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