[mirror_edk2.git] / OvmfPkg / 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
/**\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
  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
  DisableInterrupts ();\r
  mLegacy8259->EndOfInterrupt (mLegacy8259, Efi8259Irq0);\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
    // 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
    //\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
  //\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,\r
                  &mTimer,\r
                  NULL\r
                  );\r
  ASSERT_EFI_ERROR (Status);\r
\r
  return Status;\r
}\r
Commit	Line	Data
1a3ffdff HW	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
ac0a286f	14	EFI_HANDLE mTimerHandle = NULL;\r
1a3ffdff HW	15	\r
	16	//\r
	17	// The Timer Architectural Protocol that this driver produces\r
	18	//\r
ac0a286f	19	EFI_TIMER_ARCH_PROTOCOL mTimer = {\r
1a3ffdff HW	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
ac0a286f	29	EFI_CPU_ARCH_PROTOCOL *mCpu;\r
1a3ffdff HW	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
ac0a286f	40	EFI_TIMER_NOTIFY mTimerNotifyFunction;\r
1a3ffdff HW	41	\r
	42	//\r
	43	// The current period of the timer interrupt\r
	44	//\r
ac0a286f	45	volatile UINT64 mTimerPeriod = 0;\r
1a3ffdff HW	46	\r
	47	//\r
	48	// Worker Functions\r
	49	//\r
ac0a286f	50	\r
1a3ffdff HW	51	/**\r
	52	Sets the counter value for Timer #0 in a legacy 8254 timer.\r
	53	\r
	54	@param Count The 16-bit counter value to program into Timer #0 of the legacy 8254 timer.\r
	55	**/\r
	56	VOID\r
	57	SetPitCount (\r
	58	IN UINT16 Count\r
	59	)\r
	60	{\r
	61	IoWrite8 (TIMER_CONTROL_PORT, 0x36);\r
	62	IoWrite8 (TIMER0_COUNT_PORT, (UINT8)(Count & 0xff));\r
	63	IoWrite8 (TIMER0_COUNT_PORT, (UINT8)((Count >> 8) & 0xff));\r
	64	}\r
	65	\r
	66	/**\r
	67	8254 Timer #0 Interrupt Handler.\r
	68	\r
	69	@param InterruptType The type of interrupt that occurred\r
	70	@param SystemContext A pointer to the system context when the interrupt occurred\r
	71	**/\r
	72	VOID\r
	73	EFIAPI\r
	74	TimerInterruptHandler (\r
ac0a286f MK	75	IN EFI_EXCEPTION_TYPE InterruptType,\r
ac0a286f MK	76	IN EFI_SYSTEM_CONTEXT SystemContext\r
1a3ffdff HW	77	)\r
1a3ffdff HW	78	{\r
ac0a286f	79	EFI_TPL OriginalTPL;\r
1a3ffdff HW	80	\r
	81	OriginalTPL = gBS->RaiseTPL (TPL_HIGH_LEVEL);\r
	82	\r
1a3ffdff HW	83	if (mTimerNotifyFunction != NULL) {\r
	84	//\r
	85	// @bug : This does not handle missed timer interrupts\r
	86	//\r
	87	mTimerNotifyFunction (mTimerPeriod);\r
	88	}\r
	89	\r
	90	gBS->RestoreTPL (OriginalTPL);\r
239b50a8 ID	91	\r
	92	DisableInterrupts ();\r
	93	mLegacy8259->EndOfInterrupt (mLegacy8259, Efi8259Irq0);\r
1a3ffdff HW	94	}\r
	95	\r
	96	/**\r
	97	\r
	98	This function registers the handler NotifyFunction so it is called every time\r
	99	the timer interrupt fires. It also passes the amount of time since the last\r
	100	handler call to the NotifyFunction. If NotifyFunction is NULL, then the\r
	101	handler is unregistered. If the handler is registered, then EFI_SUCCESS is\r
	102	returned. If the CPU does not support registering a timer interrupt handler,\r
	103	then EFI_UNSUPPORTED is returned. If an attempt is made to register a handler\r
	104	when a handler is already registered, then EFI_ALREADY_STARTED is returned.\r
	105	If an attempt is made to unregister a handler when a handler is not registered,\r
	106	then EFI_INVALID_PARAMETER is returned. If an error occurs attempting to\r
