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108 lines
2.9 KiB
C
108 lines
2.9 KiB
C
/** @file
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UEFI Miscellaneous boot Services Stall service implementation
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Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
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SPDX-License-Identifier: BSD-2-Clause-Patent
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**/
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//
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// Include statements
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//
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#include "DxeMain.h"
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/**
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Internal worker function to call the Metronome Architectural Protocol for
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the number of ticks specified by the UINT64 Counter value. WaitForTick()
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service of the Metronome Architectural Protocol uses a UINT32 for the number
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of ticks to wait, so this function loops when Counter is larger than 0xffffffff.
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@param Counter Number of ticks to wait.
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**/
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VOID
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CoreInternalWaitForTick (
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IN UINT64 Counter
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)
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{
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while (RShiftU64 (Counter, 32) > 0) {
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gMetronome->WaitForTick (gMetronome, 0xffffffff);
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Counter -= 0xffffffff;
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}
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gMetronome->WaitForTick (gMetronome, (UINT32)Counter);
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}
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/**
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Introduces a fine-grained stall.
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@param Microseconds The number of microseconds to stall execution.
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@retval EFI_SUCCESS Execution was stalled for at least the requested
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amount of microseconds.
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@retval EFI_NOT_AVAILABLE_YET gMetronome is not available yet
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**/
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EFI_STATUS
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EFIAPI
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CoreStall (
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IN UINTN Microseconds
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)
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{
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UINT64 Counter;
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UINT32 Remainder;
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UINTN Index;
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if (gMetronome == NULL) {
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return EFI_NOT_AVAILABLE_YET;
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}
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//
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// Counter = Microseconds * 10 / gMetronome->TickPeriod
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// 0x1999999999999999 = (2^64 - 1) / 10
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//
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if ((UINT64) Microseconds > 0x1999999999999999ULL) {
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//
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// Microseconds is too large to multiple by 10 first. Perform the divide
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// operation first and loop 10 times to avoid 64-bit math overflow.
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//
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Counter = DivU64x32Remainder (
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Microseconds,
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gMetronome->TickPeriod,
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&Remainder
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);
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for (Index = 0; Index < 10; Index++) {
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CoreInternalWaitForTick (Counter);
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}
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if (Remainder != 0) {
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//
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// If Remainder was not zero, then normally, Counter would be rounded
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// up by 1 tick. In this case, since a loop for 10 counts was used
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// to emulate the multiply by 10 operation, Counter needs to be rounded
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// up by 10 counts.
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//
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CoreInternalWaitForTick (10);
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}
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} else {
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//
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// Calculate the number of ticks by dividing the number of microseconds by
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// the TickPeriod. Calculation is based on 100ns unit.
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//
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Counter = DivU64x32Remainder (
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MultU64x32 (Microseconds, 10),
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gMetronome->TickPeriod,
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&Remainder
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);
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if (Remainder != 0) {
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//
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// If Remainder is not zero, then round Counter up by one tick.
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//
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Counter++;
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}
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CoreInternalWaitForTick (Counter);
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}
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return EFI_SUCCESS;
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}
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