ArmPlatformPkg/Library/SP804TimerLib/SP804TimerLib.c

   1 /** @file
   2
   3   Copyright (c) 2008 - 2010, Apple Inc. All rights reserved.<BR>
   4   Copyright (c) 2011 - 2014, ARM Limited. All rights reserved.
   5
   6   This program and the accompanying materials
   7   are licensed and made available under the terms and conditions of the BSD License
   8   which accompanies this distribution.  The full text of the license may be found at
   9   http://opensource.org/licenses/bsd-license.php
  10
  11   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  12   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  13
  14 **/
  15
  16 #include <Base.h>
  17
  18 #include <Library/BaseLib.h>
  19 #include <Library/TimerLib.h>
  20 #include <Library/DebugLib.h>
  21 #include <Library/PcdLib.h>
  22 #include <Library/IoLib.h>
  23 #include <Drivers/SP804Timer.h>
  24
  25 #define SP804_TIMER_METRONOME_BASE    ((UINTN)PcdGet32 (PcdSP804TimerMetronomeBase))
  26 #define SP804_TIMER_PERFORMANCE_BASE  ((UINTN)PcdGet32 (PcdSP804TimerPerformanceBase))
  27
  28 // Setup SP810's Timer2 for managing delay functions. And Timer3 for Performance counter
  29 // Note: ArmVE's Timer0 and Timer1 are used by TimerDxe.
  30 RETURN_STATUS
  31 EFIAPI
  32 TimerConstructor (
  33   VOID
  34   )
  35 {
  36   // Check if the Metronome Timer is already initialized
  37   if ((MmioRead32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CONTROL_REG) & SP804_TIMER_CTRL_ENABLE) == 0) {
  38     // Configure the Metronome Timer for free running operation, 32 bits, no prescaler, and interrupt disabled
  39     MmioWrite32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CONTROL_REG, SP804_TIMER_CTRL_32BIT | SP804_PRESCALE_DIV_1);
  40
  41     // Start the Metronome Timer ticking
  42     MmioOr32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CONTROL_REG, SP804_TIMER_CTRL_ENABLE);
  43   }
  44
  45   // Check if the Performance Timer is already initialized
  46   if ((MmioRead32 (SP804_TIMER_PERFORMANCE_BASE + SP804_TIMER_CONTROL_REG) & SP804_TIMER_CTRL_ENABLE) == 0) {
  47     // Configure the Performance timer for free running operation, 32 bits, no prescaler, interrupt disabled
  48     MmioWrite32 (SP804_TIMER_PERFORMANCE_BASE + SP804_TIMER_CONTROL_REG, SP804_TIMER_CTRL_32BIT | SP804_PRESCALE_DIV_1);
  49
  50     // Start the Performance Timer ticking
  51     MmioOr32 (SP804_TIMER_PERFORMANCE_BASE + SP804_TIMER_CONTROL_REG, SP804_TIMER_CTRL_ENABLE);
  52   }
  53
  54   return RETURN_SUCCESS;
  55 }
  56
  57 /**
  58   Stalls the CPU for at least the given number of microseconds.
  59
  60   Stalls the CPU for the number of microseconds specified by MicroSeconds.
  61   The hardware timer is 32 bits.
  62   The maximum possible delay is (0xFFFFFFFF / TimerFrequencyMHz), i.e. ([32bits] / FreqInMHz)
  63   For example:
  64   +----------------+------------+----------+----------+
  65   | TimerFrequency |  MaxDelay  | MaxDelay | MaxDelay |
  66   |     (MHz)      |    (us)    |   (s)    |  (min)   |
  67   +----------------+------------+----------+----------+
  68   |        1       | 0xFFFFFFFF |   4294   |   71.5   |
  69   |        5       | 0x33333333 |    859   |   14.3   |
  70   |       10       | 0x19999999 |    429   |    7.2   |
  71   |       50       | 0x051EB851 |     86   |    1.4   |
  72   +----------------+------------+----------+----------+
  73   If it becomes necessary to support higher delays, then consider using the
  74   real time clock.