	107	register the NotifyFunction with the timer interrupt, then EFI_DEVICE_ERROR\r
	108	is returned.\r
	109	\r
	110	\r
	111	@param This The EFI_TIMER_ARCH_PROTOCOL instance.\r
	112	@param NotifyFunction The function to call when a timer interrupt fires. This\r
	113	function executes at TPL_HIGH_LEVEL. The DXE Core will\r
	114	register a handler for the timer interrupt, so it can know\r
	115	how much time has passed. This information is used to\r
	116	signal timer based events. NULL will unregister the handler.\r
	117	\r
	118	@retval EFI_SUCCESS The timer handler was registered.\r
	119	@retval EFI_UNSUPPORTED The platform does not support timer interrupts.\r
	120	@retval EFI_ALREADY_STARTED NotifyFunction is not NULL, and a handler is already\r
	121	registered.\r
	122	@retval EFI_INVALID_PARAMETER NotifyFunction is NULL, and a handler was not\r
	123	previously registered.\r
	124	@retval EFI_DEVICE_ERROR The timer handler could not be registered.\r
	125	\r
	126	**/\r
	127	EFI_STATUS\r
	128	EFIAPI\r
	129	TimerDriverRegisterHandler (\r
	130	IN EFI_TIMER_ARCH_PROTOCOL *This,\r
	131	IN EFI_TIMER_NOTIFY NotifyFunction\r
	132	)\r
	133	{\r
	134	//\r
	135	// Check for invalid parameters\r
	136	//\r
ac0a286f	137	if ((NotifyFunction == NULL) && (mTimerNotifyFunction == NULL)) {\r
1a3ffdff HW	138	return EFI_INVALID_PARAMETER;\r
	139	}\r
	140	\r
ac0a286f	141	if ((NotifyFunction != NULL) && (mTimerNotifyFunction != NULL)) {\r
1a3ffdff HW	142	return EFI_ALREADY_STARTED;\r
	143	}\r
	144	\r
	145	mTimerNotifyFunction = NotifyFunction;\r
	146	\r
	147	return EFI_SUCCESS;\r
	148	}\r
	149	\r
	150	/**\r
	151	\r
	152	This function adjusts the period of timer interrupts to the value specified\r
	153	by TimerPeriod. If the timer period is updated, then the selected timer\r
	154	period is stored in EFI_TIMER.TimerPeriod, and EFI_SUCCESS is returned. If\r
	155	the timer hardware is not programmable, then EFI_UNSUPPORTED is returned.\r
	156	If an error occurs while attempting to update the timer period, then the\r
	157	timer hardware will be put back in its state prior to this call, and\r
	158	EFI_DEVICE_ERROR is returned. If TimerPeriod is 0, then the timer interrupt\r
	159	is disabled. This is not the same as disabling the CPU's interrupts.\r
	160	Instead, it must either turn off the timer hardware, or it must adjust the\r
	161	interrupt controller so that a CPU interrupt is not generated when the timer\r
	162	interrupt fires.\r
	163	\r
	164	\r
	165	@param This The EFI_TIMER_ARCH_PROTOCOL instance.\r
	166	@param TimerPeriod The rate to program the timer interrupt in 100 nS units. If\r
	167	the timer hardware is not programmable, then EFI_UNSUPPORTED is\r
	168	returned. If the timer is programmable, then the timer period\r
	169	will be rounded up to the nearest timer period that is supported\r
	170	by the timer hardware. If TimerPeriod is set to 0, then the\r
	171	timer interrupts will be disabled.\r
	172	\r
	173	@retval EFI_SUCCESS The timer period was changed.\r
	174	@retval EFI_UNSUPPORTED The platform cannot change the period of the timer interrupt.\r
	175	@retval EFI_DEVICE_ERROR The timer period could not be changed due to a device error.\r
	176	\r
	177	**/\r
	178	EFI_STATUS\r
	179	EFIAPI\r
	180	TimerDriverSetTimerPeriod (\r
	181	IN EFI_TIMER_ARCH_PROTOCOL *This,\r
	182	IN UINT64 TimerPeriod\r
	183	)\r
	184	{\r
	185	UINT64 TimerCount;\r
	186	\r
	187	//\r
	188	// The basic clock is 1.19318 MHz or 0.119318 ticks per 100 ns.\r
	189	// TimerPeriod * 0.119318 = 8254 timer divisor. Using integer arithmetic\r
