[mirror_edk2.git] / PcAtChipsetPkg / 8254TimerDxe / Timer.c

/** @file\r
  Timer Architectural Protocol as defined in the DXE CIS\r
\r
Copyright (c) 2005 - 2018, Intel Corporation. All rights reserved.<BR>\r
SPDX-License-Identifier: BSD-2-Clause-Patent\r
\r
**/\r
\r
#include "Timer.h"\r
\r
//\r
// The handle onto which the Timer Architectural Protocol will be installed\r
//\r
EFI_HANDLE                mTimerHandle = NULL;\r
\r
//\r
// The Timer Architectural Protocol that this driver produces\r
//\r
EFI_TIMER_ARCH_PROTOCOL   mTimer = {\r
  TimerDriverRegisterHandler,\r
  TimerDriverSetTimerPeriod,\r
  TimerDriverGetTimerPeriod,\r
  TimerDriverGenerateSoftInterrupt\r
};\r
\r
//\r
// Pointer to the CPU Architectural Protocol instance\r
//\r
EFI_CPU_ARCH_PROTOCOL     *mCpu;\r
\r
//\r
// Pointer to the Legacy 8259 Protocol instance\r
//\r
EFI_LEGACY_8259_PROTOCOL  *mLegacy8259;\r
\r
//\r
// The notification function to call on every timer interrupt.\r
// A bug in the compiler prevents us from initializing this here.\r
//\r
EFI_TIMER_NOTIFY mTimerNotifyFunction;\r
\r
//\r
// The current period of the timer interrupt\r
//\r
volatile UINT64           mTimerPeriod = 0;\r
\r
//\r
// Worker Functions\r
//\r
/**\r
  Sets the counter value for Timer #0 in a legacy 8254 timer.\r
\r
  @param Count    The 16-bit counter value to program into Timer #0 of the legacy 8254 timer.\r
**/\r
VOID\r
SetPitCount (\r
  IN UINT16  Count\r
  )\r
{\r
  IoWrite8 (TIMER_CONTROL_PORT, 0x36);\r
  IoWrite8 (TIMER0_COUNT_PORT, (UINT8)(Count & 0xff));\r
  IoWrite8 (TIMER0_COUNT_PORT, (UINT8)((Count >> 8) & 0xff));\r
}\r
\r
/**\r
  8254 Timer #0 Interrupt Handler.\r
\r
  @param InterruptType    The type of interrupt that occurred\r
  @param SystemContext    A pointer to the system context when the interrupt occurred\r
**/\r
VOID\r
EFIAPI\r
TimerInterruptHandler (\r
  IN EFI_EXCEPTION_TYPE   InterruptType,\r
  IN EFI_SYSTEM_CONTEXT   SystemContext\r
  )\r
{\r
  EFI_TPL OriginalTPL;\r
\r
  OriginalTPL = gBS->RaiseTPL (TPL_HIGH_LEVEL);\r
\r
  mLegacy8259->EndOfInterrupt (mLegacy8259, Efi8259Irq0);\r
\r
  if (mTimerNotifyFunction != NULL) {\r
    //\r
    // @bug : This does not handle missed timer interrupts\r
    //\r
    mTimerNotifyFunction (mTimerPeriod);\r
  }\r
\r
  gBS->RestoreTPL (OriginalTPL);\r
}\r
\r
/**\r
\r
  This function registers the handler NotifyFunction so it is called every time\r
  the timer interrupt fires.  It also passes the amount of time since the last\r
  handler call to the NotifyFunction.  If NotifyFunction is NULL, then the\r
  handler is unregistered.  If the handler is registered, then EFI_SUCCESS is\r
  returned.  If the CPU does not support registering a timer interrupt handler,\r
  then EFI_UNSUPPORTED is returned.  If an attempt is made to register a handler\r
  when a handler is already registered, then EFI_ALREADY_STARTED is returned.\r
  If an attempt is made to unregister a handler when a handler is not registered,\r
  then EFI_INVALID_PARAMETER is returned.  If an error occurs attempting to\r
  register the NotifyFunction with the timer interrupt, then EFI_DEVICE_ERROR\r
  is returned.\r
\r
\r
  @param This             The EFI_TIMER_ARCH_PROTOCOL instance.\r
  @param NotifyFunction   The function to call when a timer interrupt fires.  This\r