  75
  76   During this delay, the cpu is not yielded to any other process, with one exception:
  77   events that are triggered off a timer and which execute at a higher TPL than
  78   this function. These events may call MicroSecondDelay (or NanoSecondDelay) to
  79   fulfil their own needs.
  80   Therefore, this function must be re-entrant, as it may be interrupted and re-started.
  81
  82   @param  MicroSeconds  The minimum number of microseconds to delay.
  83
  84   @return The value of MicroSeconds inputted.
  85
  86 **/
  87 UINTN
  88 EFIAPI
  89 MicroSecondDelay (
  90   IN  UINTN MicroSeconds
  91   )
  92 {
  93   UINT64    DelayTicks64;         // Convert from microseconds to timer ticks, more bits to detect over-range conditions.
  94   UINTN     DelayTicks;           // Convert from microseconds to timer ticks, native size for general calculations.
  95   UINTN     StartTicks;           // Timer value snapshot at the start of the delay
  96   UINTN     TargetTicks;          // Timer value to signal the end of the delay
  97   UINTN     CurrentTicks;         // Current value of the 64-bit timer value at any given moment
  98
  99   // If we snapshot the timer at the start of the delay function then we minimise unaccounted overheads.
 100   StartTicks = MmioRead32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CURRENT_REG);
 101
 102   // We are operating at the limit of 32bits. For the range checking work in 64 bits to avoid overflows.
 103   DelayTicks64 = MultU64x32((UINT64)MicroSeconds, PcdGet32(PcdSP804TimerFrequencyInMHz));
 104
 105   // We are limited to 32 bits.
 106   // If the specified delay is exactly equal to the max range of the timer,
 107   // then the start will be equal to the stop plus one timer overflow (wrap-around).
 108   // To avoid having to check for that, reduce the maximum acceptable range by 1 tick,
 109   // i.e. reject delays equal or greater than the max range of the timer.
 110   if (DelayTicks64 >= (UINT64)SP804_MAX_TICKS) {
 111     DEBUG((EFI_D_ERROR,"MicroSecondDelay: ERROR: MicroSeconds=%d exceed SP804 count range. Max MicroSeconds=%d\n",
 112       MicroSeconds,
 113       ((UINTN)SP804_MAX_TICKS/PcdGet32(PcdSP804TimerFrequencyInMHz))));
 114   }
 115   ASSERT(DelayTicks64 < (UINT64)SP804_MAX_TICKS);
 116
 117   // From now on do calculations only in native bit size.
 118   DelayTicks = (UINTN)DelayTicks64;
 119
 120   // Calculate the target value of the timer.
 121
 122   //Note: SP804 timer is counting down
 123   if (StartTicks >= DelayTicks) {
 124     // In this case we do not expect a wrap-around of the timer to occur.
 125     // CurrentTicks must be less than StartTicks and higher than TargetTicks.
 126     // If this is not the case, then the delay has been reached and may even have been exceeded if this
 127     // function was suspended by a higher priority interrupt.
 128
 129     TargetTicks = StartTicks - DelayTicks;
 130
 131     do {
 132       CurrentTicks = MmioRead32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CURRENT_REG);
 133     } while ((CurrentTicks > TargetTicks) && (CurrentTicks <= StartTicks));
 134
 135   } else {
 136     // In this case TargetTicks is larger than StartTicks.
 137     // This means we expect a wrap-around of the timer to occur and we must wait for it.
 138     // Before the wrap-around, CurrentTicks must be less than StartTicks and less than TargetTicks.
 139     // After the wrap-around, CurrentTicks must be larger than StartTicks and larger than TargetTicks.
 140     // If this is not the case, then the delay has been reached and may even have been exceeded if this
 141     // function was suspended by a higher priority interrupt.
