projects / mirror_edk2.git / blame
| Commit | Line | Data |
|---|---|---|
| fd501a79 LG |
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 | |
| e1d302e5 | 5 | SPDX-License-Identifier: BSD-2-Clause-Patent\r |
| fd501a79 LG |
6 | \r |
| 7 | **/\r | |
| 8 | \r | |
| 9 | #include <PiPei.h>\r | |
| 10 | #include <Library/TimerLib.h>\r | |
| 11 | #include <Library/BaseLib.h>\r | |
| 12 | #include <Library/HobLib.h>\r | |
| 8ee7ad90 | 13 | #include <Library/DebugLib.h>\r |
| fd501a79 | 14 | \r |
| 5220bd21 | 15 | extern GUID mFrequencyHobGuid;\r |
| fd501a79 LG |
16 | \r |
| 17 | /**\r | |
| 18 | Calculate TSC frequency.\r | |
| 19 | \r | |
| 20 | The TSC counting frequency is determined by comparing how far it counts\r | |
| 21 | during a 101.4 us period as determined by the ACPI timer.\r | |
| 22 | The ACPI timer is used because it counts at a known frequency.\r | |
| 23 | The TSC is sampled, followed by waiting 363 counts of the ACPI timer,\r | |
| 24 | or 101.4 us. The TSC is then sampled again. The difference multiplied by\r | |
| 25 | 9861 is the TSC frequency. There will be a small error because of the\r | |
| 26 | overhead of reading the ACPI timer. An attempt is made to determine and\r | |
| 27 | compensate for this error.\r | |
| 28 | \r | |
| 29 | @return The number of TSC counts per second.\r | |
| 30 | \r | |
| 31 | **/\r | |
| 32 | UINT64\r | |
| 33 | InternalCalculateTscFrequency (\r | |
| 34 | VOID\r | |
| 35 | );\r | |
| 36 | \r | |
| 37 | /**\r | |
| 38 | Internal function to retrieves the 64-bit frequency in Hz.\r | |
| 39 | \r | |
| 40 | Internal function to retrieves the 64-bit frequency in Hz.\r | |
| 41 | \r | |
| 42 | @return The frequency in Hz.\r | |
| 43 | \r | |
| 44 | **/\r | |
| 45 | UINT64\r | |
| 46 | InternalGetPerformanceCounterFrequency (\r | |
| 47 | VOID\r | |
| 48 | )\r | |
| 49 | {\r | |
| 5220bd21 MK |
50 | UINT64 *PerformanceCounterFrequency;\r |
| 51 | EFI_HOB_GUID_TYPE *GuidHob;\r | |
| fd501a79 LG |
52 | \r |
| 53 | PerformanceCounterFrequency = NULL;\r | |
| 5220bd21 | 54 | GuidHob = GetFirstGuidHob (&mFrequencyHobGuid);\r |
| fd501a79 | 55 | if (GuidHob == NULL) {\r |
| 5220bd21 | 56 | PerformanceCounterFrequency = (UINT64 *)BuildGuidHob (&mFrequencyHobGuid, sizeof (*PerformanceCounterFrequency));\r |
| fd501a79 LG |
57 | ASSERT (PerformanceCounterFrequency != NULL);\r |
| 58 | *PerformanceCounterFrequency = InternalCalculateTscFrequency ();\r | |
| 59 | } else {\r | |
| 5220bd21 | 60 | PerformanceCounterFrequency = (UINT64 *)GET_GUID_HOB_DATA (GuidHob);\r |
| fd501a79 LG |
61 | }\r |
| 62 | \r | |
| 5220bd21 | 63 | return *PerformanceCounterFrequency;\r |
| fd501a79 | 64 | }\r |