                          function executes at TPL_HIGH_LEVEL.  The DXE Core will\r
                          register a handler for the timer interrupt, so it can know\r
                          how much time has passed.  This information is used to\r
                          signal timer based events.  NULL will unregister the handler.\r
\r
  @retval        EFI_SUCCESS            The timer handler was registered.\r
  @retval        EFI_UNSUPPORTED        The platform does not support timer interrupts.\r
  @retval        EFI_ALREADY_STARTED    NotifyFunction is not NULL, and a handler is already\r
                                        registered.\r
  @retval        EFI_INVALID_PARAMETER  NotifyFunction is NULL, and a handler was not\r
                                        previously registered.\r
  @retval        EFI_DEVICE_ERROR       The timer handler could not be registered.\r
\r
**/\r
EFI_STATUS\r
EFIAPI\r
TimerDriverRegisterHandler (\r
  IN EFI_TIMER_ARCH_PROTOCOL  *This,\r
  IN EFI_TIMER_NOTIFY         NotifyFunction\r
  )\r
{\r
  //\r
  // Check for invalid parameters\r
  //\r
  if (NotifyFunction == NULL && mTimerNotifyFunction == NULL) {\r
    return EFI_INVALID_PARAMETER;\r
  }\r
\r
  if (NotifyFunction != NULL && mTimerNotifyFunction != NULL) {\r
    return EFI_ALREADY_STARTED;\r
  }\r
\r
  mTimerNotifyFunction = NotifyFunction;\r
\r
  return EFI_SUCCESS;\r
}\r
\r
/**\r
\r
  This function adjusts the period of timer interrupts to the value specified\r
  by TimerPeriod.  If the timer period is updated, then the selected timer\r
  period is stored in EFI_TIMER.TimerPeriod, and EFI_SUCCESS is returned.  If\r
  the timer hardware is not programmable, then EFI_UNSUPPORTED is returned.\r
  If an error occurs while attempting to update the timer period, then the\r
  timer hardware will be put back in its state prior to this call, and\r
  EFI_DEVICE_ERROR is returned.  If TimerPeriod is 0, then the timer interrupt\r
  is disabled.  This is not the same as disabling the CPU's interrupts.\r
  Instead, it must either turn off the timer hardware, or it must adjust the\r
  interrupt controller so that a CPU interrupt is not generated when the timer\r
  interrupt fires.\r
\r
\r
  @param This            The EFI_TIMER_ARCH_PROTOCOL instance.\r
  @param TimerPeriod     The rate to program the timer interrupt in 100 nS units.  If\r
                         the timer hardware is not programmable, then EFI_UNSUPPORTED is\r
                         returned.  If the timer is programmable, then the timer period\r
                         will be rounded up to the nearest timer period that is supported\r
                         by the timer hardware.  If TimerPeriod is set to 0, then the\r
                         timer interrupts will be disabled.\r
\r
  @retval        EFI_SUCCESS       The timer period was changed.\r
  @retval        EFI_UNSUPPORTED   The platform cannot change the period of the timer interrupt.\r
  @retval        EFI_DEVICE_ERROR  The timer period could not be changed due to a device error.\r
\r
**/\r
EFI_STATUS\r
EFIAPI\r
TimerDriverSetTimerPeriod (\r
  IN EFI_TIMER_ARCH_PROTOCOL  *This,\r
  IN UINT64                   TimerPeriod\r
  )\r
{\r
  UINT64  TimerCount;\r
\r
  //\r
  //  The basic clock is 1.19318 MHz or 0.119318 ticks per 100 ns.\r