 142
 143     // The order of operations is essential to avoid arithmetic overflow problems
 144     TargetTicks = ((UINTN)SP804_MAX_TICKS - DelayTicks) + StartTicks;
 145
 146     // First wait for the wrap-around to occur
 147     do {
 148       CurrentTicks = MmioRead32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CURRENT_REG);
 149     } while (CurrentTicks <= StartTicks);
 150
 151     // Then wait for the target
 152     do {
 153       CurrentTicks = MmioRead32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CURRENT_REG);
 154     } while (CurrentTicks > TargetTicks);
 155   }
 156
 157   return MicroSeconds;
 158 }
 159
 160 /**
 161   Stalls the CPU for at least the given number of nanoseconds.
 162
 163   Stalls the CPU for the number of nanoseconds specified by NanoSeconds.
 164
 165   When the timer frequency is 1MHz, each tick corresponds to 1 microsecond.
 166   Therefore, the nanosecond delay will be rounded up to the nearest 1 microsecond.
 167
 168   @param  NanoSeconds The minimum number of nanoseconds to delay.
 169
 170   @return The value of NanoSeconds inputted.
 171
 172 **/
 173 UINTN
 174 EFIAPI
 175 NanoSecondDelay (
 176   IN  UINTN NanoSeconds
 177   )
 178 {
 179   UINTN  MicroSeconds;
 180
 181   // Round up to 1us Tick Number
 182   MicroSeconds = NanoSeconds / 1000;
 183   MicroSeconds += ((NanoSeconds % 1000) == 0) ? 0 : 1;
 184
 185   MicroSecondDelay (MicroSeconds);
 186
 187   return NanoSeconds;
 188 }
 189
 190 /**
 191   Retrieves the current value of a 64-bit free running performance counter.
 192
 193   The counter can either count up by 1 or count down by 1. If the physical
 194   performance counter counts by a larger increment, then the counter values
 195   must be translated. The properties of the counter can be retrieved from
 196   GetPerformanceCounterProperties().
 197
 198   @return The current value of the free running performance counter.
 199
 200 **/
 201 UINT64
 202 EFIAPI
 203 GetPerformanceCounter (
 204   VOID
 205   )
 206 {
 207   // Free running 64-bit/32-bit counter is needed here.
 208   // Don't think we need this to boot, just to do performance profile
 209   UINT64 Value;
 210   Value = MmioRead32 (SP804_TIMER_PERFORMANCE_BASE + SP804_TIMER_CURRENT_REG);
 211   return Value;
 212 }
 213
 214
 215 /**
 216   Retrieves the 64-bit frequency in Hz and the range of performance counter
 217   values.
 218
 219   If StartValue is not NULL, then the value that the performance counter starts
 220   with immediately after is it rolls over is returned in StartValue. If
 221   EndValue is not NULL, then the value that the performance counter end with
 222   immediately before it rolls over is returned in EndValue. The 64-bit
 223   frequency of the performance counter in Hz is always returned. If StartValue
 224   is less than EndValue, then the performance counter counts up. If StartValue
 225   is greater than EndValue, then the performance counter counts down. For
 226   example, a 64-bit free running counter that counts up would have a StartValue
 227   of 0 and an EndValue of 0xFFFFFFFFFFFFFFFF. A 24-bit free running counter
 228   that counts down would have a StartValue of 0xFFFFFF and an EndValue of 0.
 229
 230   @param  StartValue  The value the performance counter starts with when it
 231                       rolls over.
 232   @param  EndValue    The value that the performance counter ends with before
 233                       it rolls over.
 234
 235   @return The frequency in Hz.
 236
 237 **/
 238 UINT64
 239 EFIAPI
 240 GetPerformanceCounterProperties (
 241   OUT UINT64  *StartValue,  OPTIONAL
 242   OUT UINT64  *EndValue     OPTIONAL
 243   )
 244 {
 245   if (StartValue != NULL) {
 246     // Timer starts with the reload value
 247     *StartValue = 0xFFFFFFFF;
 248   }
 249
 250   if (EndValue != NULL) {
 251     // Timer counts down to 0x0
 252     *EndValue = (UINT64)0ULL;
 253   }
 254
 255   return PcdGet64 (PcdEmbeddedPerformanceCounterFrequencyInHz);
 256 }