLANK;
	e->event.base.length = sizeof(e->event.vbl);
	e->event.vbl.user_data = vblwait->request.signal;
	e->event.vbl.crtc_id = 0;
	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
		struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
		if (crtc)
			e->event.vbl.crtc_id = crtc->base.id;
	}

	spin_lock_irqsave(&dev->event_lock, flags);

	/*
	 * drm_crtc_vblank_off() might have been called after we called
	 * drm_vblank_get(). drm_crtc_vblank_off() holds event_lock around the
	 * vblank disable, so no need for further locking.  The reference from
	 * drm_vblank_get() protects against vblank disable from another source.
	 */
	if (!READ_ONCE(vblank->enabled)) {
		ret = -EINVAL;
		goto err_unlock;
	}

	ret = drm_event_reserve_init_locked(dev, file_priv, &e->base,
					    &e->event.base);

	if (ret)
		goto err_unlock;

	seq = drm_vblank_count_and_time(dev, pipe, &now);

	DRM_DEBUG("event on vblank count %llu, current %llu, crtc %u\n",
		  req_seq, seq, pipe);

	trace_drm_vblank_event_queued(file_priv, pipe, req_seq);

	e->sequence = req_seq;
	if (vblank_passed(seq, req_seq)) {
		drm_vblank_put(dev, pipe);
		send_vblank_event(dev, e, seq, now);
		vblwait->reply.sequence = seq;
	} else {
		/* drm_handle_vblank_events will call drm_vblank_put */
		list_add_tail(&e->base.link, &dev->vblank_event_list);
		vblwait->reply.sequence = req_seq;
	}

	spin_unlock_irqrestore(&dev->event_lock, flags);

	return 0;

err_unlock:
	spin_unlock_irqrestore(&dev->event_lock, flags);
	kfree(e);
err_put:
	drm_vblank_put(dev, pipe);
	return ret;
}

static bool drm_wait_vblank_is_query(union drm_wait_vblank *vblwait)
{
	if (vblwait->request.sequence)
		return false;

	return _DRM_VBLANK_RELATIVE ==
		(vblwait->request.type & (_DRM_VBLANK_TYPES_MASK |
					  _DRM_VBLANK_EVENT |
					  _DRM_VBLANK_NEXTONMISS));
}

/*
 * Widen a 32-bit param to 64-bits.
 *
 * \param narrow 32-bit value (missing upper 32 bits)
 * \param near 64-bit value that should be 'close' to near
 *
 * This function returns a 64-bit value using the lower 32-bits from
 * 'narrow' and constructing the upper 32-bits so that the result is
 * as close as possible to 'near'.
 */

static u64 widen_32_to_64(u32 narrow, u64 near)
{
	return near + (s32) (narrow - near);
}

static void drm_wait_vblank_reply(struct drm_device *dev, unsigned int pipe,
				  struct drm_wait_vblank_reply *reply)
{
	ktime_t now;
	struct timespec64 ts;

	/*
	 * drm_wait_vblank_reply is a UAPI structure that uses 'long'
	 * to store the seconds. This is safe as we always use monotonic
	 * timestamps since linux-4.15.
	 */
	reply->sequence = drm_vblank_count_and_time(dev, pipe, &now);
	ts = ktime_to_timespec64(now);
	reply->tval_sec = (u32)ts.tv_sec;
	reply->tval_usec = ts.tv_nsec / 1000;
}

int drm_wait_vblank_ioctl(struct drm_device *dev, void *data,
			  struct drm_file *file_priv)
{
	struct drm_crtc *crtc;
	struct drm_vblank_crtc *vblank;
	union drm_wait_vblank *vblwait = data;
	int ret;
	u64 req_seq, seq;
	unsigned int pipe_index;
	unsigned int flags, pipe, high_pipe;

	if (!dev->irq_enabled)
		return -EOPNOTSUPP;

	if (vblwait->request.type & _DRM_VBLANK_SIGNAL)
		return -EINVAL;

	if (vblwait->request.type &
	    ~(_DRM_VBLANK_TYPES_MASK | _DRM_VBLANK_FLAGS_MASK |
	      _DRM_VBLANK_HIGH_CRTC_MASK)) {
		DRM_DEBUG("Unsupported type value 0x%x, supported mask 0x%x\n",
			  vblwait->request.type,
			  (_DRM_VBLANK_TYPES_MASK | _DRM_VBLANK_FLAGS_MASK |
			   _DRM_VBLANK_HIGH_CRTC_MASK));
		return -EINVAL;
	}

	flags = vblwait->request.type & _DRM_VBLANK_FLAGS_MASK;
	high_pipe = (vblwait->request.type & _DRM_VBLANK_HIGH_CRTC_MASK);
	if (high_pipe)
		pipe_index = high_pipe >> _DRM_VBLANK_HIGH_CRTC_SHIFT;
	else
		pipe_index = flags & _DRM_VBLANK_SECONDARY ? 1 : 0;