  //  TimerPeriod * 0.119318 = 8254 timer divisor. Using integer arithmetic\r
  //  TimerCount = (TimerPeriod * 119318)/1000000.\r
  //\r
  //  Round up to next highest integer. This guarantees that the timer is\r
  //  equal to or slightly longer than the requested time.\r
  //  TimerCount = ((TimerPeriod * 119318) + 500000)/1000000\r
  //\r
  // Note that a TimerCount of 0 is equivalent to a count of 65,536\r
  //\r
  // Since TimerCount is limited to 16 bits for IA32, TimerPeriod is limited\r
  // to 20 bits.\r
  //\r
  if (TimerPeriod == 0) {\r
    //\r
    // Disable timer interrupt for a TimerPeriod of 0\r
    //\r
    mLegacy8259->DisableIrq (mLegacy8259, Efi8259Irq0);\r
  } else {\r
\r
    //\r
    // Convert TimerPeriod into 8254 counts\r
    //\r
    TimerCount = DivU64x32 (MultU64x32 (119318, (UINT32) TimerPeriod) + 500000, 1000000);\r
\r
    //\r
    // Check for overflow\r
    //\r
    if (TimerCount >= 65536) {\r
      TimerCount = 0;\r
      TimerPeriod = MAX_TIMER_TICK_DURATION;\r
    }\r
    //\r
    // Program the 8254 timer with the new count value\r
    //\r
    SetPitCount ((UINT16) TimerCount);\r
\r
    //\r
    // Enable timer interrupt\r
    //\r
    mLegacy8259->EnableIrq (mLegacy8259, Efi8259Irq0, FALSE);\r
  }\r
  //\r
  // Save the new timer period\r
  //\r
  mTimerPeriod = TimerPeriod;\r
\r
  return EFI_SUCCESS;\r
}\r
\r
/**\r
\r
  This function retrieves the period of timer interrupts in 100 ns units,\r
  returns that value in TimerPeriod, and returns EFI_SUCCESS.  If TimerPeriod\r
  is NULL, then EFI_INVALID_PARAMETER is returned.  If a TimerPeriod of 0 is\r
  returned, then the timer is currently disabled.\r
\r
\r
  @param This            The EFI_TIMER_ARCH_PROTOCOL instance.\r
  @param TimerPeriod     A pointer to the timer period to retrieve in 100 ns units.  If\r
                         0 is returned, then the timer is currently disabled.\r
\r
  @retval EFI_SUCCESS            The timer period was returned in TimerPeriod.\r
  @retval EFI_INVALID_PARAMETER  TimerPeriod is NULL.\r
\r
**/\r
EFI_STATUS\r
EFIAPI\r
TimerDriverGetTimerPeriod (\r
  IN EFI_TIMER_ARCH_PROTOCOL   *This,\r
  OUT UINT64                   *TimerPeriod\r
  )\r
{\r
  if (TimerPeriod == NULL) {\r
    return EFI_INVALID_PARAMETER;\r
  }\r
\r
  *TimerPeriod = mTimerPeriod;\r
\r
  return EFI_SUCCESS;\r
}\r
\r
/**\r
\r
  This function generates a soft timer interrupt. If the platform does not support soft\r
  timer interrupts, then EFI_UNSUPPORTED is returned. Otherwise, EFI_SUCCESS is returned.\r
  If a handler has been registered through the EFI_TIMER_ARCH_PROTOCOL.RegisterHandler()\r
  service, then a soft timer interrupt will be generated. If the timer interrupt is\r
  enabled when this service is called, then the registered handler will be invoked. The\r
  registered handler should not be able to distinguish a hardware-generated timer\r
  interrupt from a software-generated timer interrupt.\r
\r
\r
  @param This              The EFI_TIMER_ARCH_PROTOCOL instance.\r
\r
  @retval EFI_SUCCESS       The soft timer interrupt was generated.\r
  @retval EFI_UNSUPPORTED   The platform does not support the generation of soft timer interrupts.\r
\r
**/\r
EFI_STATUS\r
EFIAPI\r
TimerDriverGenerateSoftInterrupt (\r
  IN EFI_TIMER_ARCH_PROTOCOL  *This\r
  )\r
{\r
  EFI_STATUS  Status;\r
  UINT16      IRQMask;\r
