OvmfPkg/8254TimerDxe/Timer.c

   1 /** @file
   2   Timer Architectural Protocol as defined in the DXE CIS
   3
   4 Copyright (c) 2005 - 2018, Intel Corporation. All rights reserved.<BR>
   5 SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9 #include "Timer.h"
  10
  11 //
  12 // The handle onto which the Timer Architectural Protocol will be installed
  13 //
  14 EFI_HANDLE  mTimerHandle = NULL;
  15
  16 //
  17 // The Timer Architectural Protocol that this driver produces
  18 //
  19 EFI_TIMER_ARCH_PROTOCOL  mTimer = {
  20   TimerDriverRegisterHandler,
  21   TimerDriverSetTimerPeriod,
  22   TimerDriverGetTimerPeriod,
  23   TimerDriverGenerateSoftInterrupt
  24 };
  25
  26 //
  27 // Pointer to the CPU Architectural Protocol instance
  28 //
  29 EFI_CPU_ARCH_PROTOCOL  *mCpu;
  30
  31 //
  32 // Pointer to the Legacy 8259 Protocol instance
  33 //
  34 EFI_LEGACY_8259_PROTOCOL  *mLegacy8259;
  35
  36 //
  37 // The notification function to call on every timer interrupt.
  38 // A bug in the compiler prevents us from initializing this here.
  39 //
  40 EFI_TIMER_NOTIFY  mTimerNotifyFunction;
  41
  42 //
  43 // The current period of the timer interrupt
  44 //
  45 volatile UINT64  mTimerPeriod = 0;
  46
  47 //
  48 // Worker Functions
  49 //
  50
  51 /**
  52   Sets the counter value for Timer #0 in a legacy 8254 timer.
  53
  54   @param Count    The 16-bit counter value to program into Timer #0 of the legacy 8254 timer.
  55 **/
  56 VOID
  57 SetPitCount (
  58   IN UINT16  Count
  59   )
  60 {
  61   IoWrite8 (TIMER_CONTROL_PORT, 0x36);
  62   IoWrite8 (TIMER0_COUNT_PORT, (UINT8)(Count & 0xff));
  63   IoWrite8 (TIMER0_COUNT_PORT, (UINT8)((Count >> 8) & 0xff));
  64 }
  65
  66 /**
  67   8254 Timer #0 Interrupt Handler.
  68
  69   @param InterruptType    The type of interrupt that occurred
  70   @param SystemContext    A pointer to the system context when the interrupt occurred
  71 **/
  72 VOID
  73 EFIAPI
  74 TimerInterruptHandler (
  75   IN EFI_EXCEPTION_TYPE  InterruptType,
  76   IN EFI_SYSTEM_CONTEXT  SystemContext
  77   )
  78 {
  79   EFI_TPL  OriginalTPL;
  80
  81   OriginalTPL = gBS->RaiseTPL (TPL_HIGH_LEVEL);
  82
  83   if (mTimerNotifyFunction != NULL) {
  84     //
  85     // @bug : This does not handle missed timer interrupts
  86     //
  87     mTimerNotifyFunction (mTimerPeriod);
  88   }
  89
  90   gBS->RestoreTPL (OriginalTPL);
  91
  92   DisableInterrupts ();
  93   mLegacy8259->EndOfInterrupt (mLegacy8259, Efi8259Irq0);
  94 }
  95
  96 /**
  97
  98   This function registers the handler NotifyFunction so it is called every time
  99   the timer interrupt fires.  It also passes the amount of time since the last
 100   handler call to the NotifyFunction.  If NotifyFunction is NULL, then the
 101   handler is unregistered.  If the handler is registered, then EFI_SUCCESS is
 102   returned.  If the CPU does not support registering a timer interrupt handler,
 103   then EFI_UNSUPPORTED is returned.  If an attempt is made to register a handler
 104   when a handler is already registered, then EFI_ALREADY_STARTED is returned.
 105   If an attempt is made to unregister a handler when a handler is not registered,
 106   then EFI_INVALID_PARAMETER is returned.  If an error occurs attempting to
 107   register the NotifyFunction with the timer interrupt, then EFI_DEVICE_ERROR
 108   is returned.