	/* Convert lease-relative crtc index into global crtc index */
	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
		pipe = 0;
		drm_for_each_crtc(crtc, dev) {
			if (drm_lease_held(file_priv, crtc->base.id)) {
				if (pipe_index == 0)
					break;
				pipe_index--;
			}
			pipe++;
		}
	} else {
		pipe = pipe_index;
	}

	if (pipe >= dev->num_crtcs)
		return -EINVAL;

	vblank = &dev->vblank[pipe];

	/* If the counter is currently enabled and accurate, short-circuit
	 * queries to return the cached timestamp of the last vblank.
	 */
	if (dev->vblank_disable_immediate &&
	    drm_wait_vblank_is_query(vblwait) &&
	    READ_ONCE(vblank->enabled)) {
		drm_wait_vblank_reply(dev, pipe, &vblwait->reply);
		return 0;
	}

	ret = drm_vblank_get(dev, pipe);
	if (ret) {
		DRM_DEBUG("crtc %d failed to acquire vblank counter, %d\n", pipe, ret);
		return ret;
	}
	seq = drm_vblank_count(dev, pipe);

	switch (vblwait->request.type & _DRM_VBLANK_TYPES_MASK) {
	case _DRM_VBLANK_RELATIVE:
		req_seq = seq + vblwait->request.sequence;
		vblwait->request.sequence = req_seq;
		vblwait->request.type &= ~_DRM_VBLANK_RELATIVE;
		break;
	case _DRM_VBLANK_ABSOLUTE:
		req_seq = widen_32_to_64(vblwait->request.sequence, seq);
		break;
	default:
		ret = -EINVAL;
		goto done;
	}

	if ((flags & _DRM_VBLANK_NEXTONMISS) &&
	    vblank_passed(seq, req_seq)) {
		req_seq = seq + 1;
		vblwait->request.type &= ~_DRM_VBLANK_NEXTONMISS;
		vblwait->request.sequence = req_seq;
	}

	if (flags & _DRM_VBLANK_EVENT) {
		/* must hold on to the vblank ref until the event fires
		 * drm_vblank_put will be called asynchronously
		 */
		return drm_queue_vblank_event(dev, pipe, req_seq, vblwait, file_priv);
	}

	if (req_seq != seq) {
		int wait;

		DRM_DEBUG("waiting on vblank count %llu, crtc %u\n",
			  req_seq, pipe);
		wait = wait_event_interruptible_timeout(vblank->queue,
			vblank_passed(drm_vblank_count(dev, pipe), req_seq) ||
				      !READ_ONCE(vblank->enabled),
			msecs_to_jiffies(3000));

		switch (wait) {
		case 0:
			/* timeout */
			ret = -EBUSY;
			break;
		case -ERESTARTSYS:
			/* interrupted by signal */
			ret = -EINTR;
			break;
		default:
			ret = 0;
			break;
		}
	}

	if (ret != -EINTR) {
		drm_wait_vblank_reply(dev, pipe, &vblwait->reply);

		DRM_DEBUG("crtc %d returning %u to client\n",
			  pipe, vblwait->reply.sequence);
	} else {
		DRM_DEBUG("crtc %d vblank wait interrupted by signal\n", pipe);
	}

done:
	drm_vblank_put(dev, pipe);
	return ret;
}

static void drm_handle_vblank_events(struct drm_device *dev, unsigned int pipe)
{
	struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
	bool high_prec = false;
	struct drm_pending_vblank_event *e, *t;
	ktime_t now;
	u64 seq;

	assert_spin_locked(&dev->event_lock);

	seq = drm_vblank_count_and_time(dev, pipe, &now);

	list_for_each_entry_safe(e, t, &dev->vblank_event_list, base.link) {
		if (e->pipe != pipe)
			continue;
		if (!vblank_passed(seq, e->sequence))
			continue;