  EFI_TPL     OriginalTPL;\r
\r
  //\r
  // If the timer interrupt is enabled, then the registered handler will be invoked.\r
  //\r
  Status = mLegacy8259->GetMask (mLegacy8259, NULL, NULL, &IRQMask, NULL);\r
  ASSERT_EFI_ERROR (Status);\r
  if ((IRQMask & 0x1) == 0) {\r
    //\r
    // Invoke the registered handler\r
    //\r
    OriginalTPL = gBS->RaiseTPL (TPL_HIGH_LEVEL);\r
\r
    if (mTimerNotifyFunction != NULL) {\r
      //\r
      // @bug : This does not handle missed timer interrupts\r
      //\r
      mTimerNotifyFunction (mTimerPeriod);\r
    }\r
\r
    gBS->RestoreTPL (OriginalTPL);\r
  } else {\r
    return EFI_UNSUPPORTED;\r
  }\r
\r
  return EFI_SUCCESS;\r
}\r
\r
/**\r
  Initialize the Timer Architectural Protocol driver\r
\r
  @param ImageHandle     ImageHandle of the loaded driver\r
  @param SystemTable     Pointer to the System Table\r
\r
  @retval EFI_SUCCESS            Timer Architectural Protocol created\r
  @retval EFI_OUT_OF_RESOURCES   Not enough resources available to initialize driver.\r
  @retval EFI_DEVICE_ERROR       A device error occurred attempting to initialize the driver.\r
\r
**/\r
EFI_STATUS\r
EFIAPI\r
TimerDriverInitialize (\r
  IN EFI_HANDLE        ImageHandle,\r
  IN EFI_SYSTEM_TABLE  *SystemTable\r
  )\r
{\r
  EFI_STATUS  Status;\r
  UINT32      TimerVector;\r
\r
  //\r
  // Initialize the pointer to our notify function.\r
  //\r
  mTimerNotifyFunction = NULL;\r
\r
  //\r
  // Make sure the Timer Architectural Protocol is not already installed in the system\r
  //\r
  ASSERT_PROTOCOL_ALREADY_INSTALLED (NULL, &gEfiTimerArchProtocolGuid);\r
\r
  //\r
  // Find the CPU architectural protocol.\r
  //\r
  Status = gBS->LocateProtocol (&gEfiCpuArchProtocolGuid, NULL, (VOID **) &mCpu);\r
  ASSERT_EFI_ERROR (Status);\r
\r
  //\r
  // Find the Legacy8259 protocol.\r
  //\r
  Status = gBS->LocateProtocol (&gEfiLegacy8259ProtocolGuid, NULL, (VOID **) &mLegacy8259);\r
  ASSERT_EFI_ERROR (Status);\r
\r
  //\r
  // Force the timer to be disabled\r
  //\r
  Status = TimerDriverSetTimerPeriod (&mTimer, 0);\r
  ASSERT_EFI_ERROR (Status);\r
\r
  //\r
  // Get the interrupt vector number corresponding to IRQ0 from the 8259 driver\r
  //\r
  TimerVector = 0;\r
  Status      = mLegacy8259->GetVector (mLegacy8259, Efi8259Irq0, (UINT8 *) &TimerVector);\r
  ASSERT_EFI_ERROR (Status);\r
\r
  //\r
  // Install interrupt handler for 8254 Timer #0 (ISA IRQ0)\r
  //\r
  Status = mCpu->RegisterInterruptHandler (mCpu, TimerVector, TimerInterruptHandler);\r
  ASSERT_EFI_ERROR (Status);\r
\r
  //\r
  // Force the timer to be enabled at its default period\r
  //\r
  Status = TimerDriverSetTimerPeriod (&mTimer, DEFAULT_TIMER_TICK_DURATION);\r
  ASSERT_EFI_ERROR (Status);\r
\r
  //\r
  // Install the Timer Architectural Protocol onto a new handle\r
  //\r
  Status = gBS->InstallMultipleProtocolInterfaces (\r
                  &mTimerHandle,\r
                  &gEfiTimerArchProtocolGuid, &mTimer,\r
                  NULL\r
                  );\r
  ASSERT_EFI_ERROR (Status);\r
\r
  return Status;\r
}\r
\r
Commit	Line	Data
	1	/** @file\r
	2	Timer Architectural Protocol as defined in the DXE CIS\r
	3	\r
	4	Copyright (c) 2005 - 2018, Intel Corporation. All rights reserved.<BR>\r
	5	SPDX-License-Identifier: BSD-2-Clause-Patent\r
	6	\r
	7	**/\r
	8	\r
	9	#include "Timer.h"\r