	190	// TimerCount = (TimerPeriod * 119318)/1000000.\r
	191	//\r
	192	// Round up to next highest integer. This guarantees that the timer is\r
	193	// equal to or slightly longer than the requested time.\r
	194	// TimerCount = ((TimerPeriod * 119318) + 500000)/1000000\r
	195	//\r
	196	// Note that a TimerCount of 0 is equivalent to a count of 65,536\r
	197	//\r
	198	// Since TimerCount is limited to 16 bits for IA32, TimerPeriod is limited\r
	199	// to 20 bits.\r
	200	//\r
	201	if (TimerPeriod == 0) {\r
	202	//\r
	203	// Disable timer interrupt for a TimerPeriod of 0\r
	204	//\r
	205	mLegacy8259->DisableIrq (mLegacy8259, Efi8259Irq0);\r
206	} else {\r
1a3ffdff HW	207	//\r
	208	// Convert TimerPeriod into 8254 counts\r
	209	//\r
ac0a286f	210	TimerCount = DivU64x32 (MultU64x32 (119318, (UINT32)TimerPeriod) + 500000, 1000000);\r
1a3ffdff HW	211	\r
	212	//\r
	213	// Check for overflow\r
	214	//\r
	215	if (TimerCount >= 65536) {\r
ac0a286f	216	TimerCount = 0;\r
1a3ffdff HW	217	TimerPeriod = MAX_TIMER_TICK_DURATION;\r
1a3ffdff HW	218	}\r
ac0a286f	219	\r
1a3ffdff HW	220	//\r
	221	// Program the 8254 timer with the new count value\r
	222	//\r
ac0a286f	223	SetPitCount ((UINT16)TimerCount);\r
1a3ffdff HW	224	\r
	225	//\r
	226	// Enable timer interrupt\r
	227	//\r
	228	mLegacy8259->EnableIrq (mLegacy8259, Efi8259Irq0, FALSE);\r
	229	}\r
ac0a286f	230	\r
1a3ffdff HW	231	//\r
	232	// Save the new timer period\r
	233	//\r
	234	mTimerPeriod = TimerPeriod;\r
	235	\r
	236	return EFI_SUCCESS;\r
	237	}\r
	238	\r
	239	/**\r
	240	\r
	241	This function retrieves the period of timer interrupts in 100 ns units,\r
	242	returns that value in TimerPeriod, and returns EFI_SUCCESS. If TimerPeriod\r
	243	is NULL, then EFI_INVALID_PARAMETER is returned. If a TimerPeriod of 0 is\r
	244	returned, then the timer is currently disabled.\r
	245	\r
	246	\r
	247	@param This The EFI_TIMER_ARCH_PROTOCOL instance.\r
	248	@param TimerPeriod A pointer to the timer period to retrieve in 100 ns units. If\r
	249	0 is returned, then the timer is currently disabled.\r
	250	\r
	251	@retval EFI_SUCCESS The timer period was returned in TimerPeriod.\r
	252	@retval EFI_INVALID_PARAMETER TimerPeriod is NULL.\r
	253	\r
	254	**/\r
	255	EFI_STATUS\r
	256	EFIAPI\r
	257	TimerDriverGetTimerPeriod (\r
ac0a286f MK	258	IN EFI_TIMER_ARCH_PROTOCOL *This,\r
ac0a286f MK	259	OUT UINT64 *TimerPeriod\r
1a3ffdff HW	260	)\r
	261	{\r
	262	if (TimerPeriod == NULL) {\r
	263	return EFI_INVALID_PARAMETER;\r
	264	}\r
	265	\r
	266	*TimerPeriod = mTimerPeriod;\r
	267	\r
	268	return EFI_SUCCESS;\r
	269	}\r
	270	\r
	271	/**\r
	272	\r
	273	This function generates a soft timer interrupt. If the platform does not support soft\r
	274	timer interrupts, then EFI_UNSUPPORTED is returned. Otherwise, EFI_SUCCESS is returned.\r
	275	If a handler has been registered through the EFI_TIMER_ARCH_PROTOCOL.RegisterHandler()\r
	276	service, then a soft timer interrupt will be generated. If the timer interrupt is\r
	277	enabled when this service is called, then the registered handler will be invoked. The\r
	278	registered handler should not be able to distinguish a hardware-generated timer\r
	279	interrupt from a software-generated timer interrupt.\r
	280	\r
	281	\r
	282	@param This The EFI_TIMER_ARCH_PROTOCOL instance.\r
	283	\r
	284	@retval EFI_SUCCESS The soft timer interrupt was generated.\r
	285	@retval EFI_UNSUPPORTED The platform does not support the generation of soft timer interrupts.\r
	286	\r
	287	**/\r
	288	EFI_STATUS\r