		DRM_DEBUG("vblank event on %llu, current %llu\n",
			  e->sequence, seq);

		list_del(&e->base.link);
		drm_vblank_put(dev, pipe);
		send_vblank_event(dev, e, seq, now);
	}

	if (crtc && crtc->funcs->get_vblank_timestamp)
		high_prec = true;

	trace_drm_vblank_event(pipe, seq, now, high_prec);
}

/**
 * drm_handle_vblank - handle a vblank event
 * @dev: DRM device
 * @pipe: index of CRTC where this event occurred
 *
 * Drivers should call this routine in their vblank interrupt handlers to
 * update the vblank counter and send any signals that may be pending.
 *
 * This is the legacy version of drm_crtc_handle_vblank().
 */
bool drm_handle_vblank(struct drm_device *dev, unsigned int pipe)
{
	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
	unsigned long irqflags;
	bool disable_irq;

	if (WARN_ON_ONCE(!dev->num_crtcs))
		return false;

	if (WARN_ON(pipe >= dev->num_crtcs))
		return false;

	spin_lock_irqsave(&dev->event_lock, irqflags);

	/* Need timestamp lock to prevent concurrent execution with
	 * vblank enable/disable, as this would cause inconsistent
	 * or corrupted timestamps and vblank counts.
	 */
	spin_lock(&dev->vblank_time_lock);

	/* Vblank irq handling disabled. Nothing to do. */
	if (!vblank->enabled) {
		spin_unlock(&dev->vblank_time_lock);
		spin_unlock_irqrestore(&dev->event_lock, irqflags);
		return false;
	}

	drm_update_vblank_count(dev, pipe, true);

	spin_unlock(&dev->vblank_time_lock);

	wake_up(&vblank->queue);

	/* With instant-off, we defer disabling the interrupt until after
	 * we finish processing the following vblank after all events have
	 * been signaled. The disable has to be last (after
	 * drm_handle_vblank_events) so that the timestamp is always accurate.
	 */
	disable_irq = (dev->vblank_disable_immediate &&
		       drm_vblank_offdelay > 0 &&
		       !atomic_read(&vblank->refcount));

	drm_handle_vblank_events(dev, pipe);

	spin_unlock_irqrestore(&dev->event_lock, irqflags);

	if (disable_irq)
		vblank_disable_fn(&vblank->disable_timer);

	return true;
}
EXPORT_SYMBOL(drm_handle_vblank);

/**
 * drm_crtc_handle_vblank - handle a vblank event
 * @crtc: where this event occurred
 *
 * Drivers should call this routine in their vblank interrupt handlers to
 * update the vblank counter and send any signals that may be pending.
 *
 * This is the native KMS version of drm_handle_vblank().
 *
 * Note that for a given vblank counter value drm_crtc_handle_vblank()
 * and drm_crtc_vblank_count() or drm_crtc_vblank_count_and_time()
 * provide a barrier: Any writes done before calling
 * drm_crtc_handle_vblank() will be visible to callers of the later
 * functions, iff the vblank count is the same or a later one.
 *
 * See also &drm_vblank_crtc.count.
 *
 * Returns:
 * True if the event was successfully handled, false on failure.
 */
bool drm_crtc_handle_vblank(struct drm_crtc *crtc)
{
	return drm_handle_vblank(crtc->dev, drm_crtc_index(crtc));
}
EXPORT_SYMBOL(drm_crtc_handle_vblank);

/*
 * Get crtc VBLANK count.
 *
 * \param dev DRM device
 * \param data user arguement, pointing to a drm_crtc_get_sequence structure.
 * \param file_priv drm file private for the user's open file descriptor
 */

int drm_crtc_get_sequence_ioctl(struct drm_device *dev, void *data,
				struct drm_file *file_priv)
{
	struct drm_crtc *crtc;
	struct drm_vblank_crtc *vblank;
	int pipe;
	struct drm_crtc_get_sequence *get_seq = data;
	ktime_t now;
	bool vblank_enabled;
	int ret;

	if (!drm_core_check_feature(dev, DRIVER_MODESET))
		return -EOPNOTSUPP;

	if (!dev->irq_enabled)
		return -EOPNOTSUPP;

	crtc = drm_crtc_find(dev, file_priv, get_seq->crtc_id);
	if (!crtc)
		return -ENOENT;

	pipe = drm_crtc_index(crtc);

	vblank = &dev->vblank[pipe];
	vblank_enabled = dev->vblank_disable_immediate && READ_ONCE(vblank->enabled);

