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