 109
 110
 111   @param This             The EFI_TIMER_ARCH_PROTOCOL instance.
 112   @param NotifyFunction   The function to call when a timer interrupt fires.  This
 113                           function executes at TPL_HIGH_LEVEL.  The DXE Core will
 114                           register a handler for the timer interrupt, so it can know
 115                           how much time has passed.  This information is used to
 116                           signal timer based events.  NULL will unregister the handler.
 117
 118   @retval        EFI_SUCCESS            The timer handler was registered.
 119   @retval        EFI_UNSUPPORTED        The platform does not support timer interrupts.
 120   @retval        EFI_ALREADY_STARTED    NotifyFunction is not NULL, and a handler is already
 121                                         registered.
 122   @retval        EFI_INVALID_PARAMETER  NotifyFunction is NULL, and a handler was not
 123                                         previously registered.
 124   @retval        EFI_DEVICE_ERROR       The timer handler could not be registered.
 125
 126 **/
 127 EFI_STATUS
 128 EFIAPI
 129 TimerDriverRegisterHandler (
 130   IN EFI_TIMER_ARCH_PROTOCOL  *This,
 131   IN EFI_TIMER_NOTIFY         NotifyFunction
 132   )
 133 {
 134   //
 135   // Check for invalid parameters
 136   //
 137   if ((NotifyFunction == NULL) && (mTimerNotifyFunction == NULL)) {
 138     return EFI_INVALID_PARAMETER;
 139   }
 140
 141   if ((NotifyFunction != NULL) && (mTimerNotifyFunction != NULL)) {
 142     return EFI_ALREADY_STARTED;
 143   }
 144
 145   mTimerNotifyFunction = NotifyFunction;
 146
 147   return EFI_SUCCESS;
 148 }
 149
 150 /**
 151
 152   This function adjusts the period of timer interrupts to the value specified
 153   by TimerPeriod.  If the timer period is updated, then the selected timer
 154   period is stored in EFI_TIMER.TimerPeriod, and EFI_SUCCESS is returned.  If
 155   the timer hardware is not programmable, then EFI_UNSUPPORTED is returned.
 156   If an error occurs while attempting to update the timer period, then the
 157   timer hardware will be put back in its state prior to this call, and
 158   EFI_DEVICE_ERROR is returned.  If TimerPeriod is 0, then the timer interrupt
 159   is disabled.  This is not the same as disabling the CPU's interrupts.
 160   Instead, it must either turn off the timer hardware, or it must adjust the
 161   interrupt controller so that a CPU interrupt is not generated when the timer
 162   interrupt fires.
 163
 164
 165   @param This            The EFI_TIMER_ARCH_PROTOCOL instance.
 166   @param TimerPeriod     The rate to program the timer interrupt in 100 nS units.  If
 167                          the timer hardware is not programmable, then EFI_UNSUPPORTED is
 168                          returned.  If the timer is programmable, then the timer period
 169                          will be rounded up to the nearest timer period that is supported
 170                          by the timer hardware.  If TimerPeriod is set to 0, then the
 171                          timer interrupts will be disabled.
 172
 173   @retval        EFI_SUCCESS       The timer period was changed.
 174   @retval        EFI_UNSUPPORTED   The platform cannot change the period of the timer interrupt.
 175   @retval        EFI_DEVICE_ERROR  The timer period could not be changed due to a device error.
 176
 177 **/
 178 EFI_STATUS
 179 EFIAPI
 180 TimerDriverSetTimerPeriod (
 181   IN EFI_TIMER_ARCH_PROTOCOL  *This,
 182   IN UINT64                   TimerPeriod
 183   )
 184 {
 185   UINT64  TimerCount;
 186
 187   //
 188   //  The basic clock is 1.19318 MHz or 0.119318 ticks per 100 ns.
 189   //  TimerPeriod * 0.119318 = 8254 timer divisor. Using integer arithmetic
 190   //  TimerCount = (TimerPeriod * 119318)/1000000.
 191   //
 192   //  Round up to next highest integer. This guarantees that the timer is
 193   //  equal to or slightly longer than the requested time.
