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79a951d1 KQ |
1 | /** @file\r |
2 | ACPI Timer implements one instance of Timer Library.\r | |
3 | \r | |
4 | Copyright (c) 2013 - 2018, Intel Corporation. All rights reserved.<BR>\r | |
5 | SPDX-License-Identifier: BSD-2-Clause-Patent\r | |
6 | \r | |
7 | **/\r | |
8 | \r | |
9 | #include <PiDxe.h>\r | |
10 | #include <Library/TimerLib.h>\r | |
11 | #include <Library/BaseLib.h>\r | |
12 | #include <Library/HobLib.h>\r | |
13 | \r | |
5220bd21 | 14 | extern GUID mFrequencyHobGuid;\r |
79a951d1 KQ |
15 | \r |
16 | /**\r | |
17 | The constructor function enables ACPI IO space.\r | |
18 | \r | |
19 | If ACPI I/O space not enabled, this function will enable it.\r | |
20 | It will always return RETURN_SUCCESS.\r | |
21 | \r | |
22 | @retval EFI_SUCCESS The constructor always returns RETURN_SUCCESS.\r | |
23 | \r | |
24 | **/\r | |
25 | RETURN_STATUS\r | |
26 | EFIAPI\r | |
27 | AcpiTimerLibConstructor (\r | |
28 | VOID\r | |
29 | );\r | |
30 | \r | |
31 | /**\r | |
32 | Calculate TSC frequency.\r | |
33 | \r | |
34 | The TSC counting frequency is determined by comparing how far it counts\r | |
35 | during a 101.4 us period as determined by the ACPI timer.\r | |
36 | The ACPI timer is used because it counts at a known frequency.\r | |
37 | The TSC is sampled, followed by waiting 363 counts of the ACPI timer,\r | |
38 | or 101.4 us. The TSC is then sampled again. The difference multiplied by\r | |
39 | 9861 is the TSC frequency. There will be a small error because of the\r | |
40 | overhead of reading the ACPI timer. An attempt is made to determine and\r | |
41 | compensate for this error.\r | |
42 | \r | |
43 | @return The number of TSC counts per second.\r | |
44 | \r | |
45 | **/\r | |
46 | UINT64\r | |
47 | InternalCalculateTscFrequency (\r | |
48 | VOID\r | |
49 | );\r | |
50 | \r | |
51 | //\r | |
52 | // Cached performance counter frequency\r | |
53 | //\r | |
54 | UINT64 mPerformanceCounterFrequency = 0;\r | |
55 | \r | |
56 | /**\r | |
57 | Internal function to retrieves the 64-bit frequency in Hz.\r | |
58 | \r | |
59 | Internal function to retrieves the 64-bit frequency in Hz.\r | |
60 | \r | |
61 | @return The frequency in Hz.\r | |
62 | \r | |
63 | **/\r | |
64 | UINT64\r | |
65 | InternalGetPerformanceCounterFrequency (\r | |
66 | VOID\r | |
67 | )\r | |
68 | {\r | |
5220bd21 | 69 | return mPerformanceCounterFrequency;\r |
79a951d1 KQ |
70 | }\r |
71 | \r | |
72 | /**\r | |
73 | The constructor function enables ACPI IO space, and caches PerformanceCounterFrequency.\r | |
74 | \r | |
75 | @retval EFI_SUCCESS The constructor always returns RETURN_SUCCESS.\r | |
76 | \r | |
77 | **/\r | |
78 | EFI_STATUS\r | |
79 | CommonAcpiTimerLibConstructor (\r | |
80 | VOID\r | |
81 | )\r | |
82 | {\r | |
5220bd21 | 83 | EFI_HOB_GUID_TYPE *GuidHob;\r |
79a951d1 KQ |
84 | \r |
85 | //\r | |
86 | // Enable ACPI IO space.\r | |
87 | //\r | |
88 | AcpiTimerLibConstructor ();\r | |
89 | \r | |
90 | //\r | |
91 | // Initialize PerformanceCounterFrequency\r | |
92 | //\r | |
93 | GuidHob = GetFirstGuidHob (&mFrequencyHobGuid);\r | |
94 | if (GuidHob != NULL) {\r | |
5220bd21 | 95 | mPerformanceCounterFrequency = *(UINT64 *)GET_GUID_HOB_DATA (GuidHob);\r |
79a951d1 KQ |
96 | } else {\r |
97 | mPerformanceCounterFrequency = InternalCalculateTscFrequency ();\r | |
98 | }\r | |
99 | \r | |
100 | return EFI_SUCCESS;\r | |
101 | }\r |