	if (!vblank_enabled) {
		ret = drm_crtc_vblank_get(crtc);
		if (ret) {
			DRM_DEBUG("crtc %d failed to acquire vblank counter, %d\n", pipe, ret);
			return ret;
		}
	}
	drm_modeset_lock(&crtc->mutex, NULL);
	if (crtc->state)
		get_seq->active = crtc->state->enable;
	else
		get_seq->active = crtc->enabled;
	drm_modeset_unlock(&crtc->mutex);
	get_seq->sequence = drm_vblank_count_and_time(dev, pipe, &now);
	get_seq->sequence_ns = ktime_to_ns(now);
	if (!vblank_enabled)
		drm_crtc_vblank_put(crtc);
	return 0;
}

/*
 * Queue a event for VBLANK sequence
 *
 * \param dev DRM device
 * \param data user arguement, pointing to a drm_crtc_queue_sequence structure.
 * \param file_priv drm file private for the user's open file descriptor
 */

int drm_crtc_queue_sequence_ioctl(struct drm_device *dev, void *data,
				  struct drm_file *file_priv)
{
	struct drm_crtc *crtc;
	struct drm_vblank_crtc *vblank;
	int pipe;
	struct drm_crtc_queue_sequence *queue_seq = data;
	ktime_t now;
	struct drm_pending_vblank_event *e;
	u32 flags;
	u64 seq;
	u64 req_seq;
	int ret;
	unsigned long spin_flags;

	if (!drm_core_check_feature(dev, DRIVER_MODESET))
		return -EOPNOTSUPP;

	if (!dev->irq_enabled)
		return -EOPNOTSUPP;

	crtc = drm_crtc_find(dev, file_priv, queue_seq->crtc_id);
	if (!crtc)
		return -ENOENT;

	flags = queue_seq->flags;
	/* Check valid flag bits */
	if (flags & ~(DRM_CRTC_SEQUENCE_RELATIVE|
		      DRM_CRTC_SEQUENCE_NEXT_ON_MISS))
		return -EINVAL;

	pipe = drm_crtc_index(crtc);

	vblank = &dev->vblank[pipe];

	e = kzalloc(sizeof(*e), GFP_KERNEL);
	if (e == NULL)
		return -ENOMEM;

	ret = drm_crtc_vblank_get(crtc);
	if (ret) {
		DRM_DEBUG("crtc %d failed to acquire vblank counter, %d\n", pipe, ret);
		goto err_free;
	}

	seq = drm_vblank_count_and_time(dev, pipe, &now);
	req_seq = queue_seq->sequence;

	if (flags & DRM_CRTC_SEQUENCE_RELATIVE)
		req_seq += seq;

	if ((flags & DRM_CRTC_SEQUENCE_NEXT_ON_MISS) && vblank_passed(seq, req_seq))
		req_seq = seq + 1;

	e->pipe = pipe;
	e->event.base.type = DRM_EVENT_CRTC_SEQUENCE;
	e->event.base.length = sizeof(e->event.seq);
	e->event.seq.user_data = queue_seq->user_data;

	spin_lock_irqsave(&dev->event_lock, spin_flags);

	/*
	 * drm_crtc_vblank_off() might have been called after we called
	 * drm_crtc_vblank_get(). drm_crtc_vblank_off() holds event_lock around the
	 * vblank disable, so no need for further locking.  The reference from
	 * drm_crtc_vblank_get() protects against vblank disable from another source.
	 */
	if (!READ_ONCE(vblank->enabled)) {
		ret = -EINVAL;
		goto err_unlock;
	}

	ret = drm_event_reserve_init_locked(dev, file_priv, &e->base,
					    &e->event.base);

	if (ret)
		goto err_unlock;

	e->sequence = req_seq;

	if (vblank_passed(seq, req_seq)) {
		drm_crtc_vblank_put(crtc);
		send_vblank_event(dev, e, seq, now);
		queue_seq->sequence = seq;
	} else {
		/* drm_handle_vblank_events will call drm_vblank_put */
		list_add_tail(&e->base.link, &dev->vblank_event_list);
		queue_seq->sequence = req_seq;
	}

	spin_unlock_irqrestore(&dev->event_lock, spin_flags);
	return 0;

err_unlock:
	spin_unlock_irqrestore(&dev->event_lock, spin_flags);
	drm_crtc_vblank_put(crtc);
err_free:
	kfree(e);
	return ret;
}