	10	\r
	11	//\r
	12	// The handle onto which the Timer Architectural Protocol will be installed\r
	13	//\r
	14	EFI_HANDLE mTimerHandle = NULL;\r
	15	\r
	16	//\r
	17	// The Timer Architectural Protocol that this driver produces\r
	18	//\r
	19	EFI_TIMER_ARCH_PROTOCOL mTimer = {\r
	20	TimerDriverRegisterHandler,\r
	21	TimerDriverSetTimerPeriod,\r
	22	TimerDriverGetTimerPeriod,\r
	23	TimerDriverGenerateSoftInterrupt\r
	24	};\r
	25	\r
	26	//\r
	27	// Pointer to the CPU Architectural Protocol instance\r
	28	//\r
	29	EFI_CPU_ARCH_PROTOCOL *mCpu;\r
	30	\r
	31	//\r
	32	// Pointer to the Legacy 8259 Protocol instance\r
	33	//\r
	34	EFI_LEGACY_8259_PROTOCOL *mLegacy8259;\r
	35	\r
	36	//\r
	37	// The notification function to call on every timer interrupt.\r
	38	// A bug in the compiler prevents us from initializing this here.\r
	39	//\r
	40	EFI_TIMER_NOTIFY mTimerNotifyFunction;\r
	41	\r
	42	//\r
	43	// The current period of the timer interrupt\r
	44	//\r
	45	volatile UINT64 mTimerPeriod = 0;\r
	46	\r
	47	//\r
	48	// Worker Functions\r
	49	//\r
	50	/**\r
	51	Sets the counter value for Timer #0 in a legacy 8254 timer.\r
	52	\r
	53	@param Count The 16-bit counter value to program into Timer #0 of the legacy 8254 timer.\r
	54	**/\r
	55	VOID\r
	56	SetPitCount (\r
	57	IN UINT16 Count\r
	58	)\r
	59	{\r
	60	IoWrite8 (TIMER_CONTROL_PORT, 0x36);\r
	61	IoWrite8 (TIMER0_COUNT_PORT, (UINT8)(Count & 0xff));\r
	62	IoWrite8 (TIMER0_COUNT_PORT, (UINT8)((Count >> 8) & 0xff));\r
	63	}\r
	64	\r
	65	/**\r
	66	8254 Timer #0 Interrupt Handler.\r
	67	\r
	68	@param InterruptType The type of interrupt that occurred\r
	69	@param SystemContext A pointer to the system context when the interrupt occurred\r
	70	**/\r
	71	VOID\r
	72	EFIAPI\r
	73	TimerInterruptHandler (\r
	74	IN EFI_EXCEPTION_TYPE InterruptType,\r
	75	IN EFI_SYSTEM_CONTEXT SystemContext\r
	76	)\r
	77	{\r
	78	EFI_TPL OriginalTPL;\r
	79	\r
	80	OriginalTPL = gBS->RaiseTPL (TPL_HIGH_LEVEL);\r
	81	\r
	82	mLegacy8259->EndOfInterrupt (mLegacy8259, Efi8259Irq0);\r
	83	\r
	84	if (mTimerNotifyFunction != NULL) {\r
	85	//\r
	86	// @bug : This does not handle missed timer interrupts\r
	87	//\r
	88	mTimerNotifyFunction (mTimerPeriod);\r
	89	}\r
	90	\r
	91	gBS->RestoreTPL (OriginalTPL);\r
	92	}\r
	93	\r
	94	/**\r
	95	\r
	96	This function registers the handler NotifyFunction so it is called every time\r
	97	the timer interrupt fires. It also passes the amount of time since the last\r
	98	handler call to the NotifyFunction. If NotifyFunction is NULL, then the\r
	99	handler is unregistered. If the handler is registered, then EFI_SUCCESS is\r
	100	returned. If the CPU does not support registering a timer interrupt handler,\r
	101	then EFI_UNSUPPORTED is returned. If an attempt is made to register a handler\r
	102	when a handler is already registered, then EFI_ALREADY_STARTED is returned.\r
	103	If an attempt is made to unregister a handler when a handler is not registered,\r
	104	then EFI_INVALID_PARAMETER is returned. If an error occurs attempting to\r
	105	register the NotifyFunction with the timer interrupt, then EFI_DEVICE_ERROR\r
	106	is returned.\r
	107	\r
	108	\r
	109	@param This The EFI_TIMER_ARCH_PROTOCOL instance.\r
	110	@param NotifyFunction The function to call when a timer interrupt fires. This\r
	111	function executes at TPL_HIGH_LEVEL. The DXE Core will\r