 194   //  TimerCount = ((TimerPeriod * 119318) + 500000)/1000000
 195   //
 196   // Note that a TimerCount of 0 is equivalent to a count of 65,536
 197   //
 198   // Since TimerCount is limited to 16 bits for IA32, TimerPeriod is limited
 199   // to 20 bits.
 200   //
 201   if (TimerPeriod == 0) {
 202     //
 203     // Disable timer interrupt for a TimerPeriod of 0
 204     //
 205     mLegacy8259->DisableIrq (mLegacy8259, Efi8259Irq0);
 206   } else {
 207     //
 208     // Convert TimerPeriod into 8254 counts
 209     //
 210     TimerCount = DivU64x32 (MultU64x32 (119318, (UINT32)TimerPeriod) + 500000, 1000000);
 211
 212     //
 213     // Check for overflow
 214     //
 215     if (TimerCount >= 65536) {
 216       TimerCount  = 0;
 217       TimerPeriod = MAX_TIMER_TICK_DURATION;
 218     }
 219
 220     //
 221     // Program the 8254 timer with the new count value
 222     //
 223     SetPitCount ((UINT16)TimerCount);
 224
 225     //
 226     // Enable timer interrupt
 227     //
 228     mLegacy8259->EnableIrq (mLegacy8259, Efi8259Irq0, FALSE);
 229   }
 230
 231   //
 232   // Save the new timer period
 233   //
 234   mTimerPeriod = TimerPeriod;
 235
 236   return EFI_SUCCESS;
 237 }
 238
 239 /**
 240
 241   This function retrieves the period of timer interrupts in 100 ns units,
 242   returns that value in TimerPeriod, and returns EFI_SUCCESS.  If TimerPeriod
 243   is NULL, then EFI_INVALID_PARAMETER is returned.  If a TimerPeriod of 0 is
 244   returned, then the timer is currently disabled.
 245
 246
 247   @param This            The EFI_TIMER_ARCH_PROTOCOL instance.
 248   @param TimerPeriod     A pointer to the timer period to retrieve in 100 ns units.  If
 249                          0 is returned, then the timer is currently disabled.
 250
 251   @retval EFI_SUCCESS            The timer period was returned in TimerPeriod.
 252   @retval EFI_INVALID_PARAMETER  TimerPeriod is NULL.
 253
 254 **/
 255 EFI_STATUS
 256 EFIAPI
 257 TimerDriverGetTimerPeriod (
 258   IN EFI_TIMER_ARCH_PROTOCOL  *This,
 259   OUT UINT64                  *TimerPeriod
 260   )
 261 {
 262   if (TimerPeriod == NULL) {
 263     return EFI_INVALID_PARAMETER;
 264   }
 265
 266   *TimerPeriod = mTimerPeriod;
 267
 268   return EFI_SUCCESS;
 269 }
 270
 271 /**
 272
 273   This function generates a soft timer interrupt. If the platform does not support soft
 274   timer interrupts, then EFI_UNSUPPORTED is returned. Otherwise, EFI_SUCCESS is returned.
 275   If a handler has been registered through the EFI_TIMER_ARCH_PROTOCOL.RegisterHandler()
 276   service, then a soft timer interrupt will be generated. If the timer interrupt is
 277   enabled when this service is called, then the registered handler will be invoked. The
 278   registered handler should not be able to distinguish a hardware-generated timer
 279   interrupt from a software-generated timer interrupt.
 280
 281
 282   @param This              The EFI_TIMER_ARCH_PROTOCOL instance.
 283
 284   @retval EFI_SUCCESS       The soft timer interrupt was generated.
 285   @retval EFI_UNSUPPORTED   The platform does not support the generation of soft timer interrupts.
 286
 287 **/
 288 EFI_STATUS
 289 EFIAPI
 290 TimerDriverGenerateSoftInterrupt (
 291   IN EFI_TIMER_ARCH_PROTOCOL  *This
 292   )
 293 {
 294   EFI_STATUS  Status;
 295   UINT16      IRQMask;
 296   EFI_TPL     OriginalTPL;
 297
 298   //
 299   // If the timer interrupt is enabled, then the registered handler will be invoked.
