/** @file
  Implement EFI RealTimeClock runtime services via Xen shared info page

  Copyright (c) 2015, Linaro Ltd. All rights reserved.<BR>

  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include <Uefi.h>
#include <PiDxe.h>
#include <Library/BaseLib.h>
#include <Library/DebugLib.h>

/**
  Converts Epoch seconds (elapsed since 1970 JANUARY 01, 00:00:00 UTC) to EFI_TIME
 **/
STATIC
VOID
EpochToEfiTime (
  IN  UINTN     EpochSeconds,
  OUT EFI_TIME  *Time
  )
{
  UINTN  a;
  UINTN  b;
  UINTN  c;
  UINTN  d;
  UINTN  g;
  UINTN  j;
  UINTN  m;
  UINTN  y;
  UINTN  da;
  UINTN  db;
  UINTN  dc;
  UINTN  dg;
  UINTN  hh;
  UINTN  mm;
  UINTN  ss;
  UINTN  J;

  J  = (EpochSeconds / 86400) + 2440588;
  j  = J + 32044;
  g  = j / 146097;
  dg = j % 146097;
  c  = (((dg / 36524) + 1) * 3) / 4;
  dc = dg - (c * 36524);
  b  = dc / 1461;
  db = dc % 1461;
  a  = (((db / 365) + 1) * 3) / 4;
  da = db - (a * 365);
  y  = (g * 400) + (c * 100) + (b * 4) + a;
  m  = (((da * 5) + 308) / 153) - 2;
  d  = da - (((m + 4) * 153) / 5) + 122;

  Time->Year  = (UINT16)(y - 4800 + ((m + 2) / 12));
  Time->Month = ((m + 2) % 12) + 1;
  Time->Day   = (UINT8)(d + 1);

  ss = EpochSeconds % 60;
  a  = (EpochSeconds - ss) / 60;
  mm = a % 60;
  b  = (a - mm) / 60;
  hh = b % 24;

  Time->Hour       = (UINT8)hh;
  Time->Minute     = (UINT8)mm;
  Time->Second     = (UINT8)ss;
  Time->Nanosecond = 0;
}

/**
  Returns the current time and date information, and the time-keeping capabilities
  of the hardware platform.

  @param  Time                  A pointer to storage to receive a snapshot of the current time.
  @param  Capabilities          An optional pointer to a buffer to receive the real time clock
                                device's capabilities.

  @retval EFI_SUCCESS           The operation completed successfully.
  @retval EFI_INVALID_PARAMETER Time is NULL.
  @retval EFI_DEVICE_ERROR      The time could not be retrieved due to hardware error.
  @retval EFI_UNSUPPORTED       This call is not supported by this platform at the time the call is made.
                                The platform should describe this runtime service as unsupported at runtime
                                via an EFI_RT_PROPERTIES_TABLE configuration table.

**/
EFI_STATUS
EFIAPI
LibGetTime (
  OUT EFI_TIME                *Time,
  OUT  EFI_TIME_CAPABILITIES  *Capabilities
  )
{
  ASSERT (Time != NULL);

  //
  // For now, there is nothing that we can do besides returning a bogus time,
  // as Xen's timekeeping uses a shared info page which cannot be shared
  // between UEFI and the OS
  //
  EpochToEfiTime (1421770011, Time);

  return EFI_SUCCESS;
}

/**
  Sets the current local time and date information.

  @param  Time                  A pointer to the current time.

  @retval EFI_SUCCESS           The operation completed successfully.
  @retval EFI_INVALID_PARAMETER A time field is out of range.
  @retval EFI_DEVICE_ERROR      The time could not be set due to hardware error.
  @retval EFI_UNSUPPORTED       This call is not supported by this platform at the time the call is made.
                                The platform should describe this runtime service as unsupported at runtime
                                via an EFI_RT_PROPERTIES_TABLE configuration table.

**/
EFI_STATUS
EFIAPI
LibSetTime (
  IN EFI_TIME  *Time
  )
{
  return EFI_DEVICE_ERROR;
}

/**
  Returns the current wakeup alarm clock setting.

  @param  Enabled               Indicates if the alarm is currently enabled or disabled.
  @param  Pending               Indicates if the alarm signal is pending and requires acknowledgement.
  @param  Time                  The current alarm setting.

  @retval EFI_SUCCESS           The alarm settings were returned.
  @retval EFI_INVALID_PARAMETER Enabled is NULL.
  @retval EFI_INVALID_PARAMETER Pending is NULL.
  @retval EFI_INVALID_PARAMETER Time is NULL.
  @retval EFI_DEVICE_ERROR      The wakeup time could not be retrieved due to a hardware error.
  @retval EFI_UNSUPPORTED       This call is not supported by this platform at the time the call is made.
                                The platform should describe this runtime service as unsupported at runtime
                                via an EFI_RT_PROPERTIES_TABLE configuration table.

**/
EFI_STATUS
EFIAPI
LibGetWakeupTime (
  OUT BOOLEAN   *Enabled,
  OUT BOOLEAN   *Pending,
  OUT EFI_TIME  *Time
  )
{
  return EFI_UNSUPPORTED;
}

/**
  Sets the system wakeup alarm clock time.

  @param  Enabled               Enable or disable the wakeup alarm.
  @param  Time                  If Enable is TRUE, the time to set the wakeup alarm for.

  @retval EFI_SUCCESS           If Enable is TRUE, then the wakeup alarm was enabled. If
                                Enable is FALSE, then the wakeup alarm was disabled.
  @retval EFI_INVALID_PARAMETER Enabled is NULL.
  @retval EFI_INVALID_PARAMETER Pending is NULL.
  @retval EFI_INVALID_PARAMETER Time is NULL.
  @retval EFI_DEVICE_ERROR      The wakeup time could not be set due to a hardware error.
  @retval EFI_UNSUPPORTED       This call is not supported by this platform at the time the call is made.
                                The platform should describe this runtime service as unsupported at runtime
                                via an EFI_RT_PROPERTIES_TABLE configuration table.

**/
EFI_STATUS
EFIAPI
LibSetWakeupTime (
  IN BOOLEAN    Enabled,
  OUT EFI_TIME  *Time
  )
{
  return EFI_UNSUPPORTED;
}

/**
  This is the declaration of an EFI image entry point. This can be the entry point to an application
  written to this specification, an EFI boot service driver, or an EFI runtime driver.

  @param  ImageHandle           Handle that identifies the loaded image.
  @param  SystemTable           System Table for this image.

  @retval EFI_SUCCESS           The operation completed successfully.

**/
EFI_STATUS
EFIAPI
LibRtcInitialize (
  IN EFI_HANDLE        ImageHandle,
  IN EFI_SYSTEM_TABLE  *SystemTable
  )
{
  return EFI_SUCCESS;
}