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1 | /** @file\r | |
2 | UEFI Miscellaneous boot Services Stall service implementation\r | |
3 | \r | |
4 | Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>\r | |
5 | SPDX-License-Identifier: BSD-2-Clause-Patent\r | |
6 | \r | |
7 | **/\r | |
8 | \r | |
9 | //\r | |
10 | // Include statements\r | |
11 | //\r | |
12 | \r | |
13 | #include "DxeMain.h"\r | |
14 | \r | |
15 | /**\r | |
16 | Internal worker function to call the Metronome Architectural Protocol for\r | |
17 | the number of ticks specified by the UINT64 Counter value. WaitForTick()\r | |
18 | service of the Metronome Architectural Protocol uses a UINT32 for the number\r | |
19 | of ticks to wait, so this function loops when Counter is larger than 0xffffffff.\r | |
20 | \r | |
21 | @param Counter Number of ticks to wait.\r | |
22 | \r | |
23 | **/\r | |
24 | VOID\r | |
25 | CoreInternalWaitForTick (\r | |
26 | IN UINT64 Counter\r | |
27 | )\r | |
28 | {\r | |
29 | while (RShiftU64 (Counter, 32) > 0) {\r | |
30 | gMetronome->WaitForTick (gMetronome, 0xffffffff);\r | |
31 | Counter -= 0xffffffff;\r | |
32 | }\r | |
33 | \r | |
34 | gMetronome->WaitForTick (gMetronome, (UINT32)Counter);\r | |
35 | }\r | |
36 | \r | |
37 | /**\r | |
38 | Introduces a fine-grained stall.\r | |
39 | \r | |
40 | @param Microseconds The number of microseconds to stall execution.\r | |
41 | \r | |
42 | @retval EFI_SUCCESS Execution was stalled for at least the requested\r | |
43 | amount of microseconds.\r | |
44 | @retval EFI_NOT_AVAILABLE_YET gMetronome is not available yet\r | |
45 | \r | |
46 | **/\r | |
47 | EFI_STATUS\r | |
48 | EFIAPI\r | |
49 | CoreStall (\r | |
50 | IN UINTN Microseconds\r | |
51 | )\r | |
52 | {\r | |
53 | UINT64 Counter;\r | |
54 | UINT32 Remainder;\r | |
55 | UINTN Index;\r | |
56 | \r | |
57 | if (gMetronome == NULL) {\r | |
58 | return EFI_NOT_AVAILABLE_YET;\r | |
59 | }\r | |
60 | \r | |
61 | //\r | |
62 | // Counter = Microseconds * 10 / gMetronome->TickPeriod\r | |
63 | // 0x1999999999999999 = (2^64 - 1) / 10\r | |
64 | //\r | |
65 | if ((UINT64)Microseconds > 0x1999999999999999ULL) {\r | |
66 | //\r | |
67 | // Microseconds is too large to multiple by 10 first. Perform the divide\r | |
68 | // operation first and loop 10 times to avoid 64-bit math overflow.\r | |
69 | //\r | |
70 | Counter = DivU64x32Remainder (\r | |
71 | Microseconds,\r | |
72 | gMetronome->TickPeriod,\r | |
73 | &Remainder\r | |
74 | );\r | |
75 | for (Index = 0; Index < 10; Index++) {\r | |
76 | CoreInternalWaitForTick (Counter);\r | |
77 | }\r | |
78 | \r | |
79 | if (Remainder != 0) {\r | |
80 | //\r | |
81 | // If Remainder was not zero, then normally, Counter would be rounded\r | |
82 | // up by 1 tick. In this case, since a loop for 10 counts was used\r | |
83 | // to emulate the multiply by 10 operation, Counter needs to be rounded\r | |
84 | // up by 10 counts.\r | |
85 | //\r | |
86 | CoreInternalWaitForTick (10);\r | |
87 | }\r | |
88 | } else {\r | |
89 | //\r | |
90 | // Calculate the number of ticks by dividing the number of microseconds by\r | |
91 | // the TickPeriod. Calculation is based on 100ns unit.\r | |
92 | //\r | |
93 | Counter = DivU64x32Remainder (\r | |
94 | MultU64x32 (Microseconds, 10),\r | |
95 | gMetronome->TickPeriod,\r | |
96 | &Remainder\r | |
97 | );\r | |
98 | if (Remainder != 0) {\r | |
99 | //\r | |
100 | // If Remainder is not zero, then round Counter up by one tick.\r | |
101 | //\r | |
102 | Counter++;\r | |
103 | }\r | |
104 | \r | |
105 | CoreInternalWaitForTick (Counter);\r | |
106 | }\r | |
107 | \r | |
108 | return EFI_SUCCESS;\r | |
109 | }\r |