MdeModulePkg: Replace BSD License with BSD+Patent License

[mirror_edk2.git] / MdeModulePkg / Core / Dxe / Misc / Stall.c

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