	112	register a handler for the timer interrupt, so it can know\r
	113	how much time has passed. This information is used to\r
	114	signal timer based events. NULL will unregister the handler.\r
	115	\r
	116	@retval EFI_SUCCESS The timer handler was registered.\r
	117	@retval EFI_UNSUPPORTED The platform does not support timer interrupts.\r
	118	@retval EFI_ALREADY_STARTED NotifyFunction is not NULL, and a handler is already\r
	119	registered.\r
	120	@retval EFI_INVALID_PARAMETER NotifyFunction is NULL, and a handler was not\r
	121	previously registered.\r
	122	@retval EFI_DEVICE_ERROR The timer handler could not be registered.\r
	123	\r
	124	**/\r
	125	EFI_STATUS\r
	126	EFIAPI\r
	127	TimerDriverRegisterHandler (\r
	128	IN EFI_TIMER_ARCH_PROTOCOL *This,\r
	129	IN EFI_TIMER_NOTIFY NotifyFunction\r
	130	)\r
	131	{\r
	132	//\r
	133	// Check for invalid parameters\r
	134	//\r
	135	if (NotifyFunction == NULL && mTimerNotifyFunction == NULL) {\r
	136	return EFI_INVALID_PARAMETER;\r
	137	}\r
	138	\r
	139	if (NotifyFunction != NULL && mTimerNotifyFunction != NULL) {\r
	140	return EFI_ALREADY_STARTED;\r
	141	}\r
	142	\r
	143	mTimerNotifyFunction = NotifyFunction;\r
	144	\r
	145	return EFI_SUCCESS;\r
	146	}\r
	147	\r
	148	/**\r
	149	\r
	150	This function adjusts the period of timer interrupts to the value specified\r
	151	by TimerPeriod. If the timer period is updated, then the selected timer\r
	152	period is stored in EFI_TIMER.TimerPeriod, and EFI_SUCCESS is returned. If\r
	153	the timer hardware is not programmable, then EFI_UNSUPPORTED is returned.\r
	154	If an error occurs while attempting to update the timer period, then the\r
	155	timer hardware will be put back in its state prior to this call, and\r
	156	EFI_DEVICE_ERROR is returned. If TimerPeriod is 0, then the timer interrupt\r
	157	is disabled. This is not the same as disabling the CPU's interrupts.\r
	158	Instead, it must either turn off the timer hardware, or it must adjust the\r
	159	interrupt controller so that a CPU interrupt is not generated when the timer\r
	160	interrupt fires.\r
	161	\r
	162	\r
	163	@param This The EFI_TIMER_ARCH_PROTOCOL instance.\r
	164	@param TimerPeriod The rate to program the timer interrupt in 100 nS units. If\r
	165	the timer hardware is not programmable, then EFI_UNSUPPORTED is\r
	166	returned. If the timer is programmable, then the timer period\r
	167	will be rounded up to the nearest timer period that is supported\r
	168	by the timer hardware. If TimerPeriod is set to 0, then the\r
	169	timer interrupts will be disabled.\r
	170	\r
	171	@retval EFI_SUCCESS The timer period was changed.\r
	172	@retval EFI_UNSUPPORTED The platform cannot change the period of the timer interrupt.\r
	173	@retval EFI_DEVICE_ERROR The timer period could not be changed due to a device error.\r
	174	\r
	175	**/\r
	176	EFI_STATUS\r
	177	EFIAPI\r
	178	TimerDriverSetTimerPeriod (\r
	179	IN EFI_TIMER_ARCH_PROTOCOL *This,\r
	180	IN UINT64 TimerPeriod\r
	181	)\r
	182	{\r
	183	UINT64 TimerCount;\r
	184	\r
	185	//\r
	186	// The basic clock is 1.19318 MHz or 0.119318 ticks per 100 ns.\r
	187	// TimerPeriod * 0.119318 = 8254 timer divisor. Using integer arithmetic\r
	188	// TimerCount = (TimerPeriod * 119318)/1000000.\r
	189	//\r
	190	// Round up to next highest integer. This guarantees that the timer is\r
