1 /** @file 2 3 Copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR> 4 Copyright (c) 2013, ARM Ltd. All rights reserved. 5 6 This program and the accompanying materials 7 are licensed and made available under the terms and conditions of the BSD License 8 which accompanies this distribution. The full text of the license may be found at 9 http://opensource.org/licenses/bsd-license.php 10 11 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, 12 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. 13 14 **/ 15 16 #include <PiDxe.h> 17 18 #include <Library/BaseLib.h> 19 #include <Library/DebugLib.h> 20 #include <Library/BaseMemoryLib.h> 21 #include <Library/UefiBootServicesTableLib.h> 22 #include <Library/UefiLib.h> 23 #include <Library/PcdLib.h> 24 #include <Library/TimerLib.h> 25 26 #include <Protocol/Metronome.h> 27 28 EFI_STATUS 29 EFIAPI 30 WaitForTick ( 31 IN EFI_METRONOME_ARCH_PROTOCOL *This, 32 IN UINT32 TickNumber 33 ); 34 35 /** 36 Interface structure for the Metronome Architectural Protocol. 37 38 @par Protocol Description: 39 This protocol provides access to a known time source in the platform to the 40 core. The core uses this known time source to produce core services that 41 require calibrated delays. 42 43 @param WaitForTick 44 Waits for a specified number of ticks from a known time source 45 in the platform. The actual time passed between entry of this 46 function and the first tick is between 0 and TickPeriod 100 nS 47 units. If you want to guarantee that at least TickPeriod time 48 has elapsed, wait for two ticks. 49 50 @param TickPeriod 51 The period of platform's known time source in 100 nS units. 52 This value on any platform must be at least 10 uS, and must not 53 exceed 200 uS. The value in this field is a constant that must 54 not be modified after the Metronome architectural protocol is 55 installed. All consumers must treat this as a read-only field. 56 57 **/ 58 EFI_METRONOME_ARCH_PROTOCOL gMetronome = { 59 WaitForTick, 60 FixedPcdGet32 (PcdMetronomeTickPeriod) 61 }; 62 63 64 /** 65 The WaitForTick() function waits for the number of ticks specified by 66 TickNumber from a known time source in the platform. If TickNumber of 67 ticks are detected, then EFI_SUCCESS is returned. The actual time passed 68 between entry of this function and the first tick is between 0 and 69 TickPeriod 100 nS units. If you want to guarantee that at least TickPeriod 70 time has elapsed, wait for two ticks. This function waits for a hardware 71 event to determine when a tick occurs. It is possible for interrupt 72 processing, or exception processing to interrupt the execution of the 73 WaitForTick() function. Depending on the hardware source for the ticks, it 74 is possible for a tick to be missed. This function cannot guarantee that 75 ticks will not be missed. If a timeout occurs waiting for the specified 76 number of ticks, then EFI_TIMEOUT is returned. 77 78 @param This The EFI_METRONOME_ARCH_PROTOCOL instance. 79 @param TickNumber Number of ticks to wait. 80 81 @retval EFI_SUCCESS The wait for the number of ticks specified by TickNumber 82 succeeded. 83 @retval EFI_TIMEOUT A timeout occurred waiting for the specified number of ticks. 84 85 **/ 86 EFI_STATUS 87 EFIAPI 88 WaitForTick ( 89 IN EFI_METRONOME_ARCH_PROTOCOL *This, 90 IN UINT32 TickNumber 91 ) 92 { 93 // 94 // Compute how long to stall the CPU. 95 // gMetronome.TickPeriod is in 100 ns units so it needs to be divided by 10 96 // to get it in microseconds units. 97 // 98 MicroSecondDelay (TickNumber * gMetronome.TickPeriod / 10); 99 return EFI_SUCCESS; 100 } 101 102 103 EFI_HANDLE gMetronomeHandle = NULL; 104 105 106 107 /** 108 Initialize the state information for the CPU Architectural Protocol 109 110 @param ImageHandle of the loaded driver 111 @param SystemTable Pointer to the System Table 112 113 @retval EFI_SUCCESS Protocol registered 114 @retval EFI_OUT_OF_RESOURCES Cannot allocate protocol data structure 115 @retval EFI_DEVICE_ERROR Hardware problems 116 117 **/ 118 EFI_STATUS 119 MetronomeInitialize ( 120 IN EFI_HANDLE ImageHandle, 121 IN EFI_SYSTEM_TABLE *SystemTable 122 ) 123 { 124 EFI_STATUS Status; 125 126 // 127 // Do any hardware init required to make WaitForTick () to work here. 128 // 129 130 Status = gBS->InstallMultipleProtocolInterfaces ( 131 &gMetronomeHandle, 132 &gEfiMetronomeArchProtocolGuid, &gMetronome, 133 NULL 134 ); 135 ASSERT_EFI_ERROR (Status); 136 137 return Status; 138 } 139 140