	289	EFIAPI\r
	290	TimerDriverGenerateSoftInterrupt (\r
	291	IN EFI_TIMER_ARCH_PROTOCOL *This\r
	292	)\r
	293	{\r
	294	EFI_STATUS Status;\r
	295	UINT16 IRQMask;\r
	296	EFI_TPL OriginalTPL;\r
	297	\r
	298	//\r
	299	// If the timer interrupt is enabled, then the registered handler will be invoked.\r
	300	//\r
	301	Status = mLegacy8259->GetMask (mLegacy8259, NULL, NULL, &IRQMask, NULL);\r
	302	ASSERT_EFI_ERROR (Status);\r
	303	if ((IRQMask & 0x1) == 0) {\r
	304	//\r
	305	// Invoke the registered handler\r
	306	//\r
	307	OriginalTPL = gBS->RaiseTPL (TPL_HIGH_LEVEL);\r
	308	\r
	309	if (mTimerNotifyFunction != NULL) {\r
	310	//\r
	311	// @bug : This does not handle missed timer interrupts\r
	312	//\r
	313	mTimerNotifyFunction (mTimerPeriod);\r
	314	}\r
	315	\r
	316	gBS->RestoreTPL (OriginalTPL);\r
	317	} else {\r
	318	return EFI_UNSUPPORTED;\r
	319	}\r
	320	\r
	321	return EFI_SUCCESS;\r
	322	}\r
	323	\r
324	/**\r
325	Initialize the Timer Architectural Protocol driver\r
326	\r
327	@param ImageHandle ImageHandle of the loaded driver\r
328	@param SystemTable Pointer to the System Table\r
329	\r
330	@retval EFI_SUCCESS Timer Architectural Protocol created\r
331	@retval EFI_OUT_OF_RESOURCES Not enough resources available to initialize driver.\r
332	@retval EFI_DEVICE_ERROR A device error occurred attempting to initialize the driver.\r
333	\r
334	**/\r
335	EFI_STATUS\r
336	EFIAPI\r
337	TimerDriverInitialize (\r
338	IN EFI_HANDLE ImageHandle,\r
339	IN EFI_SYSTEM_TABLE *SystemTable\r
340	)\r
341	{\r
342	EFI_STATUS Status;\r
343	UINT32 TimerVector;\r
344	\r
345	//\r
346	// Initialize the pointer to our notify function.\r
347	//\r
348	mTimerNotifyFunction = NULL;\r
349	\r
350	//\r
351	// Make sure the Timer Architectural Protocol is not already installed in the system\r
352	//\r
353	ASSERT_PROTOCOL_ALREADY_INSTALLED (NULL, &gEfiTimerArchProtocolGuid);\r
354	\r
355	//\r
356	// Find the CPU architectural protocol.\r
357	//\r
ac0a286f	358	Status = gBS->LocateProtocol (&gEfiCpuArchProtocolGuid, NULL, (VOID **)&mCpu);\r
1a3ffdff HW	359	ASSERT_EFI_ERROR (Status);\r
	360	\r
	361	//\r
	362	// Find the Legacy8259 protocol.\r
	363	//\r
ac0a286f	364	Status = gBS->LocateProtocol (&gEfiLegacy8259ProtocolGuid, NULL, (VOID **)&mLegacy8259);\r
1a3ffdff HW	365	ASSERT_EFI_ERROR (Status);\r
	366	\r
	367	//\r
	368	// Force the timer to be disabled\r
	369	//\r
	370	Status = TimerDriverSetTimerPeriod (&mTimer, 0);\r
	371	ASSERT_EFI_ERROR (Status);\r
	372	\r
	373	//\r
	374	// Get the interrupt vector number corresponding to IRQ0 from the 8259 driver\r
	375	//\r
	376	TimerVector = 0;\r
ac0a286f	377	Status = mLegacy8259->GetVector (mLegacy8259, Efi8259Irq0, (UINT8 *)&TimerVector);\r
1a3ffdff HW	378	ASSERT_EFI_ERROR (Status);\r
	379	\r
	380	//\r
	381	// Install interrupt handler for 8254 Timer #0 (ISA IRQ0)\r
	382	//\r
	383	Status = mCpu->RegisterInterruptHandler (mCpu, TimerVector, TimerInterruptHandler);\r
	384	ASSERT_EFI_ERROR (Status);\r
	385	\r
	386	//\r
	387	// Force the timer to be enabled at its default period\r
	388	//\r
	389	Status = TimerDriverSetTimerPeriod (&mTimer, DEFAULT_TIMER_TICK_DURATION);\r
	390	ASSERT_EFI_ERROR (Status);\r
	391	\r
	392	//\r
	393	// Install the Timer Architectural Protocol onto a new handle\r
	394	//\r
	395	Status = gBS->InstallMultipleProtocolInterfaces (\r
	396	&mTimerHandle,\r
ac0a286f MK	397	&gEfiTimerArchProtocolGuid,\r
ac0a286f MK	398	&mTimer,\r
1a3ffdff HW	399	NULL\r
	400	);\r
	401	ASSERT_EFI_ERROR (Status);\r
	402	\r
	403	return Status;\r
	404	}\r