	191	// equal to or slightly longer than the requested time.\r
	192	// TimerCount = ((TimerPeriod * 119318) + 500000)/1000000\r
	193	//\r
	194	// Note that a TimerCount of 0 is equivalent to a count of 65,536\r
	195	//\r
	196	// Since TimerCount is limited to 16 bits for IA32, TimerPeriod is limited\r
	197	// to 20 bits.\r
	198	//\r
	199	if (TimerPeriod == 0) {\r
	200	//\r
	201	// Disable timer interrupt for a TimerPeriod of 0\r
	202	//\r
	203	mLegacy8259->DisableIrq (mLegacy8259, Efi8259Irq0);\r
	204	} else {\r
	205	\r
	206	//\r
	207	// Convert TimerPeriod into 8254 counts\r
	208	//\r
	209	TimerCount = DivU64x32 (MultU64x32 (119318, (UINT32) TimerPeriod) + 500000, 1000000);\r
	210	\r
	211	//\r
	212	// Check for overflow\r
	213	//\r
	214	if (TimerCount >= 65536) {\r
	215	TimerCount = 0;\r
	216	TimerPeriod = MAX_TIMER_TICK_DURATION;\r
	217	}\r
	218	//\r
	219	// Program the 8254 timer with the new count value\r
	220	//\r
	221	SetPitCount ((UINT16) TimerCount);\r
	222	\r
	223	//\r
	224	// Enable timer interrupt\r
	225	//\r
	226	mLegacy8259->EnableIrq (mLegacy8259, Efi8259Irq0, FALSE);\r
	227	}\r
	228	//\r
	229	// Save the new timer period\r
	230	//\r
	231	mTimerPeriod = TimerPeriod;\r
	232	\r
	233	return EFI_SUCCESS;\r
	234	}\r
	235	\r
	236	/**\r
	237	\r
	238	This function retrieves the period of timer interrupts in 100 ns units,\r
	239	returns that value in TimerPeriod, and returns EFI_SUCCESS. If TimerPeriod\r
	240	is NULL, then EFI_INVALID_PARAMETER is returned. If a TimerPeriod of 0 is\r
	241	returned, then the timer is currently disabled.\r
	242	\r
	243	\r
	244	@param This The EFI_TIMER_ARCH_PROTOCOL instance.\r
	245	@param TimerPeriod A pointer to the timer period to retrieve in 100 ns units. If\r
	246	0 is returned, then the timer is currently disabled.\r
	247	\r
	248	@retval EFI_SUCCESS The timer period was returned in TimerPeriod.\r
	249	@retval EFI_INVALID_PARAMETER TimerPeriod is NULL.\r
	250	\r
	251	**/\r
	252	EFI_STATUS\r
	253	EFIAPI\r
	254	TimerDriverGetTimerPeriod (\r
	255	IN EFI_TIMER_ARCH_PROTOCOL *This,\r
	256	OUT UINT64 *TimerPeriod\r
	257	)\r
	258	{\r
	259	if (TimerPeriod == NULL) {\r
	260	return EFI_INVALID_PARAMETER;\r
	261	}\r
	262	\r
	263	*TimerPeriod = mTimerPeriod;\r
	264	\r
	265	return EFI_SUCCESS;\r
	266	}\r
	267	\r
	268	/**\r
	269	\r
	270	This function generates a soft timer interrupt. If the platform does not support soft\r
	271	timer interrupts, then EFI_UNSUPPORTED is returned. Otherwise, EFI_SUCCESS is returned.\r
	272	If a handler has been registered through the EFI_TIMER_ARCH_PROTOCOL.RegisterHandler()\r
	273	service, then a soft timer interrupt will be generated. If the timer interrupt is\r
	274	enabled when this service is called, then the registered handler will be invoked. The\r
	275	registered handler should not be able to distinguish a hardware-generated timer\r
	276	interrupt from a software-generated timer interrupt.\r
	277	\r
	278	\r
	279	@param This The EFI_TIMER_ARCH_PROTOCOL instance.\r
	280	\r
	281	@retval EFI_SUCCESS The soft timer interrupt was generated.\r
	282	@retval EFI_UNSUPPORTED The platform does not support the generation of soft timer interrupts.\r
	283	\r
	284	**/\r
	285	EFI_STATUS\r
	286	EFIAPI\r
	287	TimerDriverGenerateSoftInterrupt (\r
	288	IN EFI_TIMER_ARCH_PROTOCOL *This\r
	289	)\r
	290	{\r
	291	EFI_STATUS Status;\r