 300   //
 301   Status = mLegacy8259->GetMask (mLegacy8259, NULL, NULL, &IRQMask, NULL);
 302   ASSERT_EFI_ERROR (Status);
 303   if ((IRQMask & 0x1) == 0) {
 304     //
 305     // Invoke the registered handler
 306     //
 307     OriginalTPL = gBS->RaiseTPL (TPL_HIGH_LEVEL);
 308
 309     if (mTimerNotifyFunction != NULL) {
 310       //
 311       // @bug : This does not handle missed timer interrupts
 312       //
 313       mTimerNotifyFunction (mTimerPeriod);
 314     }
 315
 316     gBS->RestoreTPL (OriginalTPL);
 317   } else {
 318     return EFI_UNSUPPORTED;
 319   }
 320
 321   return EFI_SUCCESS;
 322 }
 323
 324 /**
 325   Initialize the Timer Architectural Protocol driver
 326
 327   @param ImageHandle     ImageHandle of the loaded driver
 328   @param SystemTable     Pointer to the System Table
 329
 330   @retval EFI_SUCCESS            Timer Architectural Protocol created
 331   @retval EFI_OUT_OF_RESOURCES   Not enough resources available to initialize driver.
 332   @retval EFI_DEVICE_ERROR       A device error occurred attempting to initialize the driver.
 333
 334 **/
 335 EFI_STATUS
 336 EFIAPI
 337 TimerDriverInitialize (
 338   IN EFI_HANDLE        ImageHandle,
 339   IN EFI_SYSTEM_TABLE  *SystemTable
 340   )
 341 {
 342   EFI_STATUS  Status;
 343   UINT32      TimerVector;
 344
 345   //
 346   // Initialize the pointer to our notify function.
 347   //
 348   mTimerNotifyFunction = NULL;
 349
 350   //
 351   // Make sure the Timer Architectural Protocol is not already installed in the system
 352   //
 353   ASSERT_PROTOCOL_ALREADY_INSTALLED (NULL, &gEfiTimerArchProtocolGuid);
 354
 355   //
 356   // Find the CPU architectural protocol.
 357   //
 358   Status = gBS->LocateProtocol (&gEfiCpuArchProtocolGuid, NULL, (VOID **)&mCpu);
 359   ASSERT_EFI_ERROR (Status);
 360
 361   //
 362   // Find the Legacy8259 protocol.
 363   //
 364   Status = gBS->LocateProtocol (&gEfiLegacy8259ProtocolGuid, NULL, (VOID **)&mLegacy8259);
 365   ASSERT_EFI_ERROR (Status);
 366
 367   //
 368   // Force the timer to be disabled
 369   //
 370   Status = TimerDriverSetTimerPeriod (&mTimer, 0);
 371   ASSERT_EFI_ERROR (Status);
 372
 373   //
 374   // Get the interrupt vector number corresponding to IRQ0 from the 8259 driver
 375   //
 376   TimerVector = 0;
 377   Status      = mLegacy8259->GetVector (mLegacy8259, Efi8259Irq0, (UINT8 *)&TimerVector);
 378   ASSERT_EFI_ERROR (Status);
 379
 380   //
 381   // Install interrupt handler for 8254 Timer #0 (ISA IRQ0)
 382   //
 383   Status = mCpu->RegisterInterruptHandler (mCpu, TimerVector, TimerInterruptHandler);
 384   ASSERT_EFI_ERROR (Status);
 385
 386   //
 387   // Force the timer to be enabled at its default period
 388   //
 389   Status = TimerDriverSetTimerPeriod (&mTimer, DEFAULT_TIMER_TICK_DURATION);
 390   ASSERT_EFI_ERROR (Status);
 391
 392   //
 393   // Install the Timer Architectural Protocol onto a new handle
 394   //
 395   Status = gBS->InstallMultipleProtocolInterfaces (
 396                   &mTimerHandle,
 397                   &gEfiTimerArchProtocolGuid,
 398                   &mTimer,
 399                   NULL
 400                   );
 401   ASSERT_EFI_ERROR (Status);
 402
 403   return Status;
 404 }