	292	UINT16 IRQMask;\r
	293	EFI_TPL OriginalTPL;\r
	294	\r
	295	//\r
	296	// If the timer interrupt is enabled, then the registered handler will be invoked.\r
	297	//\r
	298	Status = mLegacy8259->GetMask (mLegacy8259, NULL, NULL, &IRQMask, NULL);\r
	299	ASSERT_EFI_ERROR (Status);\r
	300	if ((IRQMask & 0x1) == 0) {\r
	301	//\r
	302	// Invoke the registered handler\r
	303	//\r
	304	OriginalTPL = gBS->RaiseTPL (TPL_HIGH_LEVEL);\r
	305	\r
	306	if (mTimerNotifyFunction != NULL) {\r
	307	//\r
	308	// @bug : This does not handle missed timer interrupts\r
	309	//\r
	310	mTimerNotifyFunction (mTimerPeriod);\r
	311	}\r
	312	\r
	313	gBS->RestoreTPL (OriginalTPL);\r
	314	} else {\r
	315	return EFI_UNSUPPORTED;\r
	316	}\r
	317	\r
	318	return EFI_SUCCESS;\r
	319	}\r
	320	\r
	321	/**\r
	322	Initialize the Timer Architectural Protocol driver\r
	323	\r
	324	@param ImageHandle ImageHandle of the loaded driver\r
	325	@param SystemTable Pointer to the System Table\r
	326	\r
	327	@retval EFI_SUCCESS Timer Architectural Protocol created\r
	328	@retval EFI_OUT_OF_RESOURCES Not enough resources available to initialize driver.\r
	329	@retval EFI_DEVICE_ERROR A device error occurred attempting to initialize the driver.\r
	330	\r
	331	**/\r
	332	EFI_STATUS\r
	333	EFIAPI\r
	334	TimerDriverInitialize (\r
	335	IN EFI_HANDLE ImageHandle,\r
	336	IN EFI_SYSTEM_TABLE *SystemTable\r
	337	)\r
	338	{\r
	339	EFI_STATUS Status;\r
	340	UINT32 TimerVector;\r
	341	\r
	342	//\r
	343	// Initialize the pointer to our notify function.\r
	344	//\r
	345	mTimerNotifyFunction = NULL;\r
	346	\r
	347	//\r
	348	// Make sure the Timer Architectural Protocol is not already installed in the system\r
	349	//\r
	350	ASSERT_PROTOCOL_ALREADY_INSTALLED (NULL, &gEfiTimerArchProtocolGuid);\r
	351	\r
	352	//\r
	353	// Find the CPU architectural protocol.\r
	354	//\r
	355	Status = gBS->LocateProtocol (&gEfiCpuArchProtocolGuid, NULL, (VOID **) &mCpu);\r
	356	ASSERT_EFI_ERROR (Status);\r
	357	\r
	358	//\r
	359	// Find the Legacy8259 protocol.\r
	360	//\r
	361	Status = gBS->LocateProtocol (&gEfiLegacy8259ProtocolGuid, NULL, (VOID **) &mLegacy8259);\r
	362	ASSERT_EFI_ERROR (Status);\r
	363	\r
	364	//\r
	365	// Force the timer to be disabled\r
	366	//\r
	367	Status = TimerDriverSetTimerPeriod (&mTimer, 0);\r
	368	ASSERT_EFI_ERROR (Status);\r
	369	\r
	370	//\r
	371	// Get the interrupt vector number corresponding to IRQ0 from the 8259 driver\r
	372	//\r
	373	TimerVector = 0;\r
	374	Status = mLegacy8259->GetVector (mLegacy8259, Efi8259Irq0, (UINT8 *) &TimerVector);\r
	375	ASSERT_EFI_ERROR (Status);\r
	376	\r
	377	//\r
	378	// Install interrupt handler for 8254 Timer #0 (ISA IRQ0)\r
	379	//\r
	380	Status = mCpu->RegisterInterruptHandler (mCpu, TimerVector, TimerInterruptHandler);\r
	381	ASSERT_EFI_ERROR (Status);\r
	382	\r
	383	//\r
	384	// Force the timer to be enabled at its default period\r
	385	//\r
	386	Status = TimerDriverSetTimerPeriod (&mTimer, DEFAULT_TIMER_TICK_DURATION);\r
	387	ASSERT_EFI_ERROR (Status);\r
	388	\r
	389	//\r
	390	// Install the Timer Architectural Protocol onto a new handle\r
	391	//\r
	392	Status = gBS->InstallMultipleProtocolInterfaces (\r
	393	&mTimerHandle,\r
	394	&gEfiTimerArchProtocolGuid, &mTimer,\r
	395	NULL\r
	396	);\r
	397	ASSERT_EFI_ERROR (Status);\r
	398	\r
	399	return Status;\r
	400	}\